The Composite TV Signal (EP 23)
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- Опубліковано 15 жов 2024
- Doctor Plague explains what a composite TV signal is, and shows some examples.
See if you can find J.S. Bach before the end of the video! Be sure to watch to the end to see if you were correct!
There is now a part 2 to "The Composite TV Signal":
• The Composite TV Signa...
Category: Electronics, Technical
Additional Info: Color composite signal uses 15734.26 Hz for the horizontal scan frequency unlike black and white, which uses 15750 Hz. Color burst amplitude is 20 IRE or 0.143 volts (0.286 volts peak-to-peak).
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This is surprisingly underrated. Great job, and thanks for nice explanation!
Thanks for the kind comment!
After watching countless videos and reading articles, this video managed to explain in a simple and fun way a subject that was so complex. thanks!
Great to hear! Thanks!
Thank you for explaining how NTSC color works, I never understood it until this video! Would love to see you design some video generation circuits because I can't even picture how to start with that!
Thanks for the comment! I do plan on creating future videos showing how I have designed some composite video circuits. It may be a while before I get the time to create these videos (and I'll need to create some prerequisite videos), so please check back to see these future videos!
SECAM is a nightmare for broadcasters.
Great video.
Thank you!
I feel lucky to live in a country with PAL B/G TV instead of adopting SECAM or NTSC.
Good explanation about analogue TV.
Thank you!
Although PAL has a better color signal, NTSC was first, and switching to PAL would affect millions of TV owners. Clearly the FCC would never allow that to happen
Hi, Doc!
Man, you're really awesome!
Great content and very nice explanations.
Specifically about video signal, I would like to suggest some subjects that I believe (not just for me) will be very useful and complementary:
1. How to use the TV trigger found in some oscilloscopes;
2. How to trigger video signal in oscilloscopes that don't have specific TV Trigger function (using B Timebase, delayed sweep, or other tricks you know);
3. How to generate a simplest video signal (B&W and some color, if possible) using discrete (same great theoretical that you used on composite signal video) and using a microcontroller also;
4. Measurements with Vectorscope;
5. Differences between PAL, NTSC and SECAM.
Thank you very much for your videos!
I do have videos planned in the near future to cover point 3 that you listed. I will be creating both B&W along with color video circuits, both with 74-series logic (possibly some discrete transistors) and microprocessor-based circuits. I'm hoping they will be interesting videos. Thanks for the comment!
小时候玩FC游戏时非常惊叹为何仅一根黄色的信号线就可以传递如此复杂的画面，今天终于了解到了！感谢博士。不得不说，略懂一点数字电路的我觉得模拟电路真的很强。
Thank you!
This is fantastic. I’m following along with my oscilloscope and VCR.
Awesome, and thank you!
Ah, you forgot to mention those "secret" goodies that inhabit the vertical interval, like the VITS, VIR, modulated staircase, and 2T pulse...and the wonderful things they're used for!
Sorry, this video was only meant to be a basic introduction to the composite video signal. I didn't include all the test signals and such. This may be a subject for a future video. There are several things I haven't touched on yet: test signals, closed captioning, the change of frame rate from B&W to color, etc. Thanks for the comment!
This is a great style of teaching...you get right to the point and explain all the details 👍
I appreciate that! Thanks for watching!
Omg, this is such a good series! please continue making more of these videos! Thank you so much
Thank you for your interest!
Thank you that helped me a lot for my studies !
Greetings from Germany
Glad to hear it. Thank you for watching and Happy Holidays from us here in the U.S.!
dude this rules, thank you so much for the explanation
Thank you for the comment!
This has been very helpful while troubleshooting my DVD player doing some weeeeeeeird shit when trying to output colour. Thank you!
This is so good, especially the color burst part! You made it so simple to understand
Glad you think so! Thanks for watching!
That was an excellent and succinct description of a video signal. Bonus points for showing a genuine signal on a scope!
Wow! Thank you!
super fantastic explanation dude! I was looking this up in Wikipedia but did not get a good understanding of it. Thank you so much!
Thanks for the awesome comment!
What a great video doctor. This is the defintive guide of how pictures processors of old videogames works. Thanks for share your knowledge and explain to us very kindly.
Thank you for the kind comment!
Very interesting video. Thanks ❤
Next time, pks find a way to write on the white board without blocking the view.
But it was awesome to watch it explained so simple.👌👌
Thank you! In newer videos, I no longer stand in front of the whiteboard. Instead, I film from above. Cheers!
@@DoctorRGPlague thanks 🙏❤️👌
This is awesome, i had no idea, that composite video is such an easy thing to understand 😊
Glad you liked it! Thanks for the comment!
I'd seen other videos on this but didn't understand colour burst properly until this.
you make this all seem so easy! i'm trying to play with composite video signals to make my own video effects mangler and eventually a video synthesizer! would love a series on that subject if you have the knowledge! generating sync signals, generate your own R, G, B signals (simple shapes/patterns made with CMOS) and combine them with an RBG to NTSC chip. stuff like that please!!
