[FFmpeg-soc] [PATCH] xiph packetizer

[Josh Allmann]

On 5 August 2010 01:44, Martin Storsjö <martin at martin.st> wrote:
> On Thu, 5 Aug 2010, Josh Allmann wrote:
>> >> -#define SDP_MAX_SIZE 8192
>> >> +#define SDP_MAX_SIZE 16384
>> >>
>> >
>> > Is there any limit on the size of the extradata for theora/vorbis?
>> > Can we be reasonably sure this is enough for at least one theora stream
>> > plus one vorbis stream?
>> >
>>
>> I am assuming you mean one theora stream, OR one vorbis stream, not
>> AND. sdp_parse in rtsp.c (line 397) claims 16KB max for the FMTP line,
>> but I'm not sure what the provenance of that number is. I took a quick
>> glance through the Theora and Vorbis bitstream specs, and couldn't
>> find any hard figures for this. From empirical testing, the Theora
>> extradata is usually a bit smaller than the Vorbis. Even then, I have
>> yet to see (non-base64-encoded) sizes of more than 5KB. So we should
>> be comfortably under this limit.
>
> No, I ment AND - if you stream both and audio video, the description of
> both go into the same single SDP block, so it has to be large enough for
> both of them. The comment at line 397 in rtsp.c refers to one single SDP
> line, so if there are cases where a vorbis line actually could be almost
> 16 KB, we'd need yet a bit more space if we'd want to stream theora at the
> same time.
>

I have yet to see a theora+vorbis stream take more than ~14KB of sdp.
If we encounter a sample that takes up more, we can enlarge the buffer
then.

Josh