making an NTSC signal

[Hank Fletcher]

Can anyone help me get my head around making my own B/W NTSC signal? I haven't found much that's very informative on the web. It might be that I don't know enough about what I'm interested in to know what to search for. Not interested in PAL, just NTSC. And yes, I've read the wiki entry.

The part that's confusing me a bit is how the whole horizontal and vertical sync thing works in the timing. I'm having trouble finding a timing diagram that makes intrinsic sense or otherwise is properly documented.

How much leeway is there for accommodating certain parts of the protocol? For instance, I gather in PAL each horizontal scan line is exactly 64us, but in NTSC, each scan line is just slightly less than 64us. Would it be a big deal if I just round down to 63us, or will that just clip the right-side of the image a bit?

 

[kchriste]

Some NTSC info:
https://www.electro-tech-online.com/custompdfs/2008/06/lab4.pdf
You could do it with a PIC:
**broken link removed**
Or and AVR:
Video

 

[Hank Fletcher]

Thanks! The more info the better.

 

[crutschow]

How much leeway is there for accommodating certain parts of the protocol? For instance, I gather in PAL each horizontal scan line is exactly 64us, but in NTSC, each scan line is just slightly less than 64us. Would it be a big deal if I just round down to 63us, or will that just clip the right-side of the image a bit?

Slight change in the sync frequency probably won't affect a B&W signal. The exact frequencies are required for NTSC color since they are an integral multiple of the color 3.58MHz subcarrier frequency. Any deviation there would scramble the color.

 

[Nigel Goodwin]

You might try looking for the 'cheap video cookbook', and I seem to recall there was a later second book as well? - obviously far too old for PIC, but it contains very useful information for you.

 

[Hank Fletcher]

Slight change in the sync frequency probably won't affect a B&W signal.

Yeah, I thought there might be some leeway, and the Stanford lab kchriste linked to seems to confirm that. I'm not too fussy about colour, although I wish I understood it better. I guess I'll wait until ambition or necessity requires me to learn more about that!

You might try looking for the 'cheap video cookbook'

I think I found it!
Amazon.com: The Cheap Video Cookbook: Donald E. Lancaster: Books

 

[Blueteeth]

**broken link removed**
**broken link removed**


Both helped me to make a VGA/tv/LCD controller

Blueteeth

 

[crutschow]

Yeah, I thought there might be some leeway, and the Stanford lab kchriste linked to seems to confirm that. I'm not too fussy about colour, although I wish I understood it better. I guess I'll wait until ambition or necessity requires me to learn more about that!

The history of color television in the USA is very interesting. There was RCA's approach, which was compatible with the standard B&W signal, where they managed to stuff the color information into unused spectrum area of the allocated frequency band for the B&W signal. CBS had a color wheel system (rather like the way a single chip DLP TV displays color) which initially worked better than the RCA system but was not compatible with the B&W signal. Although the CBS system was initially approved for use, the refined RCA system eventually won out since it's signal could be received by all the B&W sets already in use without modification.

The curious slight changes in the horizontal and vertical scan frequencies resulting from incorporation of the RCA color system were to avoid generating beat frequency interference patterns on the screen between the B&W and color signals.