debugging a/v-sync issues, possibly inter*-element related

Peter K├Ârner osm-lists at
Tue Jun 2 06:30:14 PDT 2015


I'm writing a Videomixer-Application written in python, based on
gsteamer. I'm using an uninstalled git-master build for my tests.

My pipelines look somewhat like this (there are multiple of these
sources and sinks):

Tests revealed, that after 15-30 Minutes of Playback, The output-audio
drifts by 30-50ms with regard to the video (the audio is late wrt. to
the video).

Here is a comparison of a 15 Minute Test-Clip, on the top is the
input, on the bottom the output:
Minute  0:
Minute 20:

The Test-Clip can be found here:

Results vary a little from Machine to Machine and test to test but
they are constant, in that always the audio gets late wrt. the video.

I was able to reproduce the issue with a simple set of pipelines like

although the effect seems to be smaller (I see a drift of 40ms over 30
Minutes) here.

I am ready to spend as much time and effort as needed to debug this
problem, but I get the feeling that simply restructuring the pipelines
and waiting 30 minutes, over and over again, won't help, so I'm asking
you what options I have to debug this further and possibly help fixing it.

My guess is, that there may be a truncation error or sth. the like in
the inter* elements, but I may be wrong here. I'm happy to accept
Ideas on how to debug this further.


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