Comment by iso1631
10 hours ago
Originally you had 30fps, it was the addition of colour with the NTSC system that dropped it to 30000/1001fps. That wasn't a decision taken lightly -- it was a consequence of retrofitting colour onto a black and white system while maintaining backward compatibility.
When the UK (and Europe) went colour it changed to a whole new system and didn't have to worry too much about backward compatibility. It had a higher bandwidth (8mhz - so 33% more than NTSC), and was broadcasting on new channels separate to the original 405 lines. It also had features like alternating the phase of every other line to reduce the "tint" or "never twice the same color" problem that NTSC had
America chose 30fps but then had to slow it by 1/1001ths to avoid interference.
Of course because by the 90s and the growth of digital, there was already far too much stuff expecting "29.97"hz so it remained, again for backward compatibility.
An engineer at RCA in New Jersey told me that at the first(early) NTSC color demo the interference was corrected by hand tweaking the color sub-carrier oscillator from which vertical and horizontal intervals were derived and the final result was what we got.
The interference was caused when the spectrum of the color sub-carrier over-lapped the spectrum of the horizontal interval in the broadcast signal. Tweaking the frequencies allowed the two spectra to interleave in the frequency domain.
60 interlaced fields per second, not 30 frames per second. The two fields do not necessarily contribute to the same frame.
If you get those fields out of sync, you will have problems though, so it's okay to consider them in pairs per frame for sanity's sake.
In the UK the two earliest channels (BBC1 and ITV) continued to broadcast in the 405 line format (in addition to PAL) until 1985. Owners of ancient televisions had 20 years to upgrade. That doesn't seem unreasonable.
understanding the affect of the 1.001 fix has given me tons of job security. That understanding came not from just book learning, but OJT from working in a film/video post house that had engineers, colorists, and editors that were all willing to entertain a young college kid's constant use of "why?". Then being present for the transition from editing film on flat beds to editing film transfers to video. Part of that came from having to transfer audio from tape reels to video by changing to the proper 59.94Hz or 60Hz crystal that was needed to control the player's speed. Also had a studio DAT deck that could slow down the 24fps audio record in the field to playback at 23.976.
Literally, to this day, am I dealing with all of these decisions made ~100 years ago. The 1.001 math is a bit younger when color was rolled out, but what's a little rounding between friends?