I only half explained the destructive interference thing. So I'll explain it better in *text form.* Ooh! Because the pits are 1/4 as deep as the wavelength of light, the light that is reflected back becomes 1/2 its wavelength out of phase with the projected light. This will reduce the intensity of the overall beam due to destructive interference. That's also part of why the change from pit to land is what matters, because depending on how the laser tracks it, pits might very well get reflected more strongly than lands. The pits and lands can be inverted and still encode the same data. There just has to be some concrete change in brightness between the two, which the depth-change accomplishes.
One thing you could talk about is the Double Density cd. I remember that I had one album when I was younger(mid 2003) but I don't remember anything from it, just it was double density and besides my computer, only my DVD player could read the second layer fine
@Howard Black "Does this mean that the lens-to-disc-surface distance is critical?" While it is important it is NOT because of the interference as that happens regardless of the distance. But the distance is important for the laser to focus on the correct distance.
Great video. Back in 1992 I applied for a job at a TV repair shop. They told me I'd need to know about CD players and I had only just bought one from Radio Shack. So off to the library at the college I was attending to read. In one afternoon I learned everything you just covered. About the same time I got into ham radio and found that packet radio systems use the same NRZI encoding and reed solomon for FEC (forward error correction). All Very Good Stuff! Thanks for doing this video.
Are you sure it was FEC? I remember being in my uncle’s place years ago (he was a radio ham) and hearing some digital data communication being monitored on his gear: you could distinctly hear the packet being transmitted, followed by the acknowledgement, then another packet etc. Seemed like a waste of bandwidth. I told them they should do a TCP-style sliding-window protocol, to allow multiple packets to be sent before receiving the acknowledgements, to get around the channel latency.
Fun fact about the compact disc. During the design phase of the compact disc at Philips, they had a meeting about the size of the center hole. Joop Sinjou, head of Philips audio products, grabbed a Dutch 10 cent coin (known as a 'dubbeltje') and placed it on the table and decided that it should be that size. And to this very day, optical disks like CD-ROMS, DVDS and Blu-rays still have the same 15 mm hole since the release of the original CD in 1982.
I can also recall an anecdote about a demo of the compact disc system for the first time, where one of the engineers pulled a disc from the player, spit on it, put it back, and everybody was amazed at the fact that it played perfectly.
* 10mm. It was the first thing they negotiated and it was the easiest thing they could agree about. Other anecdotes about the history of CD are easy to find on the Internet and a little less favorable about the negotiation process. For example, Philips had in mind to make the OUTSIDE diameter 11.5cm, to match the size of the cassette. That way, it would be easy to fit CD's and CD players into e.g. storage systems that were already available for cassettes. And Polygram (the record company that Philips owned) built a factory in Germany with machines to press 11.5cm discs. Sony didn't own a record company at the time, so they were worried that Philips would be at an advantage (and rightly so). So they insisted that the diameter be 12cm "so that the 9th symphony of Beethoven would fit". This cost Philips a lot of time and money. They even already had prototypes (Google for "Pinkeltje") and test discs. Another anecdote: Philips already had the TDA1540 D/A converter which was 14 bits. But Sony insisted that the CD should use 16 bit audio. Philips didn't have time to develop another D/A converter for their first CD player so they had to invent 4x oversampling and put it in their first CD players. Sony originally wanted 44056 samples per second, and Philips wanted 44000 I think (my memory is vague but this story is on the Internet somewhere). They settled on 44100 because it was a convenient multiple of the number of lines in an NTSC as well as a PAL video signal. When Philips and Sony started working together on the CD standard, Sony already had a device to record digital audio on a U-Matic video tape. In the late 1990s I talked to a colleague at Philips Hearing Instruments who had been involved in the development of the CD (he gave me a pre-production Philips CD-100 which I still own and which still works), and he told me some hairy stories about how Philips really did all the development work and Sony just paid for the research and regularly caused massive pains to the development team because they changed stuff that everyone at Philips thought they had already agreed on. I wouldn't be surprised if this was the reason that Sony beat Philips to market with the first CD players. But I also remember that the first Sony CD players weren't that good: they had a standard DC motor with a worm drive to move the laser and it wasn't as fast and accurate as the Philips mechanisms which were based on a linear motor. Nowadays of course all CD mechanisms have worm drives because motors, lubrication, machining accuracy and magnets have improved over the years.
Jac Goudsmit The standard was always 16-bit audio, early 12 and 14-bit DACs simply discarded the extra low-order bits (an absolutely trivial thing to implement in digital logic) simply because it was not practical at the time to implement the logic to utilize those extra bits in a manner that brought you above the inherent noise floor (most people do not realize how low a noise floor you need to actually exploit a 16-bit ADC or DAC). But then most of the anecdotes surrounding the early CD development have been disproven over the years, including the often claimed Beethoven Symphony as the size of CD required to accommodate 74 minutes of music could not have been determined until after the encoding format was defined and the encoding format had not yet been defined at the time that story claims to have occurred (in fact, there were proposals to use encoding formats that would have allowed up to 97 minutes on a 10cm disc also being considered)...too much about the standard had yet to be pinned down at that time even though engineering proofs of concept likely existed since they would need to validate the basic hardware requirements and limits...pinning down modulation and error correction schemes would have logically occurred after the basic hardware premise had been tested.
I remember a CD which was scratched so bad no CD players in our house could play the entire disc. I wowed when the car stereo managed to play the CD just fine.
Neither helps recover data from a scratched disc. Car stereos are just often built like tanks. I had a CD-R that I burned in Disc-at-Once (single session) mode on an old burner that only supported Track-at-Once mode. I'm not sure how that ancient version of Easy CD Creator allowed this to happen, but it completed the burn successfully. Every CD player I had could play the first couple tracks, and if I played straight through, they would go well into the third. But then they would hang and eventually throw an error. But one particular Sony Discman could read the entire disc just fine. I think I later found a PC DVD drive that could also do it. Probably just very forgiving firmware.
I watched a TV show many years ago that had a CD with 8 slots cut into it from the centre towards the edge. You would have though the CD was unplayable and yet it never missed a sound. It sounded as good as an intact version of the same disc.
I just want to say that I'm watching this in 2021 with a brand new BluRay drive in my PC that has now only been used to burn CDs. What a time to be alive.
The CD has been the best media for music imo. Its small enough not to be inconvenient like laserdisc or vinyl, while large enough for proper album art/sleeve to fit with the case. Capacity/quality ratio perfect for a single album of music. Its both hi-tech and old-school simultaneously. When you own an official CD of your fav band/artist, youre connected with them in a way. Theres some old-school shenanigans to be had in the whole process of taking a CD out of the case and popping it into the car audio while exploring the album art and then enjoying the ride to your fav music.
This was super fun to watch! My mom, brother, and I have all worked with CD/DVD manufacturing, so it was nice seeing someone else appreciate how they're made and the process to do it.
@@chitlitlah Most likely around double the size; as the RealVideo codec isn’t as efficient as the H.265/HEVC and VP9/AV1 (which is what UA-cam uses) codecs commonly used for 4K video.
What I love about this channel is how in depth you take everything. There are things that I've always wondered "but how?" You explain it all, right up to the point where I'd almost need an engineering degree to truly understand it lol.
I fell in love with the compact disc format in the '80s. Well mastered releases can sound amazingly faithful and vastly more so than phonograph records. It does wonders for classical and jazz too!
If you have tube amps and high quality speakers as well as a high quality turn table (all analog) and the vinyl is a good press, the first time you play the record the sound will be (theoretically) perfect
You need high quality amps tube or not. You’ll actually have a higher noise floor with the vinyl than with the CD. But I do appreciate a good vinyl album
As an electrical engineer, you have no idea how happy this video makes me. It's so well explained, and you reference deeper concepts in just the right way that I understand where you're going. Awesome video!
I have had a stuttering problem my entire life. I always think it's only me, conveniently forgetting that most of the time I speak fine. When I see the outtakes from creators like the one at the end of your video posted today, it really helps me to feel better. Your delivery makes your videos enjoyable. Thanks for making these videos.
You’re literally answering every single one of the crazy questions I had as a child. People looked at me like I had lost my mind. Glad to see all of your content on UA-cam, it’s definitely much appreciated and brings me back in time.
Why can I only like this once! A fascinating subject, with your perfect balance between technical details and not overwhelming us, and a great sense of humour.
In this context 2s complement is best thought of as a representation rather than the operation. It just makes basic operations like addition easier at the binary level. You can just add -6 and +8 in 2s complement binary representation and get the right sign in the result (also in 2s complement)
For audio, I think 2s complement has some additional benefits not mentioned. In addition to addition, it makes multiplication easier, which makes it easier to add gain digitally and it has a single 0-value
Yep, it's the easiest way to manipulate signed data because it acts exactly like unsigned data that's been shifted by half of the available range. In other words, unsigned audio would have it's silent point at a middle value and signed audio shifts it down to 0. But if we subtract 1, we wrap around to FFFF (65535) so making that represent -1 means signed and unsigned math can use the same binary functions. We just need to know that our overflow (and hopefully clipping) point is now 7FFF in the positive direction and 8000 in the negative.
I love CDs, somehow owning a physical copy of the music I love makes me feel better than just streaming it. But I never really understood how binary code is translated into sound? That’s pure magic right there.
@etchatails the ease of piracy is actually why i don't care for CDs as a physical medium. Anyone can burn a CD, and to me it makes them less interesting. Bootlegging vinyl on the other hand, requires highly specialized equipment and i imagine if that technology becomes affordable and compact enough for the average music aficionado to acquire, vinyl will fall back out of favor. Easily reproducible media just doesn't feel as legitimate or collectible.
@GeebusCrust ehh. I see your point however bootlegging cds doesnt feel the same to me. For one buying the CD officially gives you the cd slip and usually a printed cd with nice art. That matters to me, i hate the look of blank cds with titles written on them in sharpie. So it is easy to pirate CDs but the art on the slip and the disc itself motivates me to buy from official sources and serves as a point that enhances the music for me (IMO). I suppose someone with a printer that does CD printing could just print the art onto the blank CD but alot of cd slips I have contain such personal touches from the musicians that it adds to the experience for me.
A total aside but when I was helping a young friend write their first university essays I actually loaded up Wikipedia. They instantly said you can't use that, the Prof was clear on that. Then I showed her my dirty secret. The Reference section. If the information you want is there and it is cited you can use the source and the source will usually have much more information than Wikipedia. She thought that was amazing. I then took her to a reference library and helped her work through that. She had gone to a High School in another country that was primarily artistic so essay's weren't really a thing like they are here. She was going to an Arts School for university but still had to take humanities. When she handed her first essay in her prof saw the physical books mentioned in the Bibliography and asked her why she didn't just use the internet. I don't have much faith in that school... The rest of this video is fascinating.
I usually did this, and Google Scholar/Books, and our university's online library look-up system. I initially search Wikipedia for relevant sources, then Google Books/Scholar, and cross-reference if that publication is available in our uni library. My fellow students and some professors were always confounded how I read or found these sources as if I read through the whole uni library knowing everything. My professors were more fond of physical sources that could be found in the library. Since Google books also didnt show the whole book, I also read the entire relevant chapter(s) if it was available in our library. This gave me more sources available than what I can gather online and looks much more credible too. Took a bit more work but it really paid off and is much more efficient than just poring though the library randomly searching that even metadata doesn't help as much.
Hi Alec, Coming from a Computer/ Communications / Engineering background, I read about these technologies as they were introduced to the world. It still fascinates me that there is so much attached to these formats by way of belt and braces /belt and suspenders technology. Unless very interested in it, the last 15 years have seen people ignore the ‘magic’ behind the technology, preferring to accept that the stuff in the box works. Thank you for deconstructing the myths and legends behind this everyday technology!
