How to gurantee lip sync in the multicasting mode

Nicolas Dufresne nicolas.dufresne at
Thu Oct 4 08:06:08 PDT 2012

Le mercredi 03 octobre 2012 à 13:33 -0700, Nathan a écrit :
> Hi Nicolas,
> I also tried to put the "sync" of udpsrc or rtpsrc of the receiver to be
> ture, but that will make the received video very non-smooth.  It seems that
> this property has to be FALSE. 

SRC elements don't have this parameter. To have synchronisation, you
must have those to TRUE on the audio and video SINK elements on the
receiver side. For sure, video won't be smooth if your network (combine
with encoding parameters) cause more latency then what is being
configured. (note, I have no idea what you are referring to for rtpsrc)

> Here is our other setting related to the gsteamer, I really am in the dark.
> Hope someone can point me out some directions regarding the lipsyn in the
> multicasting mode:
> Tx:
> Rx:
> g_object_set(G_OBJECT(rtpbin), "latency", 200, "buffer-mode", 0, "ntp-sync",
> TRUE, "use-pipeline-clock", TRUE, NULL);

You can try increasing the latency parameter, the rest seems to depend
on your use case, and on how the sender side is implemented. Normally,
200ms shall be sufficient, but that depends on many factor, and the
quality you want to achieve. You should consider having a second look at
how you are encoding your video. If you are using a public encoder, you
could expose the settings you use here.


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