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Comment by MoonWalk | Hacker News Reader

You should read about the invention of color television. There were two competing methods, one of which depended on a spinning wheel with colored filters in it. If I remember correctly, you needed something like a 10-foot wheel to have a 27-inch TV.

Sure enough, this was the system selected as the winner by the U.S. standard-setting body at the time. Needless to say, it failed and was replaced by what we ended up with... which still sucked because of the horrible decision to go to a non-integer frame rate. Incredibly, we are for some reason still plagued by 29.97 FPS long after the analog system that required it was shut off.

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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.

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.

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.

Which unfortunately also has continued to plague us much longer than we have used any display technology where that might have made any sense.

Yep, once again thanks to broadcasters spreading FUD. When the progressive vs. interlaced debate raged during the development of ATSC, broadcasters whined that progressive would disrupt their entire production pipeline... which was utter BS because they'd been showing film-based content for generations.

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?

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.

I understand the origin of the 29.97 frame rate. They did have a choice, though: Shift the audio signal's frequency and orphan the (relatively limited number of) receivers at the time, or saddle generations of people with this dumb frate rate.

Why is an integer frame rate better?

For one thing, it’s much easier to measure spans of time when you have an integer frame rate. For example, 1 hour at 30fps is exactly 108,000 frames, but at 29.97 it’s only 107,892 frames. Since frame numbers must all have an integer time code, “drop-frame” time code is used, where each second has a variable number of frames so that by the end of each measured hour the total elapsed time syncs up with the time code, i.e. “01:00:00;00” falls after exactly one hour has passed. This is of course crucial when scheduling programs, advertisements, and so on. It’s a confusing mess and historically has caused all kinds of headaches for the TV industry over the years.

In addition to the other poster's on-point remarks, film cameras have always run at integer frame rates. We have generations of motion pictures shot at 24 FPS.

Many TV shows (all, before video tape) were shot on film too, but I'm not sure if they were at an even 30 FPS.

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