Playing a video by QtMultimedia and gstreamer and its plugin v4l2video9dec0 (VPU hw-accelerated decoding) results in a very slow and stuttering playback for the first ~20 secounds.

Testing the gstreamer path:

$ gst-launch-1.0 playbin uri=file:///tmp/out.avi

 works fine.

So the only difference is the final sink, in QtMultimedia it's qgstvideorenderersink and with gst-launch-1.0 it's kmssink.

So: kmssink is and qgstvideorenderersink is .

By digging a bit deeper, I added some debug calls and timestamps to generate the attached logfile log.txt.

While video is blocked, CPU usage is 0%, when video plays it's ~ 60%

So it seems like a loking issue.

Any ideas?