[FFmpeg-user] framerate conversion with sync audio

Carles Vila cvilad at gmail.com
Thu Oct 13 12:41:52 EEST 2016

> >
> > ffmpeg -i ...<your options here> -af atempo=0.96 <outfile>
> >
> > (24/25 = 0.96)
> >
> > Wow, I messed that one up completely. Incorporating Carl's suggestion as
> well of -vf setpts, the filter chain should look something like:
> ffmpeg -i <inputfile> -vf setpts=PTS*0.8 -af=atune=25/24 <codec options>
> <output file>
> or if -r works for you:
> ffmpeg -r 25 -i <inputfile> -af=atune=25/24 <codec options> <output file>

Hi, I have tested with the atempo filter and it certainly works! BTW I
think  atune does not exist..:) Thanks for pointing me in the right
direction though.
A drawback for me is the fact that this filter performs pitch correction.
Anyone know what algorithm is being used?
Anyway, this introduces artifacts and phase issues in multichannel audio
which are unacceptable in my case. I have further investigated and found a
filter chain that suits my need: asetrate, followed by aresample. To be
precise i have used

ffmpeg -r 25 -i input_24fps.mov -af asetrate=50000,aresample=48000 -c:v
prores -profile:v 3 -c:a pcm_s24le output_25fps_resampledaudio.mov

where 50000=48000*(25/24)

My only remaining problem, is that my original mov has 6 audio streams but
my process only processes and outputs the first.
How can I apply the same filter to all audio streams?
Thank you!!

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