[Matroska-devel] audio async when muxing MP4 files into MKV with mkvtoolnix 2.0.2

Christian HJ Wiesner chris at matroska.org
Mon Feb 26 23:16:19 CET 2007

Moritz Bunkus schrieb:
> Hey,
> On Saturday 24 February 2007 23:05, Christian HJ Wiesner wrote:
>> i am converting MPEG captures from satellite into MP4 files, using VLC
>> 0.86a. Both the MPEG and the MP4 file are perfectly in sync. However,
>> the final MKV, after being muxed from the MP4 with latest mkvtoolnix,
>> will be async. I am not setting any time delays for the audio track, so
>> i wonder why this is ?
>> The delay i have to use to get it into sync is between -200 to -1400 ms
>> for the audio track, meaning the audio is normally too late after
>> muxing.
> I think that the MP4 demuxer in mkvmerge does not handle audio which
> does not start at timecode 0 correctly (meaning the initial delay gets
> lost). Could you upload a test file for me please?

I was trying to, but the logon to your FTP doesn't work ? This is the 
data i was using (from Doom9) :

'If I ever ask you to upload something then please use my FTP server 
(address: mosu.no-ip.com, user: "upload", password: "only").'

Is your FTP down ? Or are there new logon data meanwhile ? Is Port 21 
correct ?

>> Here the warning that mmg is giving me during muxing :
>> ''CTTS' atom is needed for getting the timecodes right. As it is missing
>> the timecodes for this track might be wrong. You should watch the
>> resulting file and make sure that it looks like you expected it to.'
> This is only a problem if the video track contains B frames. If it does
> then the video might stutter. But it has nothing to do with your audio
> delay problem. Mosu

OK. Your first suggestion sounds perfectly like what is happening here. 
Will upload the samples as soon as i get the correct login data.



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