So I had this glorious idea of using the CD mp3 instead of the youtube video sound, to have better audio quality. Bad idea.
Audio was slightly faster than video. At first I thought it would be some easy 25-->24 or 24-->23.976 framerate issue, easily fixed with ffmpeg. Bzzt, nope.
Empirical testing with OpenShot (Kdenlive 0.7.6 has some strange bug where clips don't snap to tracks that makes it unusable) showed a relative higher speed of 1.0025 for the audio. That implied that I needed to move from 23.976fps (the original video frame rate) to 24.03594fps. Obviously ffmpeg doesn't support this (better said, the mp4 spec doesn't allow it).
I could apply the 1.0025x in OpenShot quite easily. But, double size video, half the quality, due to this silly thing of fixed output video profiles. Scale-up, whatever, stuff; result: shitty fat video.
In the end, applying the inverse rule in yuvfps (i.e. lying about the source frame rate, which yuvfps swallows be it whatever it be) I got it. The sync is amazingly perfect, so much that I cannot understand where this 1.0025 comes from.
Conclusion: for my next ultrastar adaptation (Fantine's death), which I have already almost finished, I used the youtube audio. Too bad if it's crappy overcompressed, artifact ridden mp3. (It's actually not that bad :P)
Audio was slightly faster than video. At first I thought it would be some easy 25-->24 or 24-->23.976 framerate issue, easily fixed with ffmpeg. Bzzt, nope.
Empirical testing with OpenShot (Kdenlive 0.7.6 has some strange bug where clips don't snap to tracks that makes it unusable) showed a relative higher speed of 1.0025 for the audio. That implied that I needed to move from 23.976fps (the original video frame rate) to 24.03594fps. Obviously ffmpeg doesn't support this (better said, the mp4 spec doesn't allow it).
I could apply the 1.0025x in OpenShot quite easily. But, double size video, half the quality, due to this silly thing of fixed output video profiles. Scale-up, whatever, stuff; result: shitty fat video.
In the end, applying the inverse rule in yuvfps (i.e. lying about the source frame rate, which yuvfps swallows be it whatever it be) I got it. The sync is amazingly perfect, so much that I cannot understand where this 1.0025 comes from.
Conclusion: for my next ultrastar adaptation (Fantine's death), which I have already almost finished, I used the youtube audio. Too bad if it's crappy overcompressed, artifact ridden mp3. (It's actually not that bad :P)
P.s: The final recipe was
ffmpeg -i orig.mp4.bak -f yuv4mpegpipe - | yuvfps -s 2403594:100000 -r 23976:1000 | ffmpeg -f yuv4mpegpipe -i - -y -r 23.976 -b 500k 24.mp4
ffmpeg -i orig.mp4.bak -f yuv4mpegpipe - | yuvfps -s 2403594:100000 -r 23976:1000 | ffmpeg -f yuv4mpegpipe -i - -y -r 23.976 -b 500k 24.mp4
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