[Live-devel] Payload attributes

[Ross Finlayson]

> I have already created my own ServerMediaSubsession subclasses for my application.  One for PCM and one for MP3.  By doing this, the listener is able to see if it is receiving a PCM stream or a MP3 stream and play it correctly.  The problem however is that I need to send attributes along, for example the bits, frequency and channels of the PCM sample so that the listener knows how to play it.  The bits, frequency and channels can be changed on the streamer side and this is the information that I want in the SDPDescription or any other appropriate place.

The sampling frequency and number of channels will sometimes appear in the SDP description (in the a=rtpmap: line), if the RTP payload type is dynamic.  If the RTP payload type is static, however, then these parameters are implied.  For example, payload type 10 is defined to mean 44100 Hz 2-channel PCM (16-bit) audio.

I agree, however, that this won't be enough for you, because you want this information to always appear explicitly in the SDP description.  What you can do, however, is create a string - describing the stream's parameters - and pass it as either the "info" or the "description" parameter to "ServerMediaSession::createNew()".  Then, this string will automatically appear in the SDP description, as the "i=" or the "s=" line, respectively.


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

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