[Live-devel] Adding streams to already-running event loop

[Ross Finlayson]

First you need to figure out exactly when/how you’re going to decide when to add a new stream.  I.e., you need to figure out what event will cause this to happen.

If it’s simply a delayed task - within the event loop (i.e., set up using “TaskScheduler::scheduleDelayedTask()”) - then you don’t need ‘event triggers’ at all.  Instead, simply add the new stream from the ‘delayed task’.  Ditto if the event occurs as a result of reading data from a socket.


If, however, you decide to do this from some external thread (i.e., from the thread that is *not* running the LIVE555 event loop), then you can call “triggerEvent()” from this external thread.  Note that “triggerEvent()” is the *only* LIVE555 code that you may call from this external thread; all other LIVE555 calls *must* be done from within the ‘LIVE555 event loop’ thread.

If you decide to use ‘event triggers’ (triggered from an external thread), then you are sort of on the right track, with a couple of corrections:

> myRTSPClient::createNew(env,url,etc.){
>    …
>    addStreamEventTriggerId = envir().taskScheduler().createEventTrigger(addStreamToLoop);

Note that the function parameter to “createEventTrigger()” has to have the proper “TaskFunc” signature:
	typedef void TaskFunc(void* clientData);


> myClient =  myRTSPClient::createNew(env, url, etc.);
> ourScheduler->triggerEvent(myRTSPClient::addStreamEventTriggerId, myClient);

Because you are calling “triggerEvent()” from an external thread (again, if you’re in the LIVE555 event loop thread when you decide to create a new stream, then you don’t need event triggers at all), you can’t call “myRTSPClient::createNew()” from within that thread.  Instead, the “myRTSPClient::createNew()” call should occur (along with a subsequent “sendDescribeCommand()”) within the event handler function - i.e., within the LIVE555 event loop.

So, to get this, you can do something like:

///// Within the LIVE555 thread:

void newStreamHandler(void* clientData) {
	char* url = (char*)clientData;
	myRTSPClient* myClient =  myRTSPClient::createNew(env, url, etc.);
	myClient->addStreamToLoop();
}

TaskScheduler* live555TaskScheduler = &(envir().taskScheduler()); // A global variable
EventTriggerId newStreamEventTrigger =  envir().taskScheduler().createEventTrigger(newStreamHandler); // A global variable
	// Note that you need to create only one event trigger

envir().taskScheduler().doEventLoop(); // does not return

///// Then later, within a separate thread:

live555TaskScheduler->triggerEvent(newStreamEventTrigger, url_for_the_new_stream);


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