EXCELLENT video! In the 1990s, I worked at a company that made CD-i productions and I'm pretty familiar with all the stuff that you mention in the video. When I started watching, I thought I was going to have to point out a bunch of mistakes but I was pleasantly surprised! I have nothing to add to the video; you even got Kees Schouhamer Immink's name almost right (his first name is pronounced "Case") :-)
The CD was a marvel at the time - and the audio quality is still the gold standard for listening experience in stereo - simply cause it is 'good enough' for all human ears. But we moved on and now with flash-storage got a medium that is not as long lasting, but far more convenient.
Longevity is largely dependent on the original quality of the media. I've got twenty year old N64 carts that still have games saved on the flash memory, while there are Saturn games of similar vintage that are succumbing to disc rot.
ThetaReactor No, i am talking about the limited lifetime of data saved on flash memory. N64 cartridges got a battery to keep the savegames. If that runs out the data is lost. In SD-Cards the data is stored in the form of charging the gate of the mosfets and those too will slowly discharge. They both have a rather short limited lifetime even under good conditions. A CD on the other hand will last for many decades when stored correctly. But under the "right" conditions can be dead within a few years even.
Most people also forget or don't know the fact that a computer's Solid State Drive is very similar to a flash SD card like is used in phones and cameras. They are all limited in life in some way. SSDs don't have to worry about any sort of charge in the way the old console memory cards did, nor like the SD cards - They're limited based on write cycles. Ever look at the warranty info for a Samsung SSD? "5 Years or 75TBW" They are saying it'll last AT LEAST 5 years or UP TO 75 Terabytes Written. Once you hit the TBW threshold, your drive is soon to give way. SSDs that fail prematurely are simply faulted due to some sort of defect. (840 Evo SSD in my gaming rig, 4 years and still going strong at just under 20 TBW) But that ^ Up there sure explains why some of my SD cards have been totally dead after a long period of time of not being used
@@morgfarm1 The Nintendo 64 kept save game data in a replaceable memory expansion pack. I believe you meant to refer to Gameboy cartridges which were forced to tie data to the remaining lifetime of the button cell. Later versions were upgraded with writable flash memory. though
@@net28573 I could well be wrong, but I do remember the 3V button cell in the old cards. Flash drives that we see today still can fail to a loss of internal charge if left unused for too long is what I understood on another topic. That would explain the 4 dead SD cards I have that weren't used much. Though more recently my SD cards have failed by reaching the written data limit. How much that was im not sure but it was in a dash cam for about 8 months before it croaked
The stack of blank CD-R's in my basement are cheaper than a better FM transmitter, so I still use CDs for playing music in my car since it's only got radio and the wonderful 6-disc CD player integrated. It works well, and it's honestly really convenient since I don't have much songs
I love my CDs. You're going to be very hard pressed to find a similar or better quality digital copy of music without ripping straight off the CD, at least legally. Not only that, but the liner notes and photos gives you so much material, as opposed to digital files, which could be deleted on a whim.
Personally i just want uncompressed audio. Streaming is all lossy compressed. I usually create carefully done FLAC rips of my CDs and add id3 tags to it, including album artwork. The best of both worlds. The album being available as lossless files but also as physical copy in the collection that you can touch and hold in your hands.
There were a lot of optical media formats that tried to have higher quality audio than CD (the ones I can think of off the top of my head are SA-CD, DVD Audio, and Blu-ray Audio), but unfortunately none of them ever caught on.
@@AskDrannik The DSD codec itself (SACD) kinda did catch on though, you can either stream or download DSD audio streams or files currently, and even higher-res variants of DSD than DSD64 (SACD-quality) are a thing in the form of said streams or files.
CD's were one of those "You had to Be There in the 80's" things to really appreciate what a breakthrough the format was. We have several generations that grew up with CDs and Mp3's that take it for granted. I remember seeing a few Dualdiscs in the mid 2000's but never bought one. I heard stories of Dual Discs getting stuck in slot loading car players, and some CD changers couldn't play them because they were too thick to load.
This is amazing. Sometimes, in order to see how far we've come, we have to look back at where we've been. High capacity micro-sd cards never cease to blow my mind. May as well be alien technology compared to what we used 20 years ago to store data.
I like all the video examples they show in this channel: they are always sleek, attractive and originals. Also the content of the video is top notch in term of meaning and how is constructed the explanation, a really great job. Thanks a lot for your great work.
As a technology, I still find the compact disc a marvel of ingenuity, largely because the way information is stored on it. And the players used to convert that information via a laser pick up, into almost perfectly reproduced sound. It certainly did revolutionise the way we listen to music. And I am even more astounded by Mini Disc, that also allows the user to record, and re-record music on a disc that is half the size of a CD, yet with recorders equipped with a long play/record facility, you can store four CD's worth of music, on a tiny pocket sized disc. And don't get me started on Hi MD players, that take the medium even further. Truly amazing stuff, and amazing ideas.
I would like to know in a future video what are the differences between an original molded CD, a blank CD-R (with the process of writting data to it by a CD-Burner), and a CD-RW wrighting process which enables the rewriting of data on the same disc, and why not all CD drives are capable in reading the CD-RW properly. Thank you and cheers from Romania.
CD-R uses organic dyes that can have the reflectivity changed with laser heating. CD-RW uses tellurium suboxide that somehow can change states of reflectivity with laser heating.
I don't know what the materials are called but CD-RW is based on heating up the material in such a way that it either crystallizes or not. The crystals have a different reflection or refraction and if the reader is properly designed, it will see the difference. CD-RW is not compatible with the original specs for CD players, so CD players that predate CD-RW won't play them.
Jac Goudsmit In many respects CD-RW functions much like LCD, the difference being that one changes the crystal state electrically (to rotate the crystal) and the other uses differing levels of heat to change crystal state semi-permanently. As for the main reason that many older CD players could not read CD-Rs, it typically came down to beam intensity. The typical CD-R dyes were usually pretty dark and so you needed a much more powerful laser beam to actually transmit enough light into the disc in order to get an adequate amount of light back out of the disc due to the very lossy transmission medium. Early CD players were designed for the highly reflective pressed CDs and their intensity was often intentionally turned down to help extend the life of their lasers. The lifespan of a laser diode is directly related to how hard you drive the laser and early laser diodes were both less efficient and not nearly as reliable long term, but especially if driven at higher than necessary power levels...and a CD player would be expected to provide many thousands of hours of life during its operational life. In fact, this is what held back Blu-Ray/HD-DVD development by up to a decade while they waited for a blue laser diode that could deliver enough hours of life to be a practical home entertainment/storage device (without needing its laser replaced every few movies/discs) - the main players recognized what a blue laser could mean in terms of increased data storage capacity the instant the blue LED, then laser, were invented, as it was the wavelength of the laser that limited data and track density on a CD, but they could not implement a consumer product that exploited that capability until blue laser diode operational life could be sufficiently extended.
Before I say anything else, I just have to compliment you and say that you seem really comfortable with these recent videos and I love the subtle and not-so-subtle jokes peppered into your scripts. I was glad to hear you get into the corrective elements of the compact disc, as it's one of the most impressive and interesting elements to the design of CDs in my eyes. They saw an inevitable problem and they engineered ingenious solutions.
The good thing is, if you are limited on space, you can streamline your CD/DVD collection to be as specific as you like cheaply. Then "everything else" can be left to streaming services. Eventually you have shelves full of special editions and limited versions and releases that have not or will never appear on a streaming service.
Man, I must be getting old. I remember lots of the "vintage" technology you discuss back when it was new. VHS? Yup. Laserdisk? Yeah. CD? Yes. I had an 8-track player in my bedroom, and I remember listening to Sonny & Cher, the Grateful Dead, KISS, Deep Purple, etc. My Dad had an 8-track player, and a CB radio, in his '73 El Camino. I remember the switch from 8-tracks to cassette tapes...so yeah, I'm THAT old...LoL
I have heard from people who were working with Philips at the time that one of the primary things Sony brought to the table was the actual manufacturing process. Not just a size change to slow Philips down, but the idea of pressing the lands into the plastic layer itself. Thus negating the possibility of Disc Rot, something that Sony engineers had feared would happen with sloppy manufacturing processes. Turns out they made a good move with that, as you have already covered the horrors of Disc Rot previously.
While less susceptible to disc rot than Laserdiscs, CD's aren't completely immune. No doubt the varnish coating and a single-sided disc is cleaner and less prone to issues than the glued-together Laserdisc, but there are cases where CDs have been destroyed from rot, often by a fungus that likes to eat aluminum iirc. That said, it certainly is a better design I think. Though humorously the DVD is constructed rather like a Laserdisc, even on single sided discs. With some DVDs being around for more than 20 years (and still working, I presume) it seems to me that the Laserdisc's rot-prone reputation was always due to sloppy manufacturing. I'd hazard a guess that the non-digital nature of LD made people more careless around it, and the stringent clean-room conditions required by CDs and DVDs weren't followed. And, just to press your buttons a bit, keep in mind that *the worst* Laserdisc manufacturing plant for rotting discs was run by Sony!
Technology Connections I've never encountered disc rot in my life, and I have CDs in my library that were pressed as far back as 1987. All CDs still play just fine, no skipping at all. The only skipping I encountered is from burned CD-Rs. I always assumed disc rot was a myth. I think it's just very rare.
It's just as well Sony DID get on board. If it were left to Philips alone, Ugh! What a gosh-awful mess the CD would've been. For this reason, I give ALL the credit for creating the CD format exclusively to SONY!
DVD is constructed exactly like two CDs glued back to back to each other - the pits are moulded into the outer plastic layer that is then mirror-coated. Except half as thick. If the resin holding together the halves is any good, it stands absolutely to reason that DVDs would last as well as CDs and then some.
CD-Rs of olde were terribly plagued with disc rot, I remember very well the pirate (oops) "BACKUPS" of early 2000s would go bad by mid 2000s. Never seen it with pressed discs tho indeed.
I've never seen such a positive comments section with so many smart people. I just started watching this channel a few days ago but I'm blown away by the knowledge and friendliness flying around here. I am learning so much about things I never even cared to question so thank you for these amazing videos and inspiring in me a desire for more knowledge.
“And then we’ll relish in the fact that everything is on the internet now”; that with the vinyl jab had me rolling. Extra disgruntled in this one?! Ha ha
Speaking of audio quality, Alec: I have some constructive feedback (pardon the pun), if your workflow supports it: The placement of your mic works quite well for maintaining consistent volume, but the proximity to your chest means the 200-800Hz range of your voice is about 10 decibels louder than the rest, which makes you sound muffled in comparison to other UA-cam creators. May I suggest that you cut that range by 6-7dB before you normalize the audio level on your next video? This will greatly improve intelligibility at lower volumes, at the cost of raising the noise floor slightly. Always appreciate your videos, by the way. They're always clear, well thought out, and entertaining. Keep doing what you love!
Another great video! I find it fascinating that the actual data is encoded in the plastic, not the aluminum. As for the CD being obsolete I would beg to differ. There really isn't a decent mainstream way to purchase fully lossless audio today. Sadly I don't think the demand is really there for it. The younger generation today doesn't really understand the difference, and seem to be content listening to compressed audio through earbuds. I grew up in the era of big speakers and amplifiers, and the birth of the CD. To this day I still enjoy playing my CDs on a real stereo system. That will never be obsolete to me.
I totally agree with everything you said there, and yes how young people now are happy to listen to their music on a tiny mobile phone speaker! And don't even get me started on the sound quality of DAB radio!
It may help to understand that the aluminum layer is vapor deposited (an *extremely* thin layer) onto the plastic CD disc after pressing - so, in a sense, both the plastic disc and the aluminum carry the information as the aluminum is simply applied to the surface of the plastic in order to provide the optical reflectivity that the player needs to effectively see the encoded data in an efficient manner. As such, both the plastic disc and the aluminum reflective layer reproduce the lands and pits, it’s just much easier to bounce light off the highly reflective aluminum layer.
It really bothers me how the industry essentially leapfrogged to streaming before implementing a mainstream and popular way to download proper lossless... sure, some sites offer it, but they are not the big places the general public would necessarily think of to go to download music, and the number of sites can be counted on 2 hands. Now that they’ve marketed actually downloading anything as unfashionable and the old way of doing things, nobody even cares anymore. It’s disgusting.
