The reason that the resulting video is longer is simple: it plays slower! which is what you want (pull-down)
By default, ffmpeg does nothing to the audio, so you must stretch it. The most simple solution is to resample it. Try this command line below: the -r before the input tells ffmpeg to interpret the input as 29,97. Assuming that your source audio is at 48.000 Hz, the asetrate sets a "fake" sampling rate to 47952 (stretches the audio longer by the same ratio) and after that aresample resamples back to 48000 Hz. ffmpeg -r 30000/1001 -i input_30fps.mov –i initial_audio.wav -af asetrate=47952,aresample=48000 -c:v rawvideo -c:a pcm_s16le –pix_fmt uyvy422 output_2997fps_withresampledaudio.mov HTH On 13 January 2017 at 03:54, Matthias, Thomas <[email protected]> wrote: > Hi All, > > I need to mux and then framerate convert a rawvideo .mov file, and a PCM > 16bit 48Khz wav file. > > For example, a .mov file is exactly 10 seconds long, and a .wav file is > also exactly 10 seconds. The initial .mov file is a 30 frames-per-second, > but after muxing with the audio, I need to convert it to 29.97. The issue > I’m seeing is that for some reason, the resulting video file is slightly > longer than 10 seconds, and the resulting audio is just shy of 10 seconds. > This leads to the audio being out-of-sync with the video by the end of the > video. In reality, I’m performing this task with much longer clips, and so > the av-sync issue is much more noticeable, but even at 10 seconds the sync > offset is noticeable in a video editor. > > What am I doing wrong? I’ve tried separating the muxing and framerate > conversion into separate FFmpeg calls, but that doesn’t help. I’ve tried > numerous setting combinations, but nothing keeps the audio at the correct > length. I’ve tried using atempo to stretch the audio, but that doesn’t > even seem to work. Here is an example command I’ve tried: > > ffmpeg –y –i initial_video.mov –i initial_audio.wav –c:v rawvideo –c:a > pcm_s16le –pix_fmt uyvy422 –r 30000/1001 output.mov > > I’m clearly missing something here, but I have no idea why the audio track > would end up shorter (in the 10s example, it’s about 9.98 seconds after), > and the video longer (about 10.06). Thanks! > > ~Thomas > _______________________________________________ > 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". _______________________________________________ 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".
