30 October

I recently used MythTV to record some video acquired by an HDHomeRun box from Silicon Dust. The video files recorded by MythTV cannot be played, in many cases, by other video players, not even the superb VLC. This seems to be a results of dropped video frames (which in my case might be because I made the recording over a wireless network). Other people have also reported the same problem. Dropped frames are likely with video that comes over the air (ATSC) or satellite as well.

One partial solution is to re-encode the video using the open-source ffmeg program. Unfortunately, when you do this although the video becomes playable it is likely to lose audio sync. You can see the video and hear the audio, but the audio is no longer properly synchronized with the picture, due to the occasional dropped frame.

Well, it turns you this can be fixed using extra flags to ffmpeg. Specially, the -async flag can fix the problem. My preferred solution, for extra robustness, is to use:

-async 4 -vsync 5

Thus, you can transcode the video (assuming it was named 3442_20101030195200.mpg, with the command:

ffmpeg -i 3442_20101030195200.mpeg -sameq
-async 4 -vsync 5 3442_20101030195200.mp4

I hope this helps somebody. I saw several pleas on the net for solutions to this problem.

By Gregory Dudek at | Leave a comment |    
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