*Anona Mouse:* Very well said. Additionally, downloadable media is sometimes subject to contract and litigation. That mp3 might be yours to keep because you paid for it, but if you need to restore that data and you can't because someone had an argument with Amazon or iTunes, or a country, you're out of luck. Provided that the CD (or any physical format) hasn't been degraded, you will always have access to it. EDIT: Or the player that reads it.
@@Christopher-N All my CD's got transferred to my SSD via EAC (Image copy). I used Audacity to divy up the single track into songs, and Flac to compress the finished product. Then I made backups. Now I am immune to CD rot and CD player failure. SMH at the fact that vinyl is making a comeback. They should bring back wire recorders while they're at it.
@@Dynamic_Editor Dynamic range. The loudness war left many casualties behind. I'm also no fan of craptastic MP3's. With storage and bandwidth as cheap as they are, the worst we should be encoding are highest bitrate VBR MP3 while FLAC should be the default.
Andreas Vollenweider! Ah, this brings back memories of artists like Don Dorsey, Patrick Moraz, Michael Hoenig, Craig Anderton, the Nightingale collection, etc. My dad is an audiophile and had tons of the Telarc and CBS collection samplers. Synthesizer music reproduced in pure digital and played on Klipsch speakers was absolutely magic in the 80's. Most CDs back then had a designation "DDD" which meant the pipeline was all digital from the synth directly to the recording computer. No line noise at all, bright treble, and no evil "bass boost" to be found. Such a great privilege to be alive when all this tech was brand new! Did I ever mention how much I love your channel? Cheers!
Be careful when throwing the word "obsolete" around. Passive media is never obsolete as long as there is a machine to extract information from it and someone who is interested in said information. :)
yeah but DVDs are way more reliable. CD-Rot is very common, while not so much on dvds. Still, i wish there was a cheap consumer data tape alternative which could at least do 50GB. DVDs are too small and not cheap enough to justify not buying another hdds for archiving. And blurays are just too expensive and no one has them.
There used to be a lot of consumer data tape alternatives. I've used them to archive projects from my A/V workstation back in the day. Going back to something I archived 20 years ago is a crapshoot. Sometimes I'm successful and sometimes I'm not. A lot can happen to the bits stored on those tapes over time.
Not to mention as long as new compact discs continue to be made. It's not like compact cassette where, although you can technically still buy a new deck, it's going to be crap because the dolby noise reduction technology is no longer being licensed to them. CD rot is insanely rare and apart from that one plant producing bad pressings for a couple of years, so it's barely even worth taking into account. Honestly, the biggest strike against compact disc is the loudness war, and that's a whole another topic entirely - one that wouldn't make a bad subject of a video in itself, really. There's a lot of misconceptions regarding the quality of CD vs vinyl that really need to be set straight.
5:32 I love this part of the video! I watch this video all the time, and it's this Dirty Harry reference that makes me remember that I've watched this already, many times. Your explanations are very easy to understand btw!
Two's complement shouldn't hurt your brain. To encode the negative of a number, invert the bits of its positive value representation (this is one's complement), then add 1 to the resulting binary value (this is two's complement). Decoding works the same way, first invert all bits, then add 1. The add one is to avoid having an encoding for negative zero (note that some other encodings do allow for negative zero for various reasons), and overflowing then also is 'natural' (zero to maximum positive, then minimum negative to -1, and then zero again).
The reason to use it, is that in the microprocesors , you can add and substract with the same digital component, that is an adder. The adder can add or substract , just because it's an adder that can take a negative number as an argument. The circuit becomes super simple and makes no distinction with any number , negative nor positive.
@@intron9 Yep, that's the 'natural overflow' part. The increment/decrement/add/subtract operations do not need to know if it's an unsigned or signed value that they are operating on. A trick to get the maximum unsigned value of a given sized type in languages like C (apart from using macros like UINT_MAX) is to cast -1 to unsigned, since unsigned zero "underflows" to the maximum unsigned value when decremented and this is the same binary representation as -1. Also, incrementing negative values does the right thing (which would not be the case if the most significant bit would be interpreted as sign and the rest of the bits just the positive value representation). Also note that this is the reason why the negative numbers can represent one more value (e.g. signed byte is -128..+127), since zero (0) is part of the positive numbers (128 values: 0..+127), but the negative numbers do not need to represent zero (128 values: -128..-1). Same applies to 16-bit, 32-bit, ... integer representations similarly.
I like to think of the principle like a mechanical car odometer or tape counter: If you go backwards from 000, it rolls over to 999 and goes backward. 995 is equivalent to -5, 990 to -10, and so forth. This is the decimal equivalent of the same principle, called nines' complement. Subtraction with nines' complement arithmetic works the same way in decimal as with twos' complement in binary. Many mechanical adding machines (used back before electronic calculators became affordable) used this to allow calculating subtractions even with a mechanism that could natively only add. To compute a difference, you could simply add the nine's complement of the number to be subtracted, then add 1. (As a side note, I find the naming oddly inconsistent. Logically it should be either ones' complement and nines' complement, or twos' complement and tens' complement, but not twos' complement and nines' complement. Oh well.)
I really really enjoy your videos. They are educational, informative, yet still light hearted and funny. I love the bloopers at the end, they show a humble guy just having fun with his UA-cam channel. Keep it up. I'm Patreon'ing you cuz you are just so likable and geeky and fun.
I knew a lot of this, but it's still really awesome to have you explain it as you do. It's like you fill in the pits in my own brain with useful information. Wait, would that blank out my mind? WHAT ARE YOU DOING?! Seriously though, good video! Also I wanted to give props for saving your "like and subscribe" for the end of the video. I don't think enough people express gratitude for doing that. I've been subscribed for a while, but look for me soon on your Patreon page. :)
Physical media, undesirable? Unlike with streaming, you keep it after you pay for it, and the copyright holders can't revoke your access to it. Physical media, while sometimes bulky and subjectively inconvenient, is objectively better.
I think the bulkiness adds to its appeal. There are a lot of people who prefer bulkier books to their digital equivalent to showcase how much they're reading. It's almost a status symbol. I plan to acquire more physical media in the future since there's not much difference in price (often the physical being the cheaper option thanks to lobbying) simply to show off them. I might even invest in either an internal or USB Blu-ray drive, I still keeping my DVD-burner in my PC since it doesn't impact anything but I still have a lot of CDs and DVDs. I plan to publish my games on CD or DVD, and since my engine is so space efficient (and will be even more so once I finish porting the compression algorithms to D) I might use the 80mm CDs or DVDs for their retro-futuristic feel (I still have a very rare 80mm CD-RW, my favorite disc).
Very true. I still make a point of buying CDs, and then ripping them for convenience and portability. But I still have the physical media, unlike an iTunes download.
CDs also can't be suddenly removed from your collection because a contract was up. And they still work if your Internet goes out. Edit: Oh, and they're not at risk of getting corrupted like other writable media is.
Great video! I wish you had more "connections" between techs like James Burke did with history with his show. I hope you cover more on error correction. It's amazing LDPC and turbo codes are used in consumer applications these days.
Amazing videos, truly a treasure on UA-cam! Also, I still go to a used CD store and rip my own CDs to flac files rather than buying my music online...partially for quality (compared to mp3s) but also partially money. So yeah 🤷
Protection of the file is what CD is all about.Without the protection the sound quality will degrade over time.The only way to protect a flac file is to burn it to an M disc.
@@fraudsarentfriends4717 How can the sound quality of a flac (a lossless format) degrade over time? Or you worry about degradation happening in an hard disk?
The Compact disc is the evolution of the Audio Long Play project. a group started by Phillips engineers in 1974 to develop an audio counterpart to the Video Long Play project AKA LaserDisc. As it turns out, using optical discs to store analog audio better than the human ear is crazy difficult. So they made the decision at the end of 1975 to switch to a digital format with error correction, which they developed over the next few 3 years into the Compact disc. On March 8th 1979, this format was shown to an audience of uninterested Japanese executives. That is, except for one group of executives from Sony, who were working on their own digital audio disc. Together they would refine the Compact disc over the next year, finally bringing it to market in late 1982
As someone who has been repairing speakers for years, setting up countless sound systems and building my reference system over the years, I can confidently say that CDs are superior to records.
@@schragemusik oh that makes sense. Haha long live CD. Now the part you may disagree with is my preference for upmixing 2 channel music. I use DTS Neo X primarily but I also have had good results with Logic 7, THX Neural and Dolby Pro Logic 2X. These don't steer instruments around the room (which is unrealistic), they extract the reverberations, reflections and ambience present within the original recording and place them to the sides and back of the room where they belong. It's very enveloping and not gimmicky.
Down the wormhole of Tech Connect videos I go again. By the end of the quarantine, I would have watched all of your content, plus TechCon2's stuff... Which is only a good thing, because this content is so good.
Living near Eindhoven (aka the place where philips started) I heard a lot of stories from people who worked on different philips projects. Last month I talked with someone who worked on the cd-i. Growing up in the early 00's I learned how cd's work at the age of 8 (simplified).
A great video, looking forward to the rest of the series on the wonders of the CD. It was very interesting the whole encoding/decoding & error correction methods used by CD players and what's done even before it's sent to the CD players DAC, those people at Philips and Sony who designed the CD were some smart cookies! Especially for 1980's computer technology!
This is your best video that I've seen. On every level. period. Thank you! Please keep up the good work, I really enjoy your insights, sarcastic comments, and dry humor :)
Thank you so much for your video , I couldn’t believe that one day I have to show it to my child because he doesn’t know how CD used to work. There was a question on it in his homework. Thank you 🙏
I have a hard time accepting that Compact Disks are obsolete. I use them semi frequently at home (mostly for retro computing). Many of my computer gaming buddies simply don't have a optical disk drive in their gaming PC's. I could not fathom being without an optical disk drive. As you said, they were (and still are) an amazing piece of technology.
I mean, they have their uses, but in the grand scheme they're next to dead. Most high-end laptops are abandoning them. CD players are increasingly rare in cars. And aside from their utility, 700 megabytes is just nothing these days. I wish it wasn't dying as an audio distribution format, but unless they get a retro resurgence like Vinyl and Cassettes have (which you never know, they might) I'm thinking they'll just sort of teeter on the edge of darkness.
I think of Blu ray as a spiritual successor, and is a cost effective way of distributing very large quantities of data, such as high resolution films. Although I expect even Blu ray will die off once broadband technology to every home is reliably over say 50-60Mbps. We're nearly there in some places, just not quite. (edit out redundant text)
Key operative phrase "retro computing" not so much audio. Disks, with the physical technology i.e. moving parts just are not as fast nor as compact as USB and TransFlash with a whole terabyte of data, as Bullwinkle would say, "All on this itty bitty card", Hell I do so much with so many different formats, I got a USB floppy drive as well as an external CD/DVD/Blu-Ray drive My main stereo system is still analog in terms of the amp, sub and speakers. Nothing does bass like a bigass subwoofer or highs like an HF horn
CD's are still being released for music, though I suspect mostly for classical music these days. Pure CD only players are hard, if not impossible to find, about the same for DVD. However you can still buy BD players, and they are fully backward compatible with everything stamped onto a 5.25" optical disk (except for those CD-LD combos in that size).
Gotta admire your dedication to matching up the run-time on the VCR with the video's run time at 14:54 when you say "and that's where we hit pause" (OK so I think it's about half a second off but still...)
I love CDs, I rip them to FLAC for use in my house and 256 kb for use in the car. All my CDs are dumped on my NAS and the stereo in the kitchen and living room can pick it up.
@@Dontcareaboutoffending Yep. I like to have a physical copy. So if my internet is out, I can still play it back. I'm on satellite internet where I live and it sucks.
"But being this is a 120mm compact disc, the best audio format in the world and would blow your socks right off, you've gotta ask yourself one question: "Do I feel lucky?" Well, do ya, punk?"
