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Old 13th June 2023, 07:00   #1  |  Link
moutezz
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Framerate issue 24 to 23 or the opposite ?!

Hi everybody... I hope you're doing great.

So... let's do it quickly lol

I know the subject has been asked a million times but I m sorry I have to ask it for help...

I have to separate files, an mp4 1080p 24.000 FPS video and a AC3 audio 23.976 FPS... the two are the same and it have the same duration... but different FPS. I have to duplicate both in one file but before I have to convert either the video to 23.976 FPS without messing with the quality or convert the audio to 24.000 FPS.
My question is what a good and useful software I have to use to achieve that ? PLS help...

I need some advice or suggestion of some softs but MeGui... I used it without one result.

THANK U
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Old 13th June 2023, 08:05   #2  |  Link
tebasuna51
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Quote:
Originally Posted by moutezz View Post
...I have to separate files, an mp4 1080p 24.000 FPS video and a AC3 audio 23.976 FPS...
Video have Frames Per Second but audio have Samples Per Second, normally 48000 and don't need be the same of course.

If video and audio have the same duration probably they are in sync and you can mux them. If not we can't know if you need delay and stretch or a more complex edit.
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Old 13th June 2023, 20:14   #3  |  Link
moutezz
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Originally Posted by tebasuna51 View Post
Video have Frames Per Second but audio have Samples Per Second, normally 48000 and don't need be the same of course.

If video and audio have the same duration probably they are in sync and you can mux them. If not we can't know if you need delay and stretch or a more complex edit.
Did you at least understand what I said ?!!!!!!!!!!!!!!!!!!!

It's not a question of duration, it's a question of framerate... the audio I have is from another video of 23.976 FPS and the actual video I have which I want to duplicate is 24 FPS... they can not be mux because it's going to be a desync... I need kind of trick to sync the video and the audio.
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Old 13th June 2023, 20:38   #4  |  Link
StainlessS
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As Teb said, audio does not have a FPS.

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they can not be mux because it's going to be a desync...
Have you tried it.

Quote:
Did you at least understand what I said ?!!!!!!!!!!!!!!!!!!!
I imagine that Teb does understand you and is trying to help you despite you're making it difficult.
Teb is pretty much the site audio expert (but most people here could have told exactly the same thing).
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Old 13th June 2023, 20:53   #5  |  Link
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Quote:
Originally Posted by moutezz View Post
Did you at least understand what I said ?!!!!!!!!!!!!!!!!!!!

It's not a question of duration, it's a question of framerate... the audio I have is from another video of 23.976 FPS and the actual video I have which I want to duplicate is 24 FPS... they can not be mux because it's going to be a desync... I need kind of trick to sync the video and the audio.
As already stated, it's all about duration, framerate is irrelevent. If the duration is identical, mux them and they will be in sync. If the duration is not identical, then dealing with the audio is your best option and there are tools to do that. But, as again already stated, try it first before insulting someone who is trying to help and has probably forgotten more about it than you will ever know!
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Old 15th June 2023, 23:42   #6  |  Link
moutezz
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Originally Posted by john33 View Post
As already stated, it's all about duration, framerate is irrelevent. If the duration is identical, mux them and they will be in sync. If the duration is not identical, then dealing with the audio is your best option and there are tools to do that. But, as again already stated, try it first before insulting someone who is trying to help and has probably forgotten more about it than you will ever know!
Actually they’re not in sync... why's that ?
At first I said they were in sync and now I say the opposite, because before I demux the video with the audio I don't need, the duration of the movie was 01:55:33 but no the video has the duration of 01:55:27 wich make them desynchro and my though stay the same... how can I convert the audio to fit with the video... ?

I heard that you can change the framerate of the video without having to convert it... is this possible ?

THANK YOU

Last edited by moutezz; 16th June 2023 at 18:00.
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Old 16th June 2023, 07:51   #7  |  Link
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Remux it with MkvToolNix
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Old 16th June 2023, 18:12   #8  |  Link
moutezz
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Remux it with MkvToolNix
Remux what with what ?

If you were talkin' about the actuall video and audio I answer you the same... I don't need to Remux them because they are desynchro... why u insist to remux two desynchro media ? I don't need to remux them, I can tell without doing this operation... you want to know how ?

Simple... I open the video with any capable reader software and I join the audio to video and guess what...... they are desynchro !
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Old 16th June 2023, 19:20   #9  |  Link
moutezz
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The mkvtoolinix thing I try it before... it doesn't work... the difference between the audio and video stay the same... and I just tried it again. Nothing new.
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Old 16th June 2023, 22:01   #10  |  Link
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Being out of sync can mean the video and audio don't start together. A different video may have more more black frames at the beginning or the studio logo might display for a few frames longer. If it's that sort of de-sync then you need to apply a delay to the audio stream when muxing with MKVToolNix to compensate. A positive or negative delay can be used, depending on whether the audio starts too early, or if it starts too late.

Being out of sync can also mean the video and audio drift apart as the video progresses. To fix that you'd need to adjust the video frame rate to compensate for the fact the audio and video are running at slightly different speeds. It might only mean changing the video frame rate from 24fps to 23.998fps or you might have to change it from 24fps to 23.976fps, or something..... you'd have to experiment.

Assuming the video and audio can be matched up exactly, it's possible you'd need to apply an audio delay so the video and audio start in sync, and also adjust the video frame rate so they end in sync too.

The video and audio streams don't have to be the same length, so the video on it's own might appear to have a different duration than when they're muxed together. That doesn't necessarily mean they're in sync or they're not. They might just have different lengths.

Anyway, what you need to do is work out if the audio and video sync changes over time, getting further apart as the video progresses, or if they start de-synced by a specific amount of time and they're still de-synced by the same amount of time at the end. Or if it's a combination of both types of de-sync. It can be hard to get it right and it often involves a lot of trial and error, assuming of course it is possible to sync them, which it may not be. Nobody can tell you for sure, or tell you exactly what you need to do.

Last edited by hello_hello; 16th June 2023 at 22:17.
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Old 17th June 2023, 10:12   #11  |  Link
tebasuna51
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Quote:
Originally Posted by moutezz View Post
... audio... duration of the movie was 01:55:33, but the video 24 FPS has the duration of 01:55:27...

I heard that you can change the framerate of the video without having to convert it... is this possible ?
Of course my answer about MkvToolNix is change the video FPS 24 to 23,976 and then match (1:55:27 * 24 / 23.976) ~ 1:55:33 the audio duration.

But, like hello_hello say, that can't guarantee a perfect resync because can have initial delays or even different video cuts.

For instance one can be from a BD source and other from a TV capture with commercials cuts, the last video can't exactly match the original from BD and need a complex edit.

Like you can see don't exist a unique solution for all, each need a proper way. Answer that:

1) How many time (+ or -, try to be exact: +1.3 sec at 00:01:54) are desync at the begining of the movie.

2) How many time (+ or -, try to be exact: +7.2 sec at 01:50:14) are desync at the end of the movie.

(+ the audio play after the video)
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