[Live-devel] Subclassing OnDemandServerMediaSubsession for Live Video Sources to stream h264

[Ross Finlayson]

> I am using Live555 library to create rtsp stream for live device source. I read the FAQ and mailing list and sub classed all the required classes ::
> 1.       Framed source (using the deviceSource.cpp model)
> 2.       OnDemandServerMediaSubsession (using H264VideoFileServerMediaSubsession model)
> But few on the questions are I am not able to figure out:
> 1.       In each call of my doGetNextFrame() of my device source I am assuming that no frame data is available and I am returning. Instead whenever I receive data I trigger a event which schedule getNextFrame() of my device source. Is there is status check (waiting for event or running) required for Live555 run loop  to schedule the task of the new data arrival in the function signalNewFrameData() of device source?

The LIVE555 event loop (which you entered when you ran "doEventLoop()") automatically figures out when "TaskScheduler::triggerEvent()" has been called (from another thread), and calls the appropriate handler function (which you registered when you called "createEventTrigger()"; i.e., the "deliverFrame0()" function in the "DeviceSource" example code).


> 2.       In my OnDemandServerMediaSubsession subclass I have implemented both required function createNewStreamSource() and createNewRTPSink(). Since I set the reuseFirstSource to true in my OnDemandServerMediaSunsession I keep a reference of my device source in my dataMember variable.

That's your problem.  Setting "reuseFirstSource" to True simply means that only one instance of the source class will be created *at a time*, regardless of the number of concurrent RTSP clients that have requested the stream.  It does *not* mean that only one instance of the source class will be created *ever*.  In fact, as you noticed, the "OnDemandServerMediaSubsession" code creates an initial instance of the source class (it uses this to generate the SDP description in response to the first RTSP "DESCRIBE").  It then closes this object.  Later, when the first RTSP client does a RTSP "SETUP", another instance of the source class will be created.  (That instance will not get closed again until the last concurrent client does a "TEARDOWN".)

So, your code should allow for the possibility of more than one instance of your data source class being instantiated (and later closed) - but sequentially, not concurrently.  DO NOT modify the supplied "OnDemandServerMediaSubsession" source code.

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

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