It's mind boggling how people were able to create these complex technologies. I can barely understand it and I wouldn't say I'm stupid, but to conceive of these concepts such a long time ago takes some incredible intelligence.
Minor quibble: A hard disk containing files is also a continuous stream of bits. There's no practical difference between what a computer does to display audio CD tracks as files and what it does to display regular filesystem data as files, apart from not having a name stored. A simple disk filesystem also has the equivalent of a table of contents describing byte offsets at which to find file start positions as well as the lengths of each one.
Hard drives can come with multiple platters, so the data is not necessarily one continuous stream on a single platter. Table of content varies greatly with hard drive with distributed TOC with journaling like NTFS/EXT3+ vs simple local like CD/FATx.
Yeah, my first thought after hearing that is, "You just described a filesystem". It's a very simplified, OS 101 filesystem, but a filesystem nonetheless.
I think the point here is that Windows' "Track01.cda" is a logical construct that is completely virtualized. They aren't ".CDA" files on the disc, they're just ranges of raw samples. Those old enough to remember MSCDEX days can tell you that an audio CD does not present a file system to the OS. Although I suppose you could turn that around and say the the "file system" on CDDA discs just isn't supported by MSCDEX and DOS. This all gets very theoretical at some point.
Not quite. Unlike a CD, the magnetic disk is not written as a single contiguous track. Each track is a closed loop. Then there are multiple heads, one per surface.
CDs were designed for audio first, and general data files (CD-ROM) later. DVDs were designed to be a computer data format from the beginning, with a proper computer file system (actually two, ISO-9660 and UDF), with all the actual applications (DVD-Video, DVD-Audio etc) being done basically as file formats on top of that.
Great job spitting out that bit on two's complement. That was fun. Great job on simplifying the destructive interference thing as well. A little over simplified, but good enough for understanding. And finally, your blurb on wikipedia research is SPOT ON. I started doing that almost as soon as wikipedia launched. I did the exact same thing, too, when someone "reminded" me I couldn't use wikipedia, I would just scroll to the bottom of the article and point.
Excellent video! I remember buying my first CD player in 1988. It creeped me out to have dead silence between songs because I was so used to tape hiss. I'm excited to see upcoming videos. VCD (or Video-CD) was very common in Taiwan around 1999 to 2001 (movies on two CD-ROMs). Taiwanese people weren't very interested in buying "players" for anything. I moved to Taiwan from Ohio in 1996 and I've only met one family who had a VHS player/recorder, and nobody had an answering machine. It wasn't until PC-compatible DVD drives became affordable/available that DVD really took off. (In 1998, I watched the first "Star Wars" movie on LaserDisc at a rich kid's house, which was actually my first LaserDisc experience.)
Anyone remember that rootkit controversy when Sony installed some software on the optical disc? Philips piped up to add their penny's worth to state that because it didn't follow the red book standard (it had file data - the rootkit installer) it could not be labelled as 'Compact Disc Digital Audio.'
Yeah, i remember that and Philips were right, you cant just change things and not follow the standard, if you dont follow standards you cant know it is compatible and everything is thrown out the window. We would end up with products that might work sometimes and sometimes not, a CD player that cant play some CD´s, a certain car that wont start if it has fuel from a certain brand in the tank etc, it would be absolute tech hell.
It has nothing to do with breaking the red book standard, as far as I can tell. Here's some information on the topic: en.wikipedia.org/wiki/Sony_BMG_copy_protection_rootkit_scandal
@@xerzy It has. If the disc contains anything other than Compact Disc Digital Audio, it cannot use that logo as it breaks that particular standard. Sony/BMG *did* label it as a CDDA, including using the logo and was wrong to do so. Philips put in their comment to point out a fact.
The first CD I bought was Olivia Newton-John's Totally Hot. I remember being blown away by how much more treble it had than the cassette version. It convinced me to upgrade almost my entire music collection, AND put a CD player in the car! Fun times.
The pit depth noted may have been correct. Recall that the very first CD and videodisc players used Ali Javan's helium-neon gas laser operating at 632.8nm because the cheaper and simpler aluminum gallium arsenide laser diodes operating closer to 800nm were not yet available in quantity.
I do not believe any CD players use He-Ne lasers, except perhaps in the experimental stages. In any case the referenced wavelength in the document I found was something like 530 or 550nm, way way off from either the 780nm of solid state infrared or the 632.8nm of He-Ne.
Technology Connections A good technical article I came across while verifying my understanding of how the decoding is done (I always try to validate my understanding before replying to technical questions) on *The Physics of the Compact Disc*: leung.uwaterloo.ca/CHEM/750/Lectures%202007/Lect%20Mat/physics%20of%20cd%20pe930103.pdf
The wavelength 500 nm is correct, since that is the wavelength of the light in the polycarbonate medium. In vacuum or air the laser light’s wavelength is 780 nm; divide that by polycarbonate’s refractive index of 1.55 and you get about 500 nm. This also explains the pit depth of 120 nm, which is one-quarter of this. In effect, light is “compressed” or “squeezed” in a medium with high refractive index.
@@pmonta the laser wavelength doesn't change when it enters a medium with a different refractive index. That would violate conservation of energy. This is only possible with things like nonlinear crystals which do second harmonic generation by effectively summing two photons together. None of that happens in plastic.
@@Muonium1 The frequency doesn't change, so there's no change in energy, but the wavelength does change. The first section of Wikipedia's page on "refractive index" has some discussion.
I like the way CD's work, but I think that a good, clean, well pressed and mastered vinyl record, played on a good equipment sounds better than a CD in the same conditions. Just love your channel, Alec!
"Use your imagination" for the "Big Hair" slide? Really? There's a billion Glam Rock/Metal (or Hair Band) images out there that easily got the point across. :)
Trouble was, very few were public domain and/or could be used with attribution. Plus, even if I found a suitable picture, some people would complain about whatever band I chose. So I just left it up to you.
Ahh, got it. Found some that would work, but they all sucked and didn't prove a point. :) I'm surprised that something so ...err.....big..., isn't so easy to find without hurdles, and while anything copyrighted can be used under "Fair-Use", UA-cam is horrible at that, so yeah, upon research, your way was the way to go. (Curse ContentID!)
I'm coming from the hard disk industry and what impressed me most was the actuator arm being able to exactly position over each track. A respectable feat in a lab but to do it in a hand held portable inexpensive consumer product, wow.
There aren't any "tracks". It's one continuous spiral. There are two positioners, the coarse one (usually a stepper motor winding a screw) moves the cradle roughly under the target, and a voice coil within the cradle that finely positions the laser. Hard disks are now up to 12 TB. That fact melts my brain every time I think about it.
I greatly appreciate the reverence for older technologies demonstrated in these videos as well as the humorous asides. Well done! Your technical explanations are a breath of fresh air. Here's a random thought I had for you to ponder for your next video project: DVD Recorders. After you've finished recording your old videotapes to DVDs what other use can they serve besides playing DVDs? It might seem a bit silly, but I recently repurposed my recorder to play a collection of MP3 disks I had made a decade ago. By cobbling together an old PC subwoofer, an old CRT TV, an old pair of speakers and the recorder, I've essentially created a new sound system. It's a bit clunky, (I have to turn on all three devices individually first) but it works well and the quality of the sound is decent.
The pit depth on a CD is about 120 nano-meters, worked as a Process engineer for 15 years in a CD two different CD mastering companies.
You worked in a CD? wOW
@@dynomar11 Your joke fell flat, friend.
@@oeljay as flat as a CD
@@dynomar11 Basically 2D.
It is true, i was the CD
I only half explained the destructive interference thing. So I'll explain it better in *text form.* Ooh!
Because the pits are 1/4 as deep as the wavelength of light, the light that is reflected back becomes 1/2 its wavelength out of phase with the projected light. This will reduce the intensity of the overall beam due to destructive interference. That's also part of why the change from pit to land is what matters, because depending on how the laser tracks it, pits might very well get reflected more strongly than lands. The pits and lands can be inverted and still encode the same data. There just has to be some concrete change in brightness between the two, which the depth-change accomplishes.
Technology Connections Nice!
Yes, which is why the lens is floating and tracks the disc. We'll see more of that in the next video!
One thing you could talk about is the Double Density cd. I remember that I had one album when I was younger(mid 2003) but I don't remember anything from it, just it was double density and besides my computer, only my DVD player could read the second layer fine
@Howard Black "Does this mean that the lens-to-disc-surface distance is critical?"
While it is important it is NOT because of the interference as that happens regardless of the distance. But the distance is important for the laser to focus on the correct distance.
what was your original training? / education?
Great video. Back in 1992 I applied for a job at a TV repair shop. They told me I'd need to know about CD players and I had only just bought one from Radio Shack. So off to the library at the college I was attending to read. In one afternoon I learned everything you just covered. About the same time I got into ham radio and found that packet radio systems use the same NRZI encoding and reed solomon for FEC (forward error correction). All Very Good Stuff! Thanks for doing this video.
Are you sure it was FEC? I remember being in my uncle’s place years ago (he was a radio ham) and hearing some digital data communication being monitored on his gear: you could distinctly hear the packet being transmitted, followed by the acknowledgement, then another packet etc. Seemed like a waste of bandwidth. I told them they should do a TCP-style sliding-window protocol, to allow multiple packets to be sent before receiving the acknowledgements, to get around the channel latency.
Lawrence D’Oliveiro that could have been pactor. It had a very short packet then an ack or nak. Very rapid fire.
I use TNT to send my packets. Very reasonable.
The Nrzi party and A00lf
Fun fact about the compact disc.
During the design phase of the compact disc at Philips, they had a meeting about the size of the center hole.
Joop Sinjou, head of Philips audio products, grabbed a Dutch 10 cent coin (known as a 'dubbeltje') and placed it on the table and decided that it should be that size.
And to this very day, optical disks like CD-ROMS, DVDS and Blu-rays still have the same 15 mm hole since the release of the original CD in 1982.
Joop
I can also recall an anecdote about a demo of the compact disc system for the first time, where one of the engineers pulled a disc from the player, spit on it, put it back, and everybody was amazed at the fact that it played perfectly.
What side did he spit on?
I doubt a lens covered in lung butter would be able to achieve focus.
* 10mm. It was the first thing they negotiated and it was the easiest thing they could agree about.
Other anecdotes about the history of CD are easy to find on the Internet and a little less favorable about the negotiation process. For example, Philips had in mind to make the OUTSIDE diameter 11.5cm, to match the size of the cassette. That way, it would be easy to fit CD's and CD players into e.g. storage systems that were already available for cassettes. And Polygram (the record company that Philips owned) built a factory in Germany with machines to press 11.5cm discs. Sony didn't own a record company at the time, so they were worried that Philips would be at an advantage (and rightly so). So they insisted that the diameter be 12cm "so that the 9th symphony of Beethoven would fit". This cost Philips a lot of time and money. They even already had prototypes (Google for "Pinkeltje") and test discs.
Another anecdote: Philips already had the TDA1540 D/A converter which was 14 bits. But Sony insisted that the CD should use 16 bit audio. Philips didn't have time to develop another D/A converter for their first CD player so they had to invent 4x oversampling and put it in their first CD players.
Sony originally wanted 44056 samples per second, and Philips wanted 44000 I think (my memory is vague but this story is on the Internet somewhere). They settled on 44100 because it was a convenient multiple of the number of lines in an NTSC as well as a PAL video signal. When Philips and Sony started working together on the CD standard, Sony already had a device to record digital audio on a U-Matic video tape.
In the late 1990s I talked to a colleague at Philips Hearing Instruments who had been involved in the development of the CD (he gave me a pre-production Philips CD-100 which I still own and which still works), and he told me some hairy stories about how Philips really did all the development work and Sony just paid for the research and regularly caused massive pains to the development team because they changed stuff that everyone at Philips thought they had already agreed on. I wouldn't be surprised if this was the reason that Sony beat Philips to market with the first CD players. But I also remember that the first Sony CD players weren't that good: they had a standard DC motor with a worm drive to move the laser and it wasn't as fast and accurate as the Philips mechanisms which were based on a linear motor. Nowadays of course all CD mechanisms have worm drives because motors, lubrication, machining accuracy and magnets have improved over the years.
