4 ms·

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

by petee 4y ago

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?

cammikebrown 4y ago
It’s the same ratio. 30/29.97 = 24/23.976
johntb86 4y ago
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 4y ago
  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 4y ago
    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
    - anigbrowl 4y ago
      I remember living in the UK 20 years ago when my friend had got into Buffy the Vampire Slayer. He insisted I watch some episodes. But because the target demographic was 'nerdy night owls' on a non-prestige TV channel, they cheaped out on the conversion and by the end of each 45 minute episode the dialog had gone badly out of sync. My friend insisted I was just imagining it, but only one of us went on to have a career doing post-production in the US market. To be completely frank I've looked down on UK/EU broadcast techs a little ever since because being able to set everything to 25fps and forget about it is easy street.
      - dylan604 4y ago
        I've made a career of taking pull down sequences out of videos to prep for DVD->Blu-ray->streaming. Where others have failed, I have properly restored. "Others" for example are FAANG's streaming services. Everyone wants it to be a single button IVTC, "set it and forget it" like you said. Shot on 24fps film, edited at 29.97 with pull down where every edit is a break in cadence, 30i graphics/bumpers, and some shows (I'm looking at you The Shield) where they shot 30fps film for a special look/feel during certain scenes, and a set-it-forget IVTC will not do well at all.
      - ajanuary 4y ago
        > To be completely frank I've looked down on UK/EU broadcast techs a little ever since because being able to set everything to 25fps and forget about it is easy street. My experience has been the reverse. Because they can, people in UK/EU have historically cared much more about frame accuracy. It’s only in the last 10 years or so that people in North America have started caring about frame accuracy. In the past it’s been quite hard to do because of the non integer frame rate.
    - axiolite 4y ago
      Parent was obvious talking about converting 25fps PAL video to 30fs NTSC frame rate, which happens ALL THE TIME... NOT about converting from film to PAL. You are arguing with no-one.
      - dylan604 4y ago
        Yes, I have no idea what I'm talking about. I forget that sometimes. However, maybe you've forgotten that a lot of 25fps was shot progressive so 25psf more than 50i so that the video conversion was 25->24->29.97 which happens all the time as well. Glad to know there's an expert on the boards I can have second guess me though. I'll hit you up next time I might think I know something from 30 years of experience
        axiolite 4y ago
        > Glad to know there's an expert on the boards I can have second guess me though. I'll hit you up next time I might think I know something from 30 years of experience I suggest you get over yourself. I am indeed a video expert with decades of IVTC experience. The first line of your reply was: "but rarely does anyone actually do this" That is factually incorrect, no matter how many years of experience you may have.
deleted 4y ago
[deleted]
assttoasstmgr 4y ago
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. This was largely fixed with Blu-Ray as films play back at their native rate[1] on progressive displays but our European friends who have only seen films on VHS/DVD or TV and not in the theatre or Blu-Ray have been done a disservice, because the video and audio is sped up on playback and not as the director intended it to be shown. [1] A notable exception is some unscrupulous distributors abroad release shitty PAL 25fps Blu-Rays of films which are simply upscaled PAL DVD versions that they then market as Blu-Ray but are worse than DVD quality but at marked up prices. This is more common than you think. Official releases from the studios are encoded at 23.976fps on the disc. TV shows shot on PAL video (native 25fps) will always play back at 25fps.
- gsich 4y ago
  Pitch correction exists.
  - deleted 4y ago
    [deleted]
  - garaetjjte 4y ago
    It's not straightforward and might introduce artifacts.
    - lecoyote418 4y ago

by petee 4y ago

cammikebrown 4y ago

It’s the same ratio. 30/29.97 = 24/23.976

johntb86 4y ago

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 4y ago
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 4y ago
  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
  - anigbrowl 4y ago
    I remember living in the UK 20 years ago when my friend had got into Buffy the Vampire Slayer. He insisted I watch some episodes. But because the target demographic was 'nerdy night owls' on a non-prestige TV channel, they cheaped out on the conversion and by the end of each 45 minute episode the dialog had gone badly out of sync. My friend insisted I was just imagining it, but only one of us went on to have a career doing post-production in the US market. To be completely frank I've looked down on UK/EU broadcast techs a little ever since because being able to set everything to 25fps and forget about it is easy street.
    - dylan604 4y ago
      I've made a career of taking pull down sequences out of videos to prep for DVD->Blu-ray->streaming. Where others have failed, I have properly restored. "Others" for example are FAANG's streaming services. Everyone wants it to be a single button IVTC, "set it and forget it" like you said. Shot on 24fps film, edited at 29.97 with pull down where every edit is a break in cadence, 30i graphics/bumpers, and some shows (I'm looking at you The Shield) where they shot 30fps film for a special look/feel during certain scenes, and a set-it-forget IVTC will not do well at all.
    - ajanuary 4y ago
      > To be completely frank I've looked down on UK/EU broadcast techs a little ever since because being able to set everything to 25fps and forget about it is easy street. My experience has been the reverse. Because they can, people in UK/EU have historically cared much more about frame accuracy. It’s only in the last 10 years or so that people in North America have started caring about frame accuracy. In the past it’s been quite hard to do because of the non integer frame rate.
  - axiolite 4y ago
    Parent was obvious talking about converting 25fps PAL video to 30fs NTSC frame rate, which happens ALL THE TIME... NOT about converting from film to PAL. You are arguing with no-one.
    - dylan604 4y ago
      Yes, I have no idea what I'm talking about. I forget that sometimes. However, maybe you've forgotten that a lot of 25fps was shot progressive so 25psf more than 50i so that the video conversion was 25->24->29.97 which happens all the time as well. Glad to know there's an expert on the boards I can have second guess me though. I'll hit you up next time I might think I know something from 30 years of experience
      - axiolite 4y ago
        > Glad to know there's an expert on the boards I can have second guess me though. I'll hit you up next time I might think I know something from 30 years of experience I suggest you get over yourself. I am indeed a video expert with decades of IVTC experience. The first line of your reply was: "but rarely does anyone actually do this" That is factually incorrect, no matter how many years of experience you may have.

deleted 4y ago

[deleted]

assttoasstmgr 4y ago

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. This was largely fixed with Blu-Ray as films play back at their native rate[1] on progressive displays but our European friends who have only seen films on VHS/DVD or TV and not in the theatre or Blu-Ray have been done a disservice, because the video and audio is sped up on playback and not as the director intended it to be shown. [1] A notable exception is some unscrupulous distributors abroad release shitty PAL 25fps Blu-Rays of films which are simply upscaled PAL DVD versions that they then market as Blu-Ray but are worse than DVD quality but at marked up prices. This is more common than you think. Official releases from the studios are encoded at 23.976fps on the disc. TV shows shot on PAL video (native 25fps) will always play back at 25fps.

gsich 4y ago
Pitch correction exists.
- deleted 4y ago
  [deleted]
- garaetjjte 4y ago
  It's not straightforward and might introduce artifacts.
  - lecoyote418 4y ago