Hello Ross and everyone
I never got to thank you for fixing the race condition in
H264VideoFileServerMediaSubsession and MPEG4VideoFileServerMediaSubsession
(release
2011.06.14) so, thank you very much for that one.
I believe I came across another bug.
We are running an application in which we create 3 replicas (thank you also for
the StreamReplicator) from each live source: one for multicast
streaming, one for unicast streaming and another for video file storing.
Soon after we started using the StreamReplicator we noticed that frequently,
when a unicast client closed a session, the whole pipeline
stopped.
After some debugging I came across the following lines of code which I changed
as you can see:
============
--- live-2012.04.27/liveMedia/StreamReplicator.cpp 2012-04-27
20:53:46.000000000 +0100
+++ live-new/liveMedia/StreamReplicator.cpp 2012-04-30 19:25:15.000000000 +0100
@@ -143,16 +143,16 @@
}
} else {
// The replica that's being removed was not our 'master replica', but make
sure it's not on any of our queues:
- for (StreamReplica*& r1 = fReplicasAwaitingCurrentFrame; r1 != NULL; r1 =
r1->fNext) {
- if (r1 == replicaBeingDeactivated) {
- r1 = replicaBeingDeactivated->fNext;
+ for (StreamReplica** r1 = &fReplicasAwaitingCurrentFrame; (*r1) != NULL;
r1 = &((*r1)->fNext)) {
+ if ((*r1) == replicaBeingDeactivated) {
+ (*r1) = replicaBeingDeactivated->fNext;
replicaBeingDeactivated->fNext = NULL;
break;
}
}
- for (StreamReplica*& r2 = fReplicasAwaitingNextFrame; r2 != NULL; r2 =
r2->fNext) {
- if (r2 == replicaBeingDeactivated) {
- r2 = replicaBeingDeactivated->fNext;
+ for (StreamReplica** r2 = &fReplicasAwaitingNextFrame; (*r2) != NULL; r2 =
&((*r2)->fNext)) {
+ if ((*r2) == replicaBeingDeactivated) {
+ (*r2) = replicaBeingDeactivated->fNext;
replicaBeingDeactivated->fNext = NULL;
break;
}
============
By using a reference, it's always the head of the list that's updated which, I
believe, is not what was meant. If there is (as it happens in
our case) more than one replica waiting on a frame and the replica being
deactivated in not the first on that list, the replicas in front of
the list are lost.
Now I'm guessing a bit but I believe that then, when the frame finally arrives,
the master replica will wait forever for the other replicas to
ask for the current frame when, in fact, they already did (hence the pipeline
halt).
Using the patch above did, at least, fix the symptoms. I don't think all the
parentheses I've used are necessary but I like to use them for
safety.
Thanks in advance for any enlightenment or new release that may fix this issue.
Bruno Abreu
--
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