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grishkayesterday at 2:39 PM1 replyview on HN

I grew quite an appreciation of color TV recently when I made a software-defined SECAM decoder. It's mind-boggling that they were able to do this with 60s technology, to be honest. But then what do I know, analog electronics is witchcraft to me :D

https://github.com/grishka/miscellaneous/blob/master/AVDecod...

edit: I watched the video. It only took them until the 13th minute of a 15-minute video to show something resembling a real video waveform, lol. That's, uh, not how you explain how TV works.


Replies

pavlovyesterday at 2:56 PM

SECAM was pretty crazy because it required a delay line: a memory that would hold the previous scanline so it can be combined with the current one.

Without digital circuits, the delay line was a piece of glass. You’d convert the video signal to a sound wave, send it through the glass, and (hopefully) get it back exactly 64 us later so it aligns with the next scanline.

Here’s a picture: https://www.eevblog.com/forum/projects/glass-ultrasonic-dela...