How do I change back PAL 25 fps video files with correct audio to 24 fps

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1

Hi!

So in the GUI if I select 24p for video in the default duration/fps option it will correct the video.

How do I do the same for audio? The same field is disabled. Adding 24/25 in the “stretch by“ option doesn’t seem to have an effect. So The audio is faster and pitch shifted.

(I guess an analogous change would be to change the sampling rate to 46080Hz, but I never saw such an option)

2

I’ve converted from 25 to 24 and 24 to 25 many times. First demux your audio and video to separate files, change the framerate of the video using mkvtoolnix and then load the audio file into something like Audacity and change the speed - I then export the speed/pitch-corrected audio to multichannel FLAC and remux with the corrected video. I can’t imagine that re-timing the audio tempo/pitch can be done with mkvtoolnix as the source audio is typically in bitstream packets and has to be converted to PCM for downstream processing, but it certainly can with Audacity.

3

Thanks. A tad disappointing. It’s so easy to modify the video frame-rate in comparison.

4

there is a lot involved in reprocessing the audio if you don’t already have a framerate-matching audio track to mux back in. For example, I’ve converted 24p to 25p for some BBC blurays. When converting the audio we have to consider whether the 24p version had pitch correction or not. If it didn’t, I use the change speed/pitch effect in Audacity. If it did, I use change tempo. Figuring out which one is correct can be a matter of judgement, but typically if the pitch is wrong I find that obvious. When going from 50i to fix PAL speedup on DVDs (and rarely, on blurays) I always find that the pitch needs to be dropped, so use the speed/pitch effect for that.

If you can get Audacity installed (it will need ffmpeg to import DTS etc) I’m happy to help, if you might end up doing this a lot then climbing the learning curve may be worth it.

5

I just meant it’s unfortunate that there isn’t an easy fix. Like telling the decoder via metadata to play it slower same as with video by setting 24fps. So I guess sound processing it is then.