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

[Peter Körner]

Hi Nicolas,

On 03.06.2015 02:45, Nicolas Dufresne wrote:
> Le Tuesday 02 June 2015 à 15:30 +0200, Peter Körner a écrit :
>> 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.
> 
> The inter sink/src element are use to split your stream into multiple
> pipeline. This means, split your stream over multiple clocks, hence not
> synchronization is happening.
I chose that design with inter-Elements so that when a source dies
(someone pulls a plug, for example), the mixer- and output-pipelines
keep running. inter*src fills the gap with black/silence in this case.

Is there another design that would achieve this?


> If you want synchronized playback, keep
> everything in the same pipeline, or considering using a shared clock.
I was under the impression that they would share the same
Gst.SystemClock anyway.

Nevertheless I created a global Gst.SystemClock and shared them across
all pipelines. I set start_time to CLOCK_TIME_NONE and base_time to a
common value fetched from the clock upon startup, following the example
<http://noraisin.net/gst/play-master.py>

The result is identical: the audio starts 10ms early on the output,
drifts to beeing equal and drifts on to 30ms late over ~30 minutes playback.

I tested with this example which is self contained, in that it does only
use gstreamer elements to reproduce the issue:

<https://github.com/voc/voctomix/blob/c92b03943beeec94fab5afd68f22a5c0d249d7ab/voctocore/experiments/avsync-fileio-clock.py>


Regards, Peter

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