Jac Goudsmit The standard was always 16-bit audio, early 12 and 14-bit DACs simply discarded the extra low-order bits (an absolutely trivial thing to implement in digital logic) simply because it was not practical at the time to implement the logic to utilize those extra bits in a manner that brought you above the inherent noise floor (most people do not realize how low a noise floor you need to actually exploit a 16-bit ADC or DAC).
But then most of the anecdotes surrounding the early CD development have been disproven over the years, including the often claimed Beethoven Symphony as the size of CD required to accommodate 74 minutes of music could not have been determined until after the encoding format was defined and the encoding format had not yet been defined at the time that story claims to have occurred (in fact, there were proposals to use encoding formats that would have allowed up to 97 minutes on a 10cm disc also being considered)...too much about the standard had yet to be pinned down at that time even though engineering proofs of concept likely existed since they would need to validate the basic hardware requirements and limits...pinning down modulation and error correction schemes would have logically occurred after the basic hardware premise had been tested.
I remember a CD which was scratched so bad no CD players in our house could play the entire disc. I wowed when the car stereo managed to play the CD just fine.
Car stereo's have skip protection memory buffers and spin the CD at a much higher speed.
Neither helps recover data from a scratched disc. Car stereos are just often built like tanks.
I had a CD-R that I burned in Disc-at-Once (single session) mode on an old burner that only supported Track-at-Once mode. I'm not sure how that ancient version of Easy CD Creator allowed this to happen, but it completed the burn successfully.
Every CD player I had could play the first couple tracks, and if I played straight through, they would go well into the third. But then they would hang and eventually throw an error.
But one particular Sony Discman could read the entire disc just fine. I think I later found a PC DVD drive that could also do it. Probably just very forgiving firmware.
I used to rip scratched CDs on my computer and then re-burn them onto another disc.
@@soulagent79 I still do
I watched a TV show many years ago that had a CD with 8 slots cut into it from the centre towards the edge. You would have though the CD was unplayable and yet it never missed a sound. It sounded as good as an intact version of the same disc.
I just want to say that I'm watching this in 2021 with a brand new BluRay drive in my PC that has now only been used to burn CDs. What a time to be alive.
ah a '2 minute papers' fan
The CD has been the best media for music imo. Its small enough not to be inconvenient like laserdisc or vinyl, while large enough for proper album art/sleeve to fit with the case. Capacity/quality ratio perfect for a single album of music. Its both hi-tech and old-school simultaneously. When you own an official CD of your fav band/artist, youre connected with them in a way. Theres some old-school shenanigans to be had in the whole process of taking a CD out of the case and popping it into the car audio while exploring the album art and then enjoying the ride to your fav music.
you forget to mention its lossless
Agreed, I'm glad you can still get a new Subaru with a CD player.
A single-disc, optional add-on, just like in 1998 haha.
(But in the center console)
This was super fun to watch! My mom, brother, and I have all worked with CD/DVD manufacturing, so it was nice seeing someone else appreciate how they're made and the process to do it.
Fun fact, this video in 4K is 1.67GB, about 2.5 CD-ROMs worth of content. Which we just went through in about 17 minutes. Not bad :)
That's roughly 1.6MB/s. (Mode 1) CD-ROMs are around 150kB/s.
Streaming in 4K amounts to the data of ten CD-Players playing simultaneously.
In other words, 4K requires just a quarter .wav
That means this video can be put on a dvd
How large would it be if it was a RealMedia file?
@@chitlitlah Most likely around double the size; as the RealVideo codec isn’t as efficient as the H.265/HEVC and VP9/AV1 (which is what UA-cam uses) codecs commonly used for 4K video.
What I love about this channel is how in depth you take everything. There are things that I've always wondered "but how?" You explain it all, right up to the point where I'd almost need an engineering degree to truly understand it lol.
I fell in love with the compact disc format in the '80s. Well mastered releases can sound amazingly faithful and vastly more so than phonograph records. It does wonders for classical and jazz too!
Fully agree. The day I heard my first CD, I knew that my large vinyl collection was history. I've never looked back.
If you have tube amps and high quality speakers as well as a high quality turn table (all analog) and the vinyl is a good press, the first time you play the record the sound will be (theoretically) perfect
You need high quality amps tube or not. You’ll actually have a higher noise floor with the vinyl than with the CD. But I do appreciate a good vinyl album
As an electrical engineer, you have no idea how happy this video makes me. It's so well explained, and you reference deeper concepts in just the right way that I understand where you're going.
Awesome video!
I love the Dirty Harry reference you squeezed in there, nicely done
oh....do ya punk
Where was the reference? Hey, I gots to know.
lol vaguely racist...and a classic
I thougt I was the only one who noticed it ^^
Nothing racist about it.
THIS IS IT! I FOUND IT! The first video with the Jazz at the credits!
I started rewatching from his first video to now for the same moment 😂
I have had a stuttering problem my entire life. I always think it's only me, conveniently forgetting that most of the time I speak fine. When I see the outtakes from creators like the one at the end of your video posted today, it really helps me to feel better. Your delivery makes your videos enjoyable. Thanks for making these videos.
You’re literally answering every single one of the crazy questions I had as a child. People looked at me like I had lost my mind. Glad to see all of your content on UA-cam, it’s definitely much appreciated and brings me back in time.
The surprise Dirty Harry reference played without winks or nods was very well executed, I love this presentation style
Why can I only like this once! A fascinating subject, with your perfect balance between technical details and not overwhelming us, and a great sense of humour.
All these years and I’ve NEVER placed a cassette on top of a CD. On my to do list for this weekend.
Joe Rico my to do list is to take a cup and place it on the table. Never done that before.
ua-cam.com/video/LFrdqQZ8FFc/v-deo.html
@@pyeltd.5457😂 lol
In this context 2s complement is best thought of as a representation rather than the operation. It just makes basic operations like addition easier at the binary level. You can just add -6 and +8 in 2s complement binary representation and get the right sign in the result (also in 2s complement)
For audio, I think 2s complement has some additional benefits not mentioned. In addition to addition, it makes multiplication easier, which makes it easier to add gain digitally and it has a single 0-value
The dude just finished with an excellent description of NRZI and then says that 2s complement makes his brain hurt, lol. He's nothing if not modest.
Yep, it's the easiest way to manipulate signed data because it acts exactly like unsigned data that's been shifted by half of the available range. In other words, unsigned audio would have it's silent point at a middle value and signed audio shifts it down to 0. But if we subtract 1, we wrap around to FFFF (65535) so making that represent -1 means signed and unsigned math can use the same binary functions. We just need to know that our overflow (and hopefully clipping) point is now 7FFF in the positive direction and 8000 in the negative.
I love CDs, somehow owning a physical copy of the music I love makes me feel better than just streaming it. But I never really understood how binary code is translated into sound? That’s pure magic right there.
whatever device you wrote that comment on is literally just running all on binary code..
And there good for piracy
@etchatails the ease of piracy is actually why i don't care for CDs as a physical medium. Anyone can burn a CD, and to me it makes them less interesting. Bootlegging vinyl on the other hand, requires highly specialized equipment and i imagine if that technology becomes affordable and compact enough for the average music aficionado to acquire, vinyl will fall back out of favor. Easily reproducible media just doesn't feel as legitimate or collectible.
@GeebusCrust ehh. I see your point however bootlegging cds doesnt feel the same to me. For one buying the CD officially gives you the cd slip and usually a printed cd with nice art. That matters to me, i hate the look of blank cds with titles written on them in sharpie. So it is easy to pirate CDs but the art on the slip and the disc itself motivates me to buy from official sources and serves as a point that enhances the music for me (IMO).
I suppose someone with a printer that does CD printing could just print the art onto the blank CD but alot of cd slips I have contain such personal touches from the musicians that it adds to the experience for me.
A total aside but when I was helping a young friend write their first university essays I actually loaded up Wikipedia. They instantly said you can't use that, the Prof was clear on that. Then I showed her my dirty secret. The Reference section. If the information you want is there and it is cited you can use the source and the source will usually have much more information than Wikipedia. She thought that was amazing. I then took her to a reference library and helped her work through that. She had gone to a High School in another country that was primarily artistic so essay's weren't really a thing like they are here.
She was going to an Arts School for university but still had to take humanities. When she handed her first essay in her prof saw the physical books mentioned in the Bibliography and asked her why she didn't just use the internet. I don't have much faith in that school...
The rest of this video is fascinating.
I usually did this, and Google Scholar/Books, and our university's online library look-up system. I initially search Wikipedia for relevant sources, then Google Books/Scholar, and cross-reference if that publication is available in our uni library.
My fellow students and some professors were always confounded how I read or found these sources as if I read through the whole uni library knowing everything. My professors were more fond of physical sources that could be found in the library.
Since Google books also didnt show the whole book, I also read the entire relevant chapter(s) if it was available in our library. This gave me more sources available than what I can gather online and looks much more credible too. Took a bit more work but it really paid off and is much more efficient than just poring though the library randomly searching that even metadata doesn't help as much.
Hi Alec,
Coming from a Computer/ Communications / Engineering background, I read about these technologies as they were introduced to the world. It still fascinates me that there is so much attached to these formats by way of belt and braces /belt and suspenders technology.
Unless very interested in it, the last 15 years have seen people ignore the ‘magic’ behind the technology, preferring to accept that the stuff in the box works.
Thank you for deconstructing the myths and legends behind this everyday technology!
EXCELLENT video!
In the 1990s, I worked at a company that made CD-i productions and I'm pretty familiar with all the stuff that you mention in the video. When I started watching, I thought I was going to have to point out a bunch of mistakes but I was pleasantly surprised! I have nothing to add to the video; you even got Kees Schouhamer Immink's name almost right (his first name is pronounced "Case") :-)
The CD was a marvel at the time - and the audio quality is still the gold standard for listening experience in stereo - simply cause it is 'good enough' for all human ears. But we moved on and now with flash-storage got a medium that is not as long lasting, but far more convenient.
Longevity is largely dependent on the original quality of the media. I've got twenty year old N64 carts that still have games saved on the flash memory, while there are Saturn games of similar vintage that are succumbing to disc rot.
ThetaReactor
No, i am talking about the limited lifetime of data saved on flash memory. N64 cartridges got a battery to keep the savegames. If that runs out the data is lost.
In SD-Cards the data is stored in the form of charging the gate of the mosfets and those too will slowly discharge.
They both have a rather short limited lifetime even under good conditions.
A CD on the other hand will last for many decades when stored correctly. But under the "right" conditions can be dead within a few years even.
Most people also forget or don't know the fact that a computer's Solid State Drive is very similar to a flash SD card like is used in phones and cameras. They are all limited in life in some way. SSDs don't have to worry about any sort of charge in the way the old console memory cards did, nor like the SD cards - They're limited based on write cycles. Ever look at the warranty info for a Samsung SSD? "5 Years or 75TBW" They are saying it'll last AT LEAST 5 years or UP TO 75 Terabytes Written. Once you hit the TBW threshold, your drive is soon to give way. SSDs that fail prematurely are simply faulted due to some sort of defect. (840 Evo SSD in my gaming rig, 4 years and still going strong at just under 20 TBW)
But that ^ Up there sure explains why some of my SD cards have been totally dead after a long period of time of not being used
@@morgfarm1
The Nintendo 64 kept save game data in a replaceable memory expansion pack. I believe you meant to refer to Gameboy cartridges which were forced to tie data to the remaining lifetime of the button cell. Later versions were upgraded with writable flash memory. though
@@net28573 I could well be wrong, but I do remember the 3V button cell in the old cards. Flash drives that we see today still can fail to a loss of internal charge if left unused for too long is what I understood on another topic. That would explain the 4 dead SD cards I have that weren't used much. Though more recently my SD cards have failed by reaching the written data limit. How much that was im not sure but it was in a dash cam for about 8 months before it croaked
The stack of blank CD-R's in my basement are cheaper than a better FM transmitter, so I still use CDs for playing music in my car since it's only got radio and the wonderful 6-disc CD player integrated. It works well, and it's honestly really convenient since I don't have much songs
I love my CDs. You're going to be very hard pressed to find a similar or better quality digital copy of music without ripping straight off the CD, at least legally. Not only that, but the liner notes and photos gives you so much material, as opposed to digital files, which could be deleted on a whim.
