[beefok]

I love all of your projects, Fabien!

This SNES video analysis one is incredible. I've always had all of this stuff running around in my head for how to explain how weirdly cool video generation for NTSC is, and you have done an incredible job finding a way to do so.

There is yet another reason for the weird frame and horizontal scan rate. When NTSC was originally introduced as a broadcast standard over a single RF modulated signal, the sound carrier and signals were also embedded in the signal as well. [1] Actually, I just found that Wikipedia does a good job of describing this on the NTSC page [2]:

    When a transmitter broadcasts an NTSC signal, it amplitude-modulates a radio-frequency carrier with the NTSC signal just described, while it frequency-modulates a carrier 4.5 MHz higher with the audio signal. If non-linear distortion happens to the broadcast signal, the 3.579545 MHz color carrier may beat with the sound carrier to produce a dot pattern on the screen. To make the resulting pattern less noticeable, designers adjusted the original 15,750 Hz scanline rate down by a factor of 1.001 (0.1%) to match the audio carrier frequency divided by the factor 286, resulting in a field rate of approximately 59.94 Hz.

So yes, yet another difficulty with NTSC -- sound actually splattered visual noise on the screen as well!

[1] https://upload.wikimedia.org/wikipedia/commons/f/fd/Ntsc_cha... The combined spectrum of video, sync, and audio all on a single RF broadcast signal.

[2] Search for 'sound carrier' in https://en.wikipedia.org/wiki/NTSC#Color_encoding