[Live-devel] Rare 2s "delay" when viewing live streams

[Erlandsson, Claes P (CERLANDS)]

We stream lots of live MJPEG streams using a pretty simple client that is
based on the testRTSPClient example. In very rare cases we see a delay/lag
that I can't explain.

 

When it happens it is like the live video is delayed 2s. If I at the time
start the same stream in VLC and specify a cache of 2000ms the videos play
in sync.

 

The thing is that we don't buffer anything, and the fact that any other
instance of our program, or any other player, shows the video live tells me
it's not the server. The instance where the delay can be seen will continue
to do show the delay for all following streams (using the same live555 event
loop), i.e. if I switch to another stream the delay is still there. It
should be noted that the video plays smooth (no visible frame dropping),
just that there is a consistent 2s lag. As mentioned, this is very rare and
I've only seen it twice in the last four months, so it's not something that
I can recreate.

 

 

I didn't think live555 really buffer anything, but when trying to look for
any explanation at all to this "magic delay" I stumbled upon some old posts
that mention a buffer used for sorting RTP packages that are received out of
order. It also mentions that setPacketReorderingThresholdTime() can be
called to minimize this time. I believe we have quite a bit of packet loss
and I will try to check this out, but since we can't reproduce the issue
it's like a ghost hunt and it would be great to get some feedback on this.

 

 

- Is there any possibility that a "delay" (>1s) can somehow be introduced in
live555 (e.g. during heavy packet loss)?

 

- Has anyone else experienced any delayed live streams like this?

 

 

/Claes

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