Personally i just want uncompressed audio. Streaming is all lossy compressed. I usually create carefully done FLAC rips of my CDs and add id3 tags to it, including album artwork. The best of both worlds. The album being available as lossless files but also as physical copy in the collection that you can touch and hold in your hands.
There were a lot of optical media formats that tried to have higher quality audio than CD (the ones I can think of off the top of my head are SA-CD, DVD Audio, and Blu-ray Audio), but unfortunately none of them ever caught on.
@@Spearca good point! I have some amazing sounding CDs to the point that it's hard to imagine them sounding any better to the human ear.
@@AskDrannik The DSD codec itself (SACD) kinda did catch on though, you can either stream or download DSD audio streams or files currently, and even higher-res variants of DSD than DSD64 (SACD-quality) are a thing in the form of said streams or files.
@@KRAFTWERK2K6 I still buy my music on CD as well, streaming just isn't the same.
CD's were one of those "You had to Be There in the 80's" things to really appreciate what a breakthrough the format was. We have several generations that grew up with CDs and Mp3's that take it for granted. I remember seeing a few Dualdiscs in the mid 2000's but never bought one. I heard stories of Dual Discs getting stuck in slot loading car players, and some CD changers couldn't play them because they were too thick to load.
Until the late 1990s, most people had cassette players and not CD players.
You're my favourite old tech channel. Regards from Buenos Aires!
I have always loved history of modern items. This is pretty deep and informative. I am glad you are putting these videos together. Keep em coming.
This is amazing. Sometimes, in order to see how far we've come, we have to look back at where we've been. High capacity micro-sd cards never cease to blow my mind. May as well be alien technology compared to what we used 20 years ago to store data.
I like all the video examples they show in this channel: they are always sleek, attractive and originals.
Also the content of the video is top notch in term of meaning and how is constructed the explanation, a really great job.
Thanks a lot for your great work.
A-ha! I knew of Non-return-to-zero from my comp engineering college days but somehow didn't know it was implemented in CDs.
Same :)
I learned adout NRZI when reading USB spec lol
As a technology, I still find the compact disc a marvel of ingenuity, largely because the way information is stored on it. And the players used to convert that information via a laser pick up, into almost perfectly reproduced sound.
It certainly did revolutionise the way we listen to music.
And I am even more astounded by Mini Disc, that also allows the user to record, and re-record music on a disc that is half the size of a CD, yet with recorders equipped with a long play/record facility, you can store four CD's worth of music, on a tiny pocket sized disc. And don't get me started on Hi MD players, that take the medium even further. Truly amazing stuff, and amazing ideas.
I would like to know in a future video what are the differences between an original molded CD, a blank CD-R (with the process of writting data to it by a CD-Burner), and a CD-RW wrighting process which enables the rewriting of data on the same disc, and why not all CD drives are capable in reading the CD-RW properly. Thank you and cheers from Romania.
I think this is definitely headed toward burning and rewritables and I harbor great anticipation
CD-R uses organic dyes that can have the reflectivity changed with laser heating. CD-RW uses tellurium suboxide that somehow can change states of reflectivity with laser heating.
AutogolazzoJr
Forgive me if I'm being a pain in the ass, but....
Do you happen to know anything about CD+RW in this context?
I don't know what the materials are called but CD-RW is based on heating up the material in such a way that it either crystallizes or not. The crystals have a different reflection or refraction and if the reader is properly designed, it will see the difference. CD-RW is not compatible with the original specs for CD players, so CD players that predate CD-RW won't play them.
Jac Goudsmit In many respects CD-RW functions much like LCD, the difference being that one changes the crystal state electrically (to rotate the crystal) and the other uses differing levels of heat to change crystal state semi-permanently.
As for the main reason that many older CD players could not read CD-Rs, it typically came down to beam intensity. The typical CD-R dyes were usually pretty dark and so you needed a much more powerful laser beam to actually transmit enough light into the disc in order to get an adequate amount of light back out of the disc due to the very lossy transmission medium. Early CD players were designed for the highly reflective pressed CDs and their intensity was often intentionally turned down to help extend the life of their lasers. The lifespan of a laser diode is directly related to how hard you drive the laser and early laser diodes were both less efficient and not nearly as reliable long term, but especially if driven at higher than necessary power levels...and a CD player would be expected to provide many thousands of hours of life during its operational life. In fact, this is what held back Blu-Ray/HD-DVD development by up to a decade while they waited for a blue laser diode that could deliver enough hours of life to be a practical home entertainment/storage device (without needing its laser replaced every few movies/discs) - the main players recognized what a blue laser could mean in terms of increased data storage capacity the instant the blue LED, then laser, were invented, as it was the wavelength of the laser that limited data and track density on a CD, but they could not implement a consumer product that exploited that capability until blue laser diode operational life could be sufficiently extended.
Before I say anything else, I just have to compliment you and say that you seem really comfortable with these recent videos and I love the subtle and not-so-subtle jokes peppered into your scripts.
I was glad to hear you get into the corrective elements of the compact disc, as it's one of the most impressive and interesting elements to the design of CDs in my eyes. They saw an inevitable problem and they engineered ingenious solutions.
I like CDs. I always like having some kind of physical copy of my music.
Yeah I like to have physical stuff
I never want to use clouds and stuff like that
Physical media #1
Either CD or Record for me
AetheralMeowstic same
The good thing is, if you are limited on space, you can streamline your CD/DVD collection to be as specific as you like cheaply. Then "everything else" can be left to streaming services. Eventually you have shelves full of special editions and limited versions and releases that have not or will never appear on a streaming service.
Man, I must be getting old. I remember lots of the "vintage" technology you discuss back when it was new. VHS? Yup. Laserdisk? Yeah. CD? Yes. I had an 8-track player in my bedroom, and I remember listening to Sonny & Cher, the Grateful Dead, KISS, Deep Purple, etc. My Dad had an 8-track player, and a CB radio, in his '73 El Camino. I remember the switch from 8-tracks to cassette tapes...so yeah, I'm THAT old...LoL
I have heard from people who were working with Philips at the time that one of the primary things Sony brought to the table was the actual manufacturing process. Not just a size change to slow Philips down, but the idea of pressing the lands into the plastic layer itself. Thus negating the possibility of Disc Rot, something that Sony engineers had feared would happen with sloppy manufacturing processes. Turns out they made a good move with that, as you have already covered the horrors of Disc Rot previously.
While less susceptible to disc rot than Laserdiscs, CD's aren't completely immune. No doubt the varnish coating and a single-sided disc is cleaner and less prone to issues than the glued-together Laserdisc, but there are cases where CDs have been destroyed from rot, often by a fungus that likes to eat aluminum iirc.
That said, it certainly is a better design I think. Though humorously the DVD is constructed rather like a Laserdisc, even on single sided discs. With some DVDs being around for more than 20 years (and still working, I presume) it seems to me that the Laserdisc's rot-prone reputation was always due to sloppy manufacturing. I'd hazard a guess that the non-digital nature of LD made people more careless around it, and the stringent clean-room conditions required by CDs and DVDs weren't followed.
And, just to press your buttons a bit, keep in mind that *the worst* Laserdisc manufacturing plant for rotting discs was run by Sony!
Technology Connections I've never encountered disc rot in my life, and I have CDs in my library that were pressed as far back as 1987. All CDs still play just fine, no skipping at all. The only skipping I encountered is from burned CD-Rs.
I always assumed disc rot was a myth. I think it's just very rare.
It's just as well Sony DID get on board. If it were left to Philips alone, Ugh! What a gosh-awful mess the CD would've been. For this reason, I give ALL the credit for creating the CD format exclusively to SONY!
DVD is constructed exactly like two CDs glued back to back to each other - the pits are moulded into the outer plastic layer that is then mirror-coated. Except half as thick. If the resin holding together the halves is any good, it stands absolutely to reason that DVDs would last as well as CDs and then some.
CD-Rs of olde were terribly plagued with disc rot, I remember very well the pirate (oops) "BACKUPS" of early 2000s would go bad by mid 2000s. Never seen it with pressed discs tho indeed.
I've never seen such a positive comments section with so many smart people. I just started watching this channel a few days ago but I'm blown away by the knowledge and friendliness flying around here. I am learning so much about things I never even cared to question so thank you for these amazing videos and inspiring in me a desire for more knowledge.
“And then we’ll relish in the fact that everything is on the internet now”; that with the vinyl jab had me rolling. Extra disgruntled in this one?! Ha ha
Speaking of audio quality, Alec: I have some constructive feedback (pardon the pun), if your workflow supports it:
The placement of your mic works quite well for maintaining consistent volume, but the proximity to your chest means the 200-800Hz range of your voice is about 10 decibels louder than the rest, which makes you sound muffled in comparison to other UA-cam creators. May I suggest that you cut that range by 6-7dB before you normalize the audio level on your next video? This will greatly improve intelligibility at lower volumes, at the cost of raising the noise floor slightly.
Always appreciate your videos, by the way. They're always clear, well thought out, and entertaining. Keep doing what you love!
h
how do you hear these details
@@milkywaydotmoe some people have really well tuned headphones or sound monitors
@@milkywaydotmoe mixing a lot of audio can help you develop a sense for frequency ranges
Another great video! I find it fascinating that the actual data is encoded in the plastic, not the aluminum. As for the CD being obsolete I would beg to differ. There really isn't a decent mainstream way to purchase fully lossless audio today. Sadly I don't think the demand is really there for it. The younger generation today doesn't really understand the difference, and seem to be content listening to compressed audio through earbuds. I grew up in the era of big speakers and amplifiers, and the birth of the CD. To this day I still enjoy playing my CDs on a real stereo system. That will never be obsolete to me.
I totally agree with everything you said there, and yes how young people now are happy to listen to their music on a tiny mobile phone speaker!
And don't even get me started on the sound quality of DAB radio!
The sad reality is that I know
some kids that do not know what a CD is...
It may help to understand that the aluminum layer is vapor deposited (an *extremely* thin layer) onto the plastic CD disc after pressing - so, in a sense, both the plastic disc and the aluminum carry the information as the aluminum is simply applied to the surface of the plastic in order to provide the optical reflectivity that the player needs to effectively see the encoded data in an efficient manner. As such, both the plastic disc and the aluminum reflective layer reproduce the lands and pits, it’s just much easier to bounce light off the highly reflective aluminum layer.
It really bothers me how the industry essentially leapfrogged to streaming before implementing a mainstream and popular way to download proper lossless... sure, some sites offer it, but they are not the big places the general public would necessarily think of to go to download music, and the number of sites can be counted on 2 hands. Now that they’ve marketed actually downloading anything as unfashionable and the old way of doing things, nobody even cares anymore. It’s disgusting.
I don't want to say this is a bunch of boomers gathering to bitch a bit, but yeah, it's kinda like that in this comments section
I'm a newcomer to this channel and I'm loving the content. So informative! Great job.
Just take those old CD's off the shelf
I'll sit and listen to them by myself
Today's music been compressed to shit
I like my old time Compact Disc
*Anona Mouse:* Very well said. Additionally, downloadable media is sometimes subject to contract and litigation. That mp3 might be yours to keep because you paid for it, but if you need to restore that data and you can't because someone had an argument with Amazon or iTunes, or a country, you're out of luck. Provided that the CD (or any physical format) hasn't been degraded, you will always have access to it. EDIT: Or the player that reads it.
