Latency compensation

[Nicolas Dufresne]

Le mercredi 12 décembre 2018 à 20:38 +0100, Wolfgang Grandegger a
écrit :
> Hello,
> 
> I'm trying to understand how the processing latency is compensated for
> the simple pipeline:
> 
>   $ gst-launch-1.0 -v udpsrc port=50004 buffer-size=180000000 \
>     caps="application/x-rtp, media=(string)video, clock-rate=(int)90000,
>     encoding-name=(string)JPEG, payload=(int)26,framerate(fraction)60/1" \
>     ! rtpjitterbuffer latency=0
>     ! rtpjpegdepay 
>     ! vaapijpegdec
>     ! vaapisink 
> 
> GST_TRACERS="latency" reports the following latency from the src to the sink:
> 
>   61495822
>   61865042
>   61219613
>   61537702
> 
> If I use "sync=false" on the "vaapisink", I see that the latency is just 2ms.
> There is some latency adoption taking place? How does it work? How can I
> change it?

We are still working on improving the latency tracer, which version of
GStreamer are you running with ?

Note that the latency reported by the latency if the effective latency.
So it's a combination of the processing and the buffering latency. With
udpsrc, depending on which start time has been decided and how much
latency is declared by each element, you'll always get some more
latency then when disabling sink, which will keep the queues low, but
with a bursty rendering, and not all image might reach the screen.

> 
> Wolfgang.
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