Very good explanation of ntsc video signal. Thanks
love the snare!
A great introduction. If you have access to a waveform monitor and vectorscope, they would also be instructive. I'm sure you know about these, but have been out of video production a long time. I presume NTSC gear is pretty cheap/free.
I think some people might find the getup and demeanor annoying but I find it really endearing. Reminds me of old Bill Nye stuff, and is pretty unique compared to the usually fairly dry descriptions of things like this.
I think my biggest issues are some audio mixing issues (the intro/outro music is fairly loud in comparison to the main audio), your physical acting could do with some more variation (the outro felt kind-of stiff), and some more in-post visual aides wouldn't hurt (like visualizing the colour change as the colour signal's phase shifts from the colour burst's).
But otherwise damn keep it up. I'm really liking this style of teaching electronics stuff.
Thank you for your comment and constructive criticism! You may have noticed that I have not uploaded a video for a while now. I am taking some time off to enjoy the summer with Mrs. Plague. I do have more videos in the works, and will be uploading more in the future including more videos about electronics. So, please stay tuned for more future videos!
When I was a kid in the 80s I used to play with the vertical hold while watching broadcast TV or playing Atari 2600 or using the Commodore 64 to examine the vertical sync signals.
Sounds like something I would've done...the 80's were a great time! Thanks for watching!
Professional video monitors has a switch labeled "cross pattern" which enabled bothe the vertical interval and a delayed horizontal sweep to be displayed. This was used to adjust the tension on helical scan video tape machines. It was also used on 2" quad tape machines to align the delay lines to match studio sync to make fine adjustments for wipes/dissolves and other special effects.
I restore 2" quad broadcast video tape machines
Very informative video. I've worked on Televisions for years, starting right when solid state was just beginning...I've always wondered exactly how the color locked in, and TV's that has shifting colors that wouldn't lock in always frustrated me. Luckily, that was not a common problem. Now, I know how that color was locked in, Not always a bad crystal.
Thanks for sharing!
The crystal in a TV was a LOCAL oscillator thay go the TV "in the ballpark". The TV adjusts its oscillator to the transmitted burst signal, loke a Phased Locked Loop. If the transmitted signal is missing the burst, the TV will shut down its color circuitry, to produce a good B&W picture.
Not all programs back in the 60s were in color, so the master control at the TV station would switch on/off the burst signal when needed. If you sent burst with a B&W Image, your TV may display a weird tint, that's why it was shut off for a B&W program
This is wonderful!!!!!
Wow, thank you!
Informative video. Question: why did you have to add the resistor to simulate the input impedance of a TV when you hooked the VCR up to the scope? What would have happened if you just had the probes right to the RCA connector?
Hello and thank you for the question. Devices that output a composite video signal will expect to drive a 75-ohm load. Different devices may behave differently when there is no load (depending on how they were designed). I do have a video which demonstrates what happens when you leave the 75-ohm resistor out of the circuit and that video shows the result on an oscilloscope both with and without the resistor. This video shows the behavior of two different devices. You can find this video on my UA-cam channel - "How I Designed a Simple Video Sync Separator (EP 47)" from about 5:07 through 6:42 (minutes:seconds). Thanks for watching!
@@DoctorRGPlague Did you hook that resistor up in parallel? And what about the resistance already in the scope probe?
The resistor is connected from the composite video signal to ground. If you consider the oscilloscope probe to be the load, then the 75-ohm resistor is in parallel with the load. The effect of the oscilloscope probe impedance will be negligible when placed in parallel with a 75-ohm resistor. Typical probes will have an impedance of around 10-Megohms, which will decrease with higher frequencies, but we're not dealing with very high frequencies. Even if the impedance of the probe dropped to 1K-ohms, we'd still end up with about a 69-ohm parallel combination - not far from the intended 75-ohms. Thank you.
This mask is really funny; love it !
Thanks!
Very helpful 👌
Glad to hear it. Thank you!
Thank you, this made a lot of sense!
Glad it made sense! Thanks!
Pls continue with the old TV electronics.. Such info is very hard to find..
Back porches, front porches etc still exist on VGA. People continue to use them without understanding what they mean..
Nicely done Grim Reaper
Thank you for the compliment!
Nicely done! :D
Very clearly explained the signal! This is actually surprisingly similar to a digital bitmap file signal when forced into an audio wave!
Thanks for the comment!
Great job! Thank you!
very useful information. I was tuning up my VCR's video output card for a correct video signal output. I ran into this video. It's cool but what's up with the mask and the costume? is it really necessary?
I believe that is appropriate attire for His Bubonic Pustulency.
@@Pootycat8359 makes him irritating to watch
I may not be everyone's cup of tea. I am who I am. Thanks for watching!
