[FFmpeg-user] mpeg-ts to mkv without sound delay
pbasista at gmail.com
Sat May 21 17:07:11 CEST 2011
> Hi everyone,
> I wood like to change the container of some videos I record with my TV, and
> compress it for archiving purpose.
> The container is mpeg-ts, the video codec is h264 and the audio one is mp2.
> I wood like mkv, h264, aac. I also want the video stream to be more
We seem to have similar goals :)
> So the first step is to change the container, I try :
> ffmpeg -i test.ts -vcodec copy -acodec copy movie.mkv
> The process run normally except this message :
> [NULL @ 0x645bb0]missing picture in access unit
> The output file is fine but there is a delay between sound and video.
Can you be more specific? If I do the same thing with my captured
mpeg-ts file, I have no delay at all. Only for the first a few seconds
after the playback starts, there is an audio delay, but it is
continuously fading away and after about 10 seconds, everything is in
A piece from mplayer's status line:
A: 1.9 V: 3.4 A-V: -1.534
That is, I suppose, mplayer's issue. It is just not able to sync audio
and video from this file immediately after the start of the playback.
But then it all plays in sync. I don't think the reason is that the
audio and video are not synchronized in the resulting file.
> So my questions are :
> 1. How to avoid this delay ?
Explain in more detail what kind of delay you experience.
> 2. How to compress more the video stream ? Maybe try with a
> different bitrate ? Is there a way to automatically choose a suitable
I do not have any bright ideas about that. However, since the source
is h264, I would try very hard to avoid reencoding, unless it is
absolutely necessary. I don't know how much you care about the
resulting file size, but I doubt that you can achieve significant file
size reduction (say, 50%) while maintaining the video quality. On the
other hand, I may be wrong. I am no expert in this field.
Another question is whether it is worth to reencode the video if you
know that it will reduce its size only by, say 20%. Would you sitll
want to do it? Most of the time, I would not.
> 3. To change the audio codec -acodec aac will be ok ?
This will only work if you add -strict experimental to your command
line. I do not have any experience with that, but you can also use the
non experimental codec libfaac.
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