A 24.000 fps WEB release of a movie, nice!
Movies are shot at 24.000 frames per second. Because that's what the motion picture industry standardized on. Even today, all pro equipment will shoot at 24.000 fps.
The movies are slowed down to 23.976 fps for consumer devices (so not in cinemas, that's pro equipment). The purpose used to be to allow 3/2 pulldown into 29.970 fps or 59.940 fields per second interlaced, like @normandy said, so movies could be televised.
Since there are practically no analog devices left, this is unnecessary and is purely kept as inertia is pushing it along.
Consumer media in ex-NTSC countries in *general* (but not always) have 23.976 fps due to this inertia. Consumer media in ex-PAL countries will also in *general* not have a slowdown for cinematic features hence the movies will be left as-is without audio resampling.
This inertia also carried over to the web streaming world unfortunately. Streaming providers work with whatever they're given (usually huge huge ProRes files from BD mastering), but now always (if a release isn't going to be released on BD it might be kept as-is). There is usually no special stream-only and BD-only mastering, unless its some rerelease/remaster.
So, due to this inertia carrying over into the streaming world, and most BD rips being from NTSC countries, its nice to find non-slowed and non-resampled movies with an integer frame rate.
Note, 1000/24.000 is still irrational. And the reason I mention 1000 is that the default matroska timebase is 1m, which is what this movie came in from our good pirate friends. MP4, which is the usual format used, has less issue with timebase rounding (but doesn't support sane subtitled).
So its not so much a technical thing (as both 24.000 and 23.976 can be represented exactly in MP4, however the latter _will_ have its audio resampled, which can be awful) as it is a nice surprise, since someone either paid attention to streaming, or the stars aligned, or its a non-US/JP movie.
@thatbrickster @duponin @normandy As I said, media is slowed down to 23.976. For video, it doesn't make a difference or sense to resample. For audio however, it does, as 440/1.001 has a big enough deviation to be heard. They didn't used to be, but now since we have the computational resources, we do.
Audio resampling is a solved problem. Just use SoX. But is some random professional production company going to use proper open-source resampling? Probably not, they might just use some cheap bilinear resampling.
This can create problems, as demonstrated in Kimi no na wa/Your Name's JP/US releases, which had the audio horribly horribly resampled and practically ruined on JP/US BDs, but some EU BDs were fine. IIRC the Italian BDs were the best.
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