@@DoctorRGPlague don't get me wrong. I like what you are doing. I will keep on watching. I beleive there is a worderful person under that mask. I just wished to see that person.
This is awesome
Thank you, much appreciated!
This is interesting, but, why are you showing old analog since it hasn't been used for several years?
Nice video. How about VGA signal? That one i hear is even easier to generate since it can be done with just digital output although you obviously then have only 8 colors.
Thank you for the kind comment! Yes, VGA could be easier to generate, especially for color, since it has separate color signals. You wouldn't need to worry about phase shifting for color generation. The syncs are generated with separate signals. You would be limited to only 8 colors if you used just 1 bit for each of the 3 color signals (1 bit = 2 voltage levels, so 2^3 = 8 colors). Thank you for the idea. I'll add it to my list of possible video ideas, and maybe in the future I'll make a video on the VGA signal!
How is the represented on a waterfall diagram?
Thank you for your video. I have a question about the fields. In your video, the first field takes 9+13+240+0.5 lines, and the second field takes 9+0.5+13+240 lines. Does it mean that the second field is lower than the first field, if the TV scan lines from top to bottom?
Hello and thank you for your question. The top of the second field is drawn one scan line lower than the top of the first field. Both fields occupy the entire height of the screen, meaning that the first field does not fill only the upper half of the screen and the second field does not fill only the lower half of the screen. Instead, the first field fills in the odd numbered lines - lines 1, 3, 5, etc. Then the second field comes along and fills in the gaps by filling in the even numbered lines - lines 2, 4, 6, etc. This is called interlacing. This helps with persistence of vision by doubling the frame rate and reducing flicker. I hope I was able to answer your question. FYI - I am planning on creating a series of videos that demonstrate how to make a composite video generator circuit to display text and graphics on an analog TV, which may be of interest to you. However, it may be a while before I am able to create those videos, and I need to create some prerequisite videos first, but I hope to start uploading those videos before the end of the year. Thank you for watching!
@@DoctorRGPlague Thank you for replying. Talking about “real composite signals”, I wonder if I can see something about retro video consoles. I heard that they used a technique called 240p, and I could guess that they achieved it by sending V-sync pulses not alternatively between at beginning of a line and at center of a line, but always at beginning of a line, so scanlines always hit same places of the monitor. What I could not guess is, on which line (or timing) do they send V-sync signals? If I had to take a wild guess, I’d say that they send V-sync at Line 262, Line 263, Line 262, Line 263, ... alternatively, in order to make 525 lines for every 2 fields, but it is just my guess. I’ve been always curious about how they actually work.
There is more than one way to generate 240p. It is something that I have generated in the past. Let me explain. If you look at the generated lines (for 480i) that I listed on the white board, you'll notice there is one difference between the two fields. The difference is the half lines. You can see that they are in different locations for the two fields. In the first field the half line is after the picture is drawn, but in the second field it is before the picture is drawn. This is what causes the interlacing. The half line in the second field creates a short delay that places the following lines in between the lines of the first field. So, the half lines create the interlacing. If you want 240p then all you need to do is get rid of the half lines. Then both fields will be exactly the same. Since they are the same you can just throw one of the fields away, and you are left with one field that you keep repeating. The lines for this method are: 6 EP, 6 VSP, 6 EP (these 18 lines are at 2 times the frequency and actually occupy 9 full lines), 13 blank lines, and 240 picture lines. This gives 262 total lines for 240p. We do not need 525 lines, so for 240p you would have 524 lines after 2 frames are drawn. By the way 480i would be 30 frames per second (fps) since you need two fields per frame, and 240p would be 60 fps since you need only one field per frame. Alternatively, you could just throw away the second field of the 480i and keep repeating the first field (262.5 lines each time, which would preserve the 525 total after two frames are sent). But please do not alternate the number of lines each time between 262 and 263, you'll get a shaky image. Make sure each field you send has the same number of lines. Hopefully this helps. I believe the old Atari 2600 used 240p, and I have one stored away somewhere. If I can find it and if it still works, then maybe I'll make a future video to demonstrate how the 2600 produced 240p. That could make an interesting video, so I'll keep it in mind. Thanks.
Awesome! Are you able to do a video on Component (YPbPr)? Would be interested to see that!
And Dsub also
Thanks for the suggestion!
I always wanted to know how the color composite signal is built up, but never got the answer.
Moreover, I never thought that a bird will explain to me such a way that I could understand. Unbelievable! What kind of World are we living in?
(a small addon: it took 30+ years)
Well, you know what they say...the bird is the word! Thanks for watching!
It's AETBX message
Who thinks this is the guy responsible for the Max Headroom broadcast incursion?
You can take video about SÉCAM video
Sorry, but I'm not familiar with SECAM. Thanks for watching!
SECAM only difference is the colour signal modulated in FM instead of QAM which are used on PAL and NTSC.
How funny
Thanks for watching!
WTH???