[FFmpeg-devel] [PATCH] Add the frame size attribute to SDP descriptions

Luca Abeni lucabe72
Fri Jan 8 09:10:57 CET 2010

Hi Martin,

Martin Storsj? wrote:
> On Thu, 7 Jan 2010, Luca Abeni wrote:
>> Good, thanks. If you find this attribute described in some standard, or if you
>> find some commonly used RTP client which needs it for some reason, I'll be
>> happy to commit the patch.
> Ah, here it is:
> http://tools.ietf.org/html/draft-westerlund-mmusic-3gpp-sdp-rtsp-07#section-4.2

Ah, ok... Thanks for the search. So, it is a 3GPP thing...
I am ok for supporting "a=framesize". However, the specified size
should be "the largest picture size a specific H.263 payload type
will carry within the session". So, using c->width and c->height
is not entirely correct.

I think we have 2 possibilities:
1) Applying your patch, with a comment saying where this attribute
    comes from, and clarifying that this setting might be incorrect
    if the video size changes
2) Not using c->{width,height}, but using the AVMetadata
    infrastructure... This might be a little bit more complex, but
    I believe it is more flexible, allowing the user to add more "a="
    lines if needed (without needing to modify sdp.c every time).
    My basic idea is that if the AVFormatContext contains a metadata
    tag with key "key" and value "value", then the "a=key:value" line
    is added to the SDP (the "title" metadata should be excluded
    because it is already used for the "s=" line).

What do you think?


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