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24fps or 23.976fps?
Got to choose between two sources of the same movie for a restoration, one at 24fps and the other at 23.976fps.

I'd go with 24fps, because this version has two commentary tracks in AC-3, plus the lossless movie track in its original language; at the end, tracks from PAL DVD should be converted anyway, and *I think* 25->24 *should* lead to less "errors" than 25->23.976.

But, in other cases, if all audio tracks would be equal, I'd go with a 23.976fps version, because it seems that 99% of BDs (and WEB) versions follow this, AND it seems that some hardware players have some problems playing 24fps discs.

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I don't see where converting from 25 to 24 would have any quality difference from 25 to 23.976.  That said, if you are going to DVD and not BD, stick with 23.976.  I'm not aware of 24 fps being part of the standard.

From VideoHelp.com:
Up to 9.8 Mbit/s* (9800 Kbit/s*) MPEG2 video
Up to 1.856 Mbit/s (1856 Kbit/s) MPEG1 video
720 x 480 pixels MPEG2 (Called Full-D1)
704 x 480 pixels MPEG2
352 x 480 pixels MPEG2 (Called Half-D1, same as the CVD Standard)
352 x 240 pixels MPEG2
352 x 240 pixels MPEG1 (Same as the VCD Standard)
29,97 fps*
23,976 fps with 3:2 pulldown = 29,97 playback fps (NTSC Film, this is only supported by MPEG2 video)
16:9 Anamorphic (only supported by 720x480)
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24fps is what it plays as in cinema. It's also what Cinema DTS discs come in, timing-wise. But most Blu Rays and DVDs are synced to 23.976 (or rather, 24000/1001).

So it comes down to which audio you want to keep lossless from your sources. Maybe the best thing to go by is your lossy audio sources.

Let's say your main audio is lossless (DTS-HD MA or TrueHD), but your additional audio (which for example could be 24fps synced) is AC-3 and thus lossy, it may be actually less of a loss to retime your lossless audio to 24fps (because it's lossless to begin with and will also be delivered lossless, so your only loss is from the sample rate conversion), while in order to convert the AC-3 to 23.976 would either require wasting space on delivering it in a final lossless form (to not introduce more loss) or introduce generational loss by reencoding it in another lossy codec (or again as AC-3).

To give the example of Cinema DTS, I always retime that to 23.976 because the final format will be lossless anyway, so it doesn't matter much.

In the case of 25fps-synced stuff, that just doesn't leave you much of a choice, you will have to retime that anyway. The only choice there is the final delivery form. Lossless would be the only way to preserve the quality, but often the track just isn't important enough to justify that size, so you just accept the generational loss.

Whether to retime 25fps-synced stuff to 24 or 23.976, I think that honestly doesn't make much of a difference if you use a good SRC (sample rate converter). iZotope 64 bit SRC seems to be the best one from all I've read so far (its included in Sony/MAGIX Soundforge Pro).

From what you said about this project, I would also go with 24fps. It will preserve the commentary tracks nicely. Smile

Btw, I recently figured out that if you use ffmpeg for AC-3 conversion, the default setting uses DRC. You need to add the parameter "-drc_scale 0.00000" to disable DRC. Else you end up with garbage audio.
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@Doctor M: was talking about BD, as 24fps it's not DVD compliant. And, 24 is "round" while 23.976 is 24/1001 and for that should be "a bit more difficult" to convert - even if I'm sure nobody will ever say "Hey, I can hear it was converted from 25fps!" Big Grin

@Tom Arrow: sure, I'll convert the one with no (or less) lossy audio. I usually use the good ol' Aften - with DRC profile set to none; I think it's (still?) quite good, but open to suggestion for a supa-dupa converter! Wink
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Actually, are you sure 24fps isn't DVD compliant? I swear to God I thought I had some Japanese (?) DVD with 24fps on it. It was some weird format and behaved weirdly actually, I never bothered to figure out what exactly it was ...

Aften seems like it's good! Though it's a bit old now of course. If you ever feel like trying ffmpeg (it does a lot of other things too), the commandline would simply be:
ffmpeg -drc_scale 0.00000 -i input.ac3 output.flac

You can also just use .wav instead of .flac, but in that case I suggest you make a slight modification:
ffmpeg -drc_scale 0.00000 -i input.ac3 -c:a pcm_s24le output.wav

That's because ffmpeg by default chooses 16 bit for some reason for wav files. This extra command makes it go 24 bit.
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(2018-12-22, 01:48 PM)TomArrow Wrote: I swear to God I thought I had some Japanese (?) DVD with 24fps on it. It was some weird format and behaved weirdly actually, I never bothered to figure out what exactly it was ...

I once saw a Japanese DVD of The Thief and The Cobbler (which was actually the Miramax "Arabian Knights" cut) in anamorphic widescreen in OAR and progressive scan. It not only exhibited serious combing issues due to hard interlacing baked in from a shitty conversion, but had some screwy 3:2 flags that always resulted to a progressive 24fps rate (and not the usual 23.976) after removing pulldown with TSmuxer.

24fps and 23.976, without getting into 20 posts of how and why, are basically the same. Generally, 24 is the native shooting rate from the camera, and 23.976 is actually the rate that results from ether an ITVC conversion of a 29.97 interlaced telecine, or 4% slow down conversion of a 25fps source.
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