Re: [Avid-L2] 29.97 and HD / RANT

"For the USA, the TV NTSC color encoded system devised in the late 1930s had to make sure video and audio frequency signals did not interfere with each others when transmitted (ie audio creating a visual pattern). Hence the engineers decided to adjust the video carrier by a factor of 0.1% to avoid intermodulation between video and audio signals."

Perhaps I'm misremembering but the shift to 29.97 was based on the the color subcarrier frequency and it's relationship with the horizontal scan rate.  The subcarrier needed to be an odd multiple of one half the line frequency so that the any influence the color information might have on luminence would be cancelled out by the neighboring line. 

The audio was FM and transmitted at 4.5 MHz above the video carrier.  Video was amplitude modulated and audio FM modulated.  It was when video excursions from high level video made the video information encroach into the audio carrier frequency we heard buzz.

I'm enjoying all this info and if my recollection is inaccurate please refresh my memory.

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