> When RTSP server receives a DESCRIBE command, it generates the SDP by parsing 
> the source data. 

This depends upon the particular type of data - but for H.264, that's true, by 
default.


> If description of the source is known, can the SDP can be hard-coded in 
> ServerMediaSession::generateSDPDescription() ?

I presume that you're talking about the "a=fmtp:..." line, because that's the 
part of the SDP description that it makes the most sense to want to 'hard 
code'.  This line is set by the virtual function "auxSDPLine()", which many 
"RTPSink" subclasses redefine, to set this line.

Note, for example, the implementation of this function in "H264VideoRTPSink".  
This implementation sets the "a=fmtp:..." line by reading the SPS and PPS NAL 
units from the upstream 'framer' object, as the input H.264 data is read.  If, 
however, you know this information ahead of time, you could define your own 
subclass of "H264VideoRTPSink" that reimplements "auxSDPLine()" once again.


Ross Finlayson
Live Networks, Inc.
http://www.live555.com/

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