@@Christopher-N All my CD's got transferred to my SSD via EAC (Image copy). I used Audacity to divy up the single track into songs, and Flac to compress the finished product. Then I made backups. Now I am immune to CD rot and CD player failure.
SMH at the fact that vinyl is making a comeback. They should bring back wire recorders while they're at it.
@@Dynamic_Editor Dynamic range. The loudness war left many casualties behind.
I'm also no fan of craptastic MP3's. With storage and bandwidth as cheap as they are, the worst we should be encoding are highest bitrate VBR MP3 while FLAC should be the default.
@@Dynamic_Editor I'll have to look into Perfect Declipper. Thanks for that info.
lifehack no. 44100: F L A C.
no need to thank me
Andreas Vollenweider! Ah, this brings back memories of artists like Don Dorsey, Patrick Moraz, Michael Hoenig, Craig Anderton, the Nightingale collection, etc. My dad is an audiophile and had tons of the Telarc and CBS collection samplers.
Synthesizer music reproduced in pure digital and played on Klipsch speakers was absolutely magic in the 80's. Most CDs back then had a designation "DDD" which meant the pipeline was all digital from the synth directly to the recording computer. No line noise at all, bright treble, and no evil "bass boost" to be found. Such a great privilege to be alive when all this tech was brand new!
Did I ever mention how much I love your channel? Cheers!
Thanks for this excellent video.. I'm suddenly in awe of my old forgotten CDs languishing somewhere in a dusty corner of my house
This channel is everything I wanted in life. Someone who explains these things with all the unneeded nerdiness and pedantry.
Be careful when throwing the word "obsolete" around. Passive media is never obsolete as long as there is a machine to extract information from it and someone who is interested in said information. :)
yeah but DVDs are way more reliable. CD-Rot is very common, while not so much on dvds. Still, i wish there was a cheap consumer data tape alternative which could at least do 50GB. DVDs are too small and not cheap enough to justify not buying another hdds for archiving. And blurays are just too expensive and no one has them.
There used to be a lot of consumer data tape alternatives. I've used them to archive projects from my A/V workstation back in the day. Going back to something I archived 20 years ago is a crapshoot. Sometimes I'm successful and sometimes I'm not. A lot can happen to the bits stored on those tapes over time.
Not to mention as long as new compact discs continue to be made. It's not like compact cassette where, although you can technically still buy a new deck, it's going to be crap because the dolby noise reduction technology is no longer being licensed to them.
CD rot is insanely rare and apart from that one plant producing bad pressings for a couple of years, so it's barely even worth taking into account.
Honestly, the biggest strike against compact disc is the loudness war, and that's a whole another topic entirely - one that wouldn't make a bad subject of a video in itself, really. There's a lot of misconceptions regarding the quality of CD vs vinyl that really need to be set straight.
Tetsuron The Loudness war is a mixing and mastering issue, not a format issue
That is correct - but it has certainly contributed to the poor perception of the format against vinyl among wannabe audiophiles.
5:32 I love this part of the video! I watch this video all the time, and it's this Dirty Harry reference that makes me remember that I've watched this already, many times. Your explanations are very easy to understand btw!
8:43 yep, that's how I was able to do a lot of my research in highschool. Can't cite wikipedia but can cite the citations for wikipedia.
Two's complement shouldn't hurt your brain. To encode the negative of a number, invert the bits of its positive value representation (this is one's complement), then add 1 to the resulting binary value (this is two's complement). Decoding works the same way, first invert all bits, then add 1. The add one is to avoid having an encoding for negative zero (note that some other encodings do allow for negative zero for various reasons), and overflowing then also is 'natural' (zero to maximum positive, then minimum negative to -1, and then zero again).
Thanks, good explanation!
The reason to use it, is that in the microprocesors , you can add and substract with the same digital component, that is an adder. The adder can add or substract , just because it's an adder that can take a negative number as an argument. The circuit becomes super simple and makes no distinction with any number , negative nor positive.
@@intron9 Yep, that's the 'natural overflow' part. The increment/decrement/add/subtract operations do not need to know if it's an unsigned or signed value that they are operating on.
A trick to get the maximum unsigned value of a given sized type in languages like C (apart from using macros like UINT_MAX) is to cast -1 to unsigned, since unsigned zero "underflows" to the maximum unsigned value when decremented and this is the same binary representation as -1. Also, incrementing negative values does the right thing (which would not be the case if the most significant bit would be interpreted as sign and the rest of the bits just the positive value representation).
Also note that this is the reason why the negative numbers can represent one more value (e.g. signed byte is -128..+127), since zero (0) is part of the positive numbers (128 values: 0..+127), but the negative numbers do not need to represent zero (128 values: -128..-1). Same applies to 16-bit, 32-bit, ... integer representations similarly.
I like to think of the principle like a mechanical car odometer or tape counter: If you go backwards from 000, it rolls over to 999 and goes backward. 995 is equivalent to -5, 990 to -10, and so forth. This is the decimal equivalent of the same principle, called nines' complement.
Subtraction with nines' complement arithmetic works the same way in decimal as with twos' complement in binary. Many mechanical adding machines (used back before electronic calculators became affordable) used this to allow calculating subtractions even with a mechanism that could natively only add. To compute a difference, you could simply add the nine's complement of the number to be subtracted, then add 1.
(As a side note, I find the naming oddly inconsistent. Logically it should be either ones' complement and nines' complement, or twos' complement and tens' complement, but not twos' complement and nines' complement. Oh well.)
you should do a run of your videos on DVD. I would buy the box set.
Agreed lots of info and history on electronics .
We could have each series as a box set, the CD series, the LaserDisc series, interactive menus, deleted scenes, all that cool DVD stuff
I really really enjoy your videos. They are educational, informative, yet still light hearted and funny. I love the bloopers at the end, they show a humble guy just having fun with his UA-cam channel. Keep it up. I'm Patreon'ing you cuz you are just so likable and geeky and fun.
Always love your videos! The bloopers at the end here were really nice.
I knew a lot of this, but it's still really awesome to have you explain it as you do. It's like you fill in the pits in my own brain with useful information. Wait, would that blank out my mind? WHAT ARE YOU DOING?! Seriously though, good video! Also I wanted to give props for saving your "like and subscribe" for the end of the video. I don't think enough people express gratitude for doing that. I've been subscribed for a while, but look for me soon on your Patreon page. :)
5:54 Sufjan Stevens' Illinois! So pleasantly surprised to see this. One of my favorite albums of all time!
Physical media, undesirable? Unlike with streaming, you keep it after you pay for it, and the copyright holders can't revoke your access to it. Physical media, while sometimes bulky and subjectively inconvenient, is objectively better.
Gotta love first owner rights, when I'm tired of the disc I can at least sell it
Not really bulky if you put them in a disc binder and toss the cases.
I think the bulkiness adds to its appeal. There are a lot of people who prefer bulkier books to their digital equivalent to showcase how much they're reading. It's almost a status symbol.
I plan to acquire more physical media in the future since there's not much difference in price (often the physical being the cheaper option thanks to lobbying) simply to show off them. I might even invest in either an internal or USB Blu-ray drive, I still keeping my DVD-burner in my PC since it doesn't impact anything but I still have a lot of CDs and DVDs. I plan to publish my games on CD or DVD, and since my engine is so space efficient (and will be even more so once I finish porting the compression algorithms to D) I might use the 80mm CDs or DVDs for their retro-futuristic feel (I still have a very rare 80mm CD-RW, my favorite disc).
Very true. I still make a point of buying CDs, and then ripping them for convenience and portability. But I still have the physical media, unlike an iTunes download.
CDs also can't be suddenly removed from your collection because a contract was up. And they still work if your Internet goes out.
Edit: Oh, and they're not at risk of getting corrupted like other writable media is.
Great video! I wish you had more "connections" between techs like James Burke did with history with his show. I hope you cover more on error correction. It's amazing LDPC and turbo codes are used in consumer applications these days.
I just realized the, ahem, connection with Burke’s “Connections” series. Thanks for pointing it out.
The Compact Disc, truly a technological marvel. And a visionary format.
Amazing videos, truly a treasure on UA-cam! Also, I still go to a used CD store and rip my own CDs to flac files rather than buying my music online...partially for quality (compared to mp3s) but also partially money. So yeah 🤷
Protection of the file is what CD is all about.Without the protection the sound quality will degrade over time.The only way to protect a flac file is to burn it to an M disc.
@@fraudsarentfriends4717 How can the sound quality of a flac (a lossless format) degrade over time? Or you worry about degradation happening in an hard disk?
The Compact disc is the evolution of the Audio Long Play project. a group started by Phillips engineers in 1974 to develop an audio counterpart to the Video Long Play project AKA LaserDisc. As it turns out, using optical discs to store analog audio better than the human ear is crazy difficult. So they made the decision at the end of 1975 to switch to a digital format with error correction, which they developed over the next few 3 years into the Compact disc. On March 8th 1979, this format was shown to an audience of uninterested Japanese executives. That is, except for one group of executives from Sony, who were working on their own digital audio disc. Together they would refine the Compact disc over the next year, finally bringing it to market in late 1982
As someone who has been repairing speakers for years, setting up countless sound systems and building my reference system over the years, I can confidently say that CDs are superior to records.
Everyone who is hasn't been fooled by vinyl sales people will agree with you.
@@schragemusik what? Your sentence structure is confusing, I have no idea what you mean honestly.
@@americanidle1277 sorry. Wrote on a phone without my glasses on. An extraneous ‘is’ there. I was wholeheartedly agreeing with you.
@@schragemusik oh that makes sense. Haha long live CD. Now the part you may disagree with is my preference for upmixing 2 channel music. I use DTS Neo X primarily but I also have had good results with Logic 7, THX Neural and Dolby Pro Logic 2X. These don't steer instruments around the room (which is unrealistic), they extract the reverberations, reflections and ambience present within the original recording and place them to the sides and back of the room where they belong. It's very enveloping and not gimmicky.
Really. I have a pair of speakers form either the late 1970's to early 80's that need new woofers
Down the wormhole of Tech Connect videos I go again.
By the end of the quarantine, I would have watched all of your content, plus TechCon2's stuff...
Which is only a good thing, because this content is so good.
Living near Eindhoven (aka the place where philips started) I heard a lot of stories from people who worked on different philips projects. Last month I talked with someone who worked on the cd-i.
Growing up in the early 00's I learned how cd's work at the age of 8 (simplified).
A great video, looking forward to the rest of the series on the wonders of the CD. It was very interesting the whole encoding/decoding & error correction methods used by CD players and what's done even before it's sent to the CD players DAC, those people at Philips and Sony who designed the CD were some smart cookies! Especially for 1980's computer technology!
As always, a fantastic and well-written video!
This is your best video that I've seen. On every level. period. Thank you! Please keep up the good work, I really enjoy your insights, sarcastic comments, and dry humor :)
I'm really looking forward to the CR-R and CD-RW explanation but also the explanation of CD+R and CD+RW
You're confusing it with DVD-R/RW vs DVD+R/RW
There were never “CD+R/RW” formats. You’re thinking of DVD+R/RW.
Lawrence D’Oliveiro yes you’re right, I’m just remembering there being a lot and always getting disks that didn’t work.
Alexagrigorieff hopefully we’ll get a video on them too
ROM (read only) / R (record only once) / RW (rewrite able)
Compact Disc were less splintered than DVD, no bullshit '+' or '-' back then.
Thank you so much for your video , I couldn’t believe that one day I have to show it to my child because he doesn’t know how CD used to work. There was a question on it in his homework. Thank you 🙏
I have a hard time accepting that Compact Disks are obsolete. I use them semi frequently at home (mostly for retro computing). Many of my computer gaming buddies simply don't have a optical disk drive in their gaming PC's. I could not fathom being without an optical disk drive. As you said, they were (and still are) an amazing piece of technology.
