[FFmpeg-devel] [PATCH] Support for Dirac in ogg

David Conrad lessen42
Thu Nov 6 04:27:48 CET 2008

On Nov 5, 2008, at 10:09 PM, Anuradha Suraparaju wrote:

> Hi,
> On Wed, 2008-11-05 at 03:32 -0500, David Conrad wrote:
>> Hi,
>> Attached adds demuxing support for dirac in ogg files. It uses a
>> couple functions for the soc dirac decoder to parse the header,
>> updated to the latest specification.
> In function dirac_header in oggparsedirac.c do you need to parse the
> sequence header? The decoder will do that anyway won't it? If the
> parsing of the sequence header is skipped, then oggparsedirac.c and
> oggdec.c can be merged into the svn trunk straightaway, pending  
> approval
> from the maintainers of course.

The ogg demuxer needs to know the frame rate in order to calculate the  
duration of the stream, which happens before the decoder or parser get  
a chance to do anything.

At any rate I found some subtle issues with dirac's timestamps in ogg  
that prevent going merging. I'll try your improved parser to see if it  
helps. (there are two issues, one being that all ogg dirac sample  
files assume granulepos is the time when the associated packet starts  
rather than the time when it ends as according to the specs. It seems  
the mapping spec also assumes this. The second is that the stored pts  
seems to be plain wrong.)

I'll split the sequence header parsing out since it'd be useful to  
have only one function that's used by your parser as well.

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