Streaming freezes (vaapi or v4l2src)

[Timtchenko, Michael]

Hello guys,

i've encountered a very strange behavior while streaming from a v4l2src to a kmssink (or glimagesink) by using vaapi-components for decoding. The problem is, that the streaming starts for 2 seconds, then freezes for 2 seconds and continues again for 2 seconds and so on. This effect is only noticeable when using vaapi-components. If I use a pipeline with simply software decoding, the stream is displayed fluently.

My sending pipeline is constructed as follows:

gst-launch-1.0 v4l2src io-mode=dmabuf device=/dev/video$(($1+4)) ! video/x-raw,format=YV12,width=720,height=576  ! v4l2h264enc ! rtph264pay ! udpsink host=${IP} port=55555

Setting pipeline to PAUSED ...
Pipeline is live and does not need PREROLL ...
Setting pipeline to PLAYING ...
New clock: GstSystemClock
Redistribute latency...

The erroneous reading pipeline looks like this:

gst-launch-1.0 udpsrc port=55555 caps="application/x-rtp,media=(string)video,clock-rate=(int)90000, encoding-name=(string)H264, payload=(int)96" ! rtph264depay ! vaapih264dec ! vaapipostproc width=720 height=576 ! glimagesink

Setting pipeline to PAUSED ...
Pipeline is live and does not need PREROLL ...
Got context from element 'vaapipostproc0': gst.vaapi.Display=context, gst.vaapi.Display=(GstVaapiDisplay)"\(GstVaapiDisplayDRM\)\ vaapidisplaydrm1";
Setting pipeline to PLAYING ...
New clock: GstSystemClock
Redistribute latency...
WARNING: from element /GstPipeline:pipeline0/GstKMSSink:kmssink0: A lot of buffers are being dropped.
Additional debug info:
../libs/gst/base/gstbasesink.c(3005): gst_base_sink_is_too_late (): /GstPipeline:pipeline0/GstKMSSink:kmssink0:
There may be a timestamping problem, or this computer is too slow.
WARNING: from element /GstPipeline:pipeline0/GstKMSSink:kmssink0: A lot of buffers are being dropped.
Additional debug info:
../libs/gst/base/gstbasesink.c(3005): gst_base_sink_is_too_late (): /GstPipeline:pipeline0/GstKMSSink:kmssink0:
There may be a timestamping problem, or this computer is too slow.

If I run the following pipeline on the same system, the stream is presented fluently without any problems:

gst-launch-1. 0 udpsrc port=55555 caps=\"application/x-rtp, media=(string)video, clock-rate=(int)90000, encoding-name=(string)H264, payload=(int)96\" ! rtph264depay ! avdec_h264 ! decodebin ! videoconvert ! kmssink

I'm not sure what exactly the problem is. Maybe the timestamping mechanism in vaapi has a different behavior then in the avdec_h264 as the log message says?  I've also changed log levels but I couldn't find anything helpful.

Any help for further diagnostics is highly appreciated.

Kind regards
Michael





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