I mean, they have their uses, but in the grand scheme they're next to dead. Most high-end laptops are abandoning them. CD players are increasingly rare in cars. And aside from their utility, 700 megabytes is just nothing these days.
I wish it wasn't dying as an audio distribution format, but unless they get a retro resurgence like Vinyl and Cassettes have (which you never know, they might) I'm thinking they'll just sort of teeter on the edge of darkness.
I think of Blu ray as a spiritual successor, and is a cost effective way of distributing very large quantities of data, such as high resolution films. Although I expect even Blu ray will die off once broadband technology to every home is reliably over say 50-60Mbps. We're nearly there in some places, just not quite.
(edit out redundant text)
Key operative phrase "retro computing" not so much audio. Disks, with the physical technology i.e. moving parts just are not as fast nor as compact as USB and TransFlash with a whole terabyte of data, as Bullwinkle would say, "All on this itty bitty card", Hell I do so much with so many different formats, I got a USB floppy drive as well as an external CD/DVD/Blu-Ray drive My main stereo system is still analog in terms of the amp, sub and speakers. Nothing does bass like a bigass subwoofer or highs like an HF horn
CD's are still being released for music, though I suspect mostly for classical music these days. Pure CD only players are hard, if not impossible to find, about the same for DVD. However you can still buy BD players, and they are fully backward compatible with everything stamped onto a 5.25" optical disk (except for those CD-LD combos in that size).
I expressed that I have a hard time "accepting" there obsolescence. Not "believing".
You have explained something I have been wondering for years in such clear concise video, this is awesome!
Thank you so much
Unfortunately, the How It's Made episode is blocked in some countries. I was looking forward to seeing it :`(
Use a VPN to make it look like you are in the us
www.proxfree.com/youtube-proxy.php
ua-cam.com/video/ut_40U0t9pU/v-deo.html
On October 1, 1982, the first commercial compact disc, Billy Joel's "52nd Street," was released in Japan. We're almost 40 years from there =)
Props for the "Amazing Stories" inset video. Early CG at its best! :)
Gotta admire your dedication to matching up the run-time on the VCR with the video's run time at 14:54 when you say "and that's where we hit pause"
(OK so I think it's about half a second off but still...)
It's not a VCR, it is CD player
@@danek_hren oops
I still buy all my music on CD, guess I'm just a dinosaur.
I love CDs, I rip them to FLAC for use in my house and 256 kb for use in the car.
All my CDs are dumped on my NAS and the stereo in the kitchen and living room can pick it up.
You're not alone, physical media for me is not going away until it simply can't be found anymore.
As well as being an enjoyable listening experience physical media is retro and cool.
@@Dontcareaboutoffending Yep. I like to have a physical copy. So if my internet is out, I can still play it back. I'm on satellite internet where I live and it sucks.
@@jochenstacker7448 you mean 256 kbps *MP3* for your car?
I continue to be impressed with both your knowledge and your excellent sense of humor. Thanks for this video!!!
"But being this is a 120mm compact disc, the best audio format in the world and would blow your socks right off, you've gotta ask yourself one question: "Do I feel lucky?" Well, do ya, punk?"
Reference explainer squad, GET IN HERE!!
Yes, Fuad. That is very funny.
@@lordofthecats6397 dirty hairy said that when he didn't know if he had a bullet left In his gun while pointing it at a criminal.
You are one of the best UA-camrs I've ever discovered. Great conent, Sir! Greetings from Poland
Great Dirty Harry quote - that made my day.
It's mind boggling how people were able to create these complex technologies. I can barely understand it and I wouldn't say I'm stupid, but to conceive of these concepts such a long time ago takes some incredible intelligence.
Minor quibble: A hard disk containing files is also a continuous stream of bits. There's no practical difference between what a computer does to display audio CD tracks as files and what it does to display regular filesystem data as files, apart from not having a name stored. A simple disk filesystem also has the equivalent of a table of contents describing byte offsets at which to find file start positions as well as the lengths of each one.
Hard drives can come with multiple platters, so the data is not necessarily one continuous stream on a single platter. Table of content varies greatly with hard drive with distributed TOC with journaling like NTFS/EXT3+ vs simple local like CD/FATx.
Yeah, my first thought after hearing that is, "You just described a filesystem". It's a very simplified, OS 101 filesystem, but a filesystem nonetheless.
I think the point here is that Windows' "Track01.cda" is a logical construct that is completely virtualized. They aren't ".CDA" files on the disc, they're just ranges of raw samples.
Those old enough to remember MSCDEX days can tell you that an audio CD does not present a file system to the OS.
Although I suppose you could turn that around and say the the "file system" on CDDA discs just isn't supported by MSCDEX and DOS.
This all gets very theoretical at some point.
Not quite. Unlike a CD, the magnetic disk is not written as a single contiguous track. Each track is a closed loop. Then there are multiple heads, one per surface.
CDs were designed for audio first, and general data files (CD-ROM) later.
DVDs were designed to be a computer data format from the beginning, with a proper computer file system (actually two, ISO-9660 and UDF), with all the actual applications (DVD-Video, DVD-Audio etc) being done basically as file formats on top of that.
Great job spitting out that bit on two's complement. That was fun. Great job on simplifying the destructive interference thing as well. A little over simplified, but good enough for understanding.
And finally, your blurb on wikipedia research is SPOT ON. I started doing that almost as soon as wikipedia launched. I did the exact same thing, too, when someone "reminded" me I couldn't use wikipedia, I would just scroll to the bottom of the article and point.
Even after knowing how lasers work on CDs, I cannot believe they work.
Excellent video! I remember buying my first CD player in 1988. It creeped me out to have dead silence between songs because I was so used to tape hiss. I'm excited to see upcoming videos. VCD (or Video-CD) was very common in Taiwan around 1999 to 2001 (movies on two CD-ROMs). Taiwanese people weren't very interested in buying "players" for anything. I moved to Taiwan from Ohio in 1996 and I've only met one family who had a VHS player/recorder, and nobody had an answering machine. It wasn't until PC-compatible DVD drives became affordable/available that DVD really took off. (In 1998, I watched the first "Star Wars" movie on LaserDisc at a rich kid's house, which was actually my first LaserDisc experience.)
When you mentioned DualDisc my first thought was Strait Outta Lynwood
Same
Best video I've seen in a long time! Excellent work!
Anyone remember that rootkit controversy when Sony installed some software on the optical disc?
Philips piped up to add their penny's worth to state that because it didn't follow the red book standard (it had file data - the rootkit installer) it could not be labelled as 'Compact Disc Digital Audio.'
Yeah, i remember that and Philips were right, you cant just change things and not follow the standard, if you dont follow standards you cant know it is compatible and everything is thrown out the window. We would end up with products that might work sometimes and sometimes not, a CD player that cant play some CD´s, a certain car that wont start if it has fuel from a certain brand in the tank etc, it would be absolute tech hell.
It has nothing to do with breaking the red book standard, as far as I can tell. Here's some information on the topic: en.wikipedia.org/wiki/Sony_BMG_copy_protection_rootkit_scandal
lol - Sony addressed that optical disc controversy by _only_ adding rootkit software to _SOME_ of their movie DVDs.
@@xerzy It has. If the disc contains anything other than Compact Disc Digital Audio, it cannot use that logo as it breaks that particular standard. Sony/BMG *did* label it as a CDDA, including using the logo and was wrong to do so. Philips put in their comment to point out a fact.
I kept my computers set to do nothing when I insert a disk. That way I could check for it
The first CD I bought was Olivia Newton-John's Totally Hot. I remember being blown away by how much more treble it had than the cassette version. It convinced me to upgrade almost my entire music collection, AND put a CD player in the car! Fun times.
13:35 "this was a smart move" yeah except that most of us dumb kids thought the data was on the bottom so we left our disc's out, label side down.
Awesome research and explanation as always. You are the king of old media formats!
The pit depth noted may have been correct. Recall that the very first CD and videodisc players used Ali Javan's helium-neon gas laser operating at 632.8nm because the cheaper and simpler aluminum gallium arsenide laser diodes operating closer to 800nm were not yet available in quantity.
I do not believe any CD players use He-Ne lasers, except perhaps in the experimental stages. In any case the referenced wavelength in the document I found was something like 530 or 550nm, way way off from either the 780nm of solid state infrared or the 632.8nm of He-Ne.
Technology Connections A good technical article I came across while verifying my understanding of how the decoding is done (I always try to validate my understanding before replying to technical questions) on *The Physics of the Compact Disc*: leung.uwaterloo.ca/CHEM/750/Lectures%202007/Lect%20Mat/physics%20of%20cd%20pe930103.pdf
The wavelength 500 nm is correct, since that is the wavelength of the light in the polycarbonate medium. In vacuum or air the laser light’s wavelength is 780 nm; divide that by polycarbonate’s refractive index of 1.55 and you get about 500 nm. This also explains the pit depth of 120 nm, which is one-quarter of this. In effect, light is “compressed” or “squeezed” in a medium with high refractive index.
@@pmonta the laser wavelength doesn't change when it enters a medium with a different refractive index. That would violate conservation of energy. This is only possible with things like nonlinear crystals which do second harmonic generation by effectively summing two photons together. None of that happens in plastic.
@@Muonium1 The frequency doesn't change, so there's no change in energy, but the wavelength does change. The first section of Wikipedia's page on "refractive index" has some discussion.
I like the way CD's work, but I think that a good, clean, well pressed and mastered vinyl record, played on a good equipment sounds better than a CD in the same conditions.
Just love your channel, Alec!
"Use your imagination" for the "Big Hair" slide? Really? There's a billion Glam Rock/Metal (or Hair Band) images out there that easily got the point across. :)
Trouble was, very few were public domain and/or could be used with attribution. Plus, even if I found a suitable picture, some people would complain about whatever band I chose. So I just left it up to you.
Ahh, got it. Found some that would work, but they all sucked and didn't prove a point. :)
I'm surprised that something so ...err.....big..., isn't so easy to find without hurdles, and while anything copyrighted can be used under "Fair-Use", UA-cam is horrible at that, so yeah, upon research, your way was the way to go. (Curse ContentID!)
Being a connoisseur of porn from the 70s and 80s, Big Hair has completely different connotations.
Using your imagination is probably best.
Pretty much. Did you stop at any moment and consider he maybe wasn't talking about head hair...
In that case, true. :)
I'm coming from the hard disk industry and what impressed me most was the actuator arm being able to exactly position over each track. A respectable feat in a lab but to do it in a hand held portable inexpensive consumer product, wow.
There aren't any "tracks". It's one continuous spiral. There are two positioners, the coarse one (usually a stepper motor winding a screw) moves the cradle roughly under the target, and a voice coil within the cradle that finely positions the laser.
Hard disks are now up to 12 TB. That fact melts my brain every time I think about it.
6:35 please, you've already mentioned the Nyquist-Shannon Sampling Theorem. As long as you don't break into quaternions, I think we'll be fine ;)
Here in Mathland, quaternions break into you.
Congratulations .One of the best tech channels .
The difference between this and a normal disc is that this disc is compact.
It's so obvious, now that you've explained it.
The difference between a compact cassette and a CD is that the CD is a disc :-)
I only wish that these discs were digital and versatile, but I guess they wouldn't be able to make them compact if they added those features.
DysnomiaFilms - NO THANKS! I see what you're trying to spread around: Versatile + Digital = VD
I greatly appreciate the reverence for older technologies demonstrated in these videos as well as the humorous asides. Well done! Your technical explanations are a breath of fresh air.
Here's a random thought I had for you to ponder for your next video project: DVD Recorders. After you've finished recording your old videotapes to DVDs what other use can they serve besides playing DVDs? It might seem a bit silly, but I recently repurposed my recorder to play a collection of MP3 disks I had made a decade ago. By cobbling together an old PC subwoofer, an old CRT TV, an old pair of speakers and the recorder, I've essentially created a new sound system. It's a bit clunky, (I have to turn on all three devices individually first) but it works well and the quality of the sound is decent.