CX on Laserdiscs: The Biggest Improvement Nobody Noticed - The Soundtracker
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- Опубліковано 3 жов 2022
- This video goes over the CX Noise Reduction system on Laserdiscs, showing what it does to the audio signal.
Disco con Tutti by Kevin MacLeod is licensed under a Creative Commons Attribution license (creativecommons.org/licenses/...)
Source: incompetech.com/music/royalty-...
Artist: incompetech.com/ - Розваги
LaserDisc content is the best content. Thank you for making this!
I agree, and thanks! I am glad you enjoyed it!
You are my kind of geek! What a great video... this helped answer a lot of questions for me. But I have more questions!!!
I appreciate it, thanks very much! There is a lot to cover, what would you like to know?
Almost too much to unpack in this forum. But I am curious about matrixed surround and cx on laserdisc. I have a copy of ET from 88, and was playing it recently through a 1969 sansui 4000 receiver. Im assuming im listening to the "basic" stereo mix that the studio created for non surround systems? Which sounds amazing by the way... the jacket also mentions it has an analog version of the soundtrack. So, they are managing to get digital and analog versions on the disc, plus the surround sound channels, im guessing left and right rear and a center channel. Understanding how the get all that on the disc almost requires and infographic to show how that's done. And, Im also curious why they worked so hard to not pay dolby. Were the fees that high, or just liked their own system better? (that's a start)
Note in the audio comparison @15:26 you can see the CX expansion working as well. Look at the waveform between 1:15 and 1:30. Notice how there is more dynamic range with the CX turned on.
Also note the video is also recorded as FM, 7mhz to 9mhz. Same as PAL type C VTRs (NTSC type C is 7-10mhz). It does not have a separate chroma RF carrier like Betamax and VHS, but the 3.58mhz chroma sidebands do extend down to the FM audio carriers at around 2.8mhz.
Great video! Unfortunately CX screwed up an early Criterion release of "It's a Wonderful Life". The movie itself is mono of course and there was an audio commentary on the right analog channel. But Criterion encoded both tracks with CX and that really messed up the audio (especially on the movie soundtrack). Whenever the person on the commentary track was talking, there was a "pumping" effect on the left audio channel. The audio was dropping and raising in volume all the time. CX only works on actual stereo material when using two channels. Basically the disc is unlistenable and you cannot turn CX off. But since it was already mastered that way, Criterion could never replace the discs (it was a special edition and very expensive at the time ☹️☹️).
I am only slightly glad to hear about this because everyone kept talking about "pumping" on forums and I have no idea what that sounds like. I may be able to find out, I just bought a copy of that film, was it the 50th Anniversary edition? there are a couple of different releases of "It's a Wonderful Life" on LD
Really interesting comparison ! I had wondered a lot about that, although i use the digital tracks whenever possible. Only 'nit pick' is the Dolby Digital on the disc is an AC-3 RF signal, which needs to go through a RF Demodulator before a 5.1 Bitstream is available.
Same, honestly usually when I am watching a Laserdisc it is either Digital Stereo or surround, I hardly ever use the analog tracks, and got curious about what I was missing. That kind of led me down the rabbit hole, so to speak.
Ah, yes. As for Dolby, I do wish a demodulator wasn't necessary, but after the initial expense and setup it kind of adds to the charm in my opinion.
hey me and you on the same laserdisc player vp-1000 I got mines for $85 off of Craigslist in 2019 ago still works like a champ😊
It's an awesome early player, really glad it is still working. It may be an older player, but it's become my favorite to use!
Great video, very informative. Keep 'em coming
Your on a mission from God.
No, CX decoding does not affect the Dolby Digital output.
The AC-3 RF tap must occur before the analog right channel signal ever goes to the audio demodulator circuit in the player, nevermind the CX decoder.
If you try to get Dolby Digital through the right analog audio output, whether it's connecting the right channel output directly to a digital input or connecting the right channel output to an AC-3 RF demodulator, it won't work because the signal has been corrupted by improper demodulation by the player at that point.
That's why you need a player with an AC-3 RF output to use with an AC-3 RF demodulator to get a usable Dolby Digital bitstream off of a Dolby Digital disc. The AC-3 RF demodulator has to handle demodulation of the right channel FM carrier in a manner that permits extraction of the Dolby Digital bitstream.
As for CX and monaural audio, it doesn't matter if the analog soundtrack is stereo or mono. CX can work either way. It is also possible to have a single analog channel with CX encoding while the other analog channel does not.
It's also possible for your Signature Collection copy of "The Blues Brothers" to have had a misprint on the jacket; it may say that it has CX, but it may actually not. Misprints that misidentify technical aspects of a LaserDisc has happened before.
I decided to check a few of my Dolby Digital encoded LDs’ from my vast collection of them and not one has a mention of CX on the jackets or disc. I assume the Blue’s Brothers Signature Edition is essentially as you said, a typo (and my copy has the same typo as well).
I had the same experience with mine, I have a handful of Dolby Digital encoded ones and that is the only copy in my collection that has that mark. Since CX does not work in mono, and I do not hear the "pumping" effect that others seem to hear, I am pretty sure it is a typo.
One question I have about your explanation about how video and audio is stored on LaserDisc, with how it’s stored, is it possible to get S-video out of a laserdisc player, or is it encoded differently as to where it will only work for normal composite video, if fed through an IC?
Laser disk uses direct color FM recording just like reel to reel broadcast VTRs did. The full composite signal is FM modulated and put on the disk. The playback involved demodulating that FM carrier to composite video. There is no separate chroma signal on the disk. So the composite video output is the cleanest you can get in theory. However some of the later players had comb filters to separate the chroma and apply analog noise reduction and image enhancement. So as the chroma has now been separated, why not throw an Svideo output on the back. But to get back to composite, the chroma and luminance had to be re-combined. So in many later players there is not a true off the disk composite video output as it goes through the comb filter. So all you can really do is to try both the Svideo output if it has one and then the composite on the display. Just use which ever looks better to you.