[HN Gopher] Why 23.976 and not 24 FPS? ___________________________________________________________________ Why 23.976 and not 24 FPS? Author : mfiguiere Score : 24 points Date : 2022-10-09 21:23 UTC (1 hours ago) (HTM) web link (cinematography.com) (TXT) w3m dump (cinematography.com) | lykr0n wrote: | The amount of hidden engineering in Analog systems is mind | blowing. Imagine how many hours were spent in a lab figuring out | the exact right timings, chemical mixtures, and circuit design | needed to make modern Cinema exist as we know it. | nmilo wrote: | Sometimes it makes me sad how "boring" digital transmission is. | Just pack up your data and send it over IP. Life is too easy. | petee wrote: | Great answer for where 29.97 came from, but I seem to be missing | the explanation of 23.976 fps which is suddenly introduced as | just an effect of audio post, but not how or why exactly... | | Edit: more specifically, if audio was being converted to NTSC for | dailies, why would it be 23.976 and not 29.97? | johntb86 wrote: | The traditional frame rate for film is 24fps, which is | converted using 3:2 pulldown to 30 fps. 23.976 fps converts | using 3:2 pulldown to 29.97 fps (23.976*30/24=29.97). | Tempest1981 wrote: | While reading about 3:2 pulldown, I saw that for PAL (25 fps) | there is 2:2:3:2:3 pulldown to 30 fps. | dylan604 wrote: | but rarely does anyone actually do this. normally, a 4% | speed change is done to get the frame rate to match. as for | the audio, it totally depends on how much effort someone | put into it to correct the pitch so that the frequencies | are the same in both frame rates. typically, nope. things | sound higher pitched in 25fps than they do at the original | 24 or 24000/1001 frame rates | [deleted] | assttoasstmgr wrote: | Because audio for 23.976fps _film_ is playing at the same speed | as 29.97fps _video_. Which is really interlaced video at 59.94 | _fields_ per second. 3:2 pulldown is used to synthesize extra | video frames to transfer to NTSC video so for a given instance | of time, for every 4 frames of _film_ you get 5 frames of | _video_. (23.976 /29.97 = 4/5) The instance of time remains | unchanged so the audio is playing back at the same speed. This | is all inherited from the CRT days before progressive video | playback on flatscreens, and the video fps was tied to the | local electrical frequency (50 Hz in Europe vs 60 Hz in USA / | Japan) which is how the CRT timings were derived. | | Coincidentally PAL video plays back at 25fps, to convert film | to PAL they just speed it up from 24 to 25fps, audio and all, | which is why if you watch a Euro DVD release of the same film | all the actors sound like they just ingested helium before the | scene because the audio is playing back ~4% faster. | cammikebrown wrote: | It's the same ratio. 30/29.97 = 24/23.976 ___________________________________________________________________ (page generated 2022-10-09 23:00 UTC)