When watching videos on a 3rd generation iPod Nano, maybe 10% of all videos, specifically around 12 minutes, either stop (the video player exits back to the list of videos), or video and audio gets out of sync (video skips ahead up to 10 minutes, while the audio keeps playing where it's supposed to).
Interestingly, videos that fail on the iPod Nano also fail in iTunes and QuickTime on the Mac, but in different places. One video plays fine in QuickTime until 3:45, after which video fails to play while audio plays fine. At this point, pausing QuickTime causes VTDecoderXPCService to use max CPU.
Some additional details:
- The video plays fine in VLC or mplayer on the Mac
- The problem persists if I remove the audio track (
My best guess is that a particular encoding scheme must be enforced for Apple-specific video players. Can anyone explain the phenomenon and suggest a cure?
This is the conversion method I'm using:
ffmpeg in.mp4 -vcodec libx264 -acodec aac -ac 2 -ar 44100 -ab 128k -profile:v baseline -level 3.0 -pix_fmt yuv420p -vf scale=320:240 out.mp4
Update: FFmpeg lists the input videos as having framerate
23.98 fps, 23.98 tbr, 23.98 tbn, 23.98 tbc. Explicitly adding
-r 23.98 as output parameter gives
23.98 fps, 19184 tbn, 23.98 tbc for the output file, and makes the video work. So, omitting
-r fails, while setting
-r for the output file identical to the framerate of the input file works.
Can someone enlighten me as to what kind of a strange quirk this is?