[Live-devel] File handle leak in slightly modified testMPEG2TransportStreamer

[Ross Finlayson]

> Given that, why doesn't the sink take full ownership of the source object once you pass it to startPlaying()?

Because it doesn't :-)  That design decision was made (I think; it's been well over a decade now) because 'sources' and 'sinks' are different kinds of object.  In principle, many different objects - not just a 'sink' - may want to perform some operation (other than 'playing') on a 'source'.  And because the 'source' and 'sink' were each created by a third party (the "testMPEG2TransportStreamer" application code, in this case), it makes sense for the same third party to take responsibility for reclaiming the 'source' and 'sink' objects, when it wants to do so.

(OTOH, "FramedFilter" objects (a subclass of "FramedSource") *do* take ownership of their upstream input source object; that's why you can delete an entire filter chain by deleting just the tail "FramedFilter" object ("videoSource" in this case).)

Anyway, the way to avoid global variables in (your modified) "testMPEG2TransportStreamer" application is to use the 'clientData' parameter in the 'afterPlaying' callback.  E.g., you can do something like:

	struct streamParameters {
		FramedSource* source;
		MediaSink* sink;
		// any other stream-specific parameters that you want
	};

and then:

	streamParameters* myStream = new streamParameters;
	myStream->source = videoSource;
	myStream->sink = videoSink;

	videoSink<-startPlaying(*videoSource, afterPlaying, myStream); // note: The last parameter to "startPlaying()" is different than before

and then, in "afterPlaying()":

	void afterPlaying(void* clientData) {
		streamParameters* myStream = (streamParameters*)clientData;
		myStream->sink->stopPlaying();
		Medium::close(myStream->source);

		play();
	}

Voila!  No global variables.

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

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