[Live-devel] Possible missing parameter in MPEG4ESVideoRTPSink::auxSDPLine()

[Ross Finlayson]

The problem with MPEG-4 (and H.264) video is that - to properly serve the stream - you need (in the stream's SDP description) certain 'configuration' parameters.  Often, these configuration parameters can be obtained only by reading the stream itself.  In this case, we have a 'chicken and egg' problem: Parameters that are needed to serve the stream can be obtained only by first reading the stream.

To solve this, note how in "MPEG4VideoFileServerMediaSubsession" (a subclass of "OnDemandServerMediaSubsession") we reimplement the virtual function "getAuxSDPLine()".  If you *don't* know - in advance - the configuration parameters for the stream, then you will need to also reimplement "getAuxSDPLine()", and do something similar, in your own subclass of "OnDemandServerMediaSubsession".

If, however, you *do* know - in advance - the configuration parameters for the stream, then there is an alternative solution:
Recent versions of the code (>= version 2012.03.20) have an alternative version of "MPEG4ESVideoRTPSink::createNew()" that take the configuration parameters as arguments.  Specifically, it takes two extra arguments:
	u_int8_t profileAndLevelIndication, char const* configStr
If you know this information in advance, then you should use this new version of "MPEG4ESVideoRTPSink::createNew()" in your reimplementation of the "createNewRTPSink()" virtual function, and you then *do not* need to reimplement "getAuxSDPLine()".


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

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