On Tue, Oct 11, 2016 at 4:25 PM, Carles Vila <[email protected]> wrote:
> Hi, I'm trying to perform framerate conversion of a video, from 24fps to > 25fps to be precise. > The source is mov, ProRes with multichannel audio at 48kHz. > It is mandatory for my application to preserve the integrity of all frames, > i.e. no frame-interpolation or duplication should occur. > In other words, just the playback speed should be increased from 24 to 25, > resulting in a video of slightly shorter duration. > I've been partially successful so far using the command > > ffmpeg -r 25 -i <inputfile24fps.mov> -r 25 -c:v prores -profile:v 3 -c:a > pcm_s24le <output_25fps.mov> > > This comand produces a good video, shorter than the original, but the > problem is with audio. As you can imagine, the audio drifts out of sync > because it has no knowledge of the video framerate conversion. > My solution now is to process the audio externally, in an audio editor. I > must apply a sample rate conversion, first forcing the sample rate metadata > to 50.000 Hz (48.000 *(25/24)) and then resampling at 48.000 Hz > This shortens the audio by the same amount as the video and can be merged > to it. > Is there any way to perform this audio processing within ffmpeg? > Thanks! Have you tried experimenting with the audio filter "atempo"? I'm guessing here, but try: ffmpeg -i ...<your options here> -af atempo=0.96 <outfile> (24/25 = 0.96) ~Steve _______________________________________________ ffmpeg-user mailing list [email protected] http://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email [email protected] with subject "unsubscribe".
