[openbeos] Re: Solution to MediaKit sync issue resolved
- From: "Solaja, Zenja" <solaja@xxxxxxxxxx>
- To: openbeos@xxxxxxxxxxxxx
- Date: Wed, 30 Jun 2004 10:11:51 +1000
It seems that the issue is with decoding a BMediaTrack, and its method
DecodedFormat(). When you perform a SeekToTime(bigtime_t), it misjumps by a
factor of 1024/1000. Also, the DecodReadFrame or ReadChunk() members of
BMediaTrack will as a consequence read 1024/1000 bytes when passing it to
BSoundPlayer. To resolve audio sync issues, all you need to do is manually
adjust bigtime_t when seeking by:
time *= 1000/1024;
SeekToTime(time);
Its the decoders responisbility to resolve variable bit rate issues - higher
level code doesn't need to know (and doesn't care). I haven't noticed an
issue, so I'm assuming that its OK.
Also, when setting up DecodedFormat(format), adjust the frame rate by
1000/1024, and you should bypass the synchronisation issues. Hopefully, the
Haiku MediaKit will not have this bug.
PS.David, I've never had an issue with the video portion of 3ivx (hey,its my
favourite decoder). Appretiate your work on it :-)
-----Original Message-----
From: David McPaul [mailto:dmcpaul@xxxxxxxxxxxxxx]
Sent: Tuesday, 29 June 2004 5:46 PM
To: openbeos@xxxxxxxxxxxxx
Subject: [openbeos] Re: Solution to MediaKit sync issue resolved
Zenja,
Have you tested this with an AVI containing a Variable Bit Rate
MP3?
I can see how the problem discussed below can cause the problem
which suggests that some/all? of the media decoders are using 1024 as
the time divider in places or do you think it is at the media player
code?
I think most problems people have with AVI (where the problem is
often reported) is because the MP3 audio they use is VBR and so it can
be difficult to seek correctly. Simply because 10 frames of VBR audio
will vary depending on where you are in the track.
The other issue is simply that the recorded audio simply cannot be
syncronised with the video as the frame rate of each track is too
different.
For the record the 3ivx decoder uses 1000 as a base when seeking by
time.
Cheers
David
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