Understanding QOS in gstreamer

[Baby Octopus]

Hi,

I'm running some pipelines to understand QOS. I'm using checksumsink(since
it prints timestamps) which sends QOS events and videoscale which handles
QOS events. And I'm using my PC is intel i3 which can not handle the load.
Here is the pipeline

*gst-launch-1.0 videotestsrc is-live=1 ! videoscale qos=1 !
video/x-raw,width=3840,height=2160 ! checksumsink qos=1 sync=1*
PTS: 0:00:00.271404544  DTS: 0:00:00.271404544
PTS: 0:00:00.304737877  DTS: 0:00:00.304737877
PTS: 0:00:00.571404544  DTS: 0:00:00.571404544
PTS: 0:00:02.304737877  DTS: 0:00:02.304737877
PTS: 0:00:13.971404544  DTS: 0:00:13.971404544

I expected the pipeline to run realtime with frame drops by videoscale. But
this isn't happening. It just hangs

Alternative pipeline with qos=0 at the videoscale runs as expected(Running
slower without dropping any buffers)
*gst-launch-1.0 videotestsrc is-live=1 ! videoscale qos=0 !
video/x-raw,width=3840,height=2160 ! checksumsink qos=1 sync=1*
PTS: 0:00:00.287512027  DTS: 0:00:00.287512027
PTS: 0:00:00.320845360  DTS: 0:00:00.320845360
PTS: 0:00:00.354178693  DTS: 0:00:00.354178693
PTS: 0:00:00.387512027  DTS: 0:00:00.387512027
PTS: 0:00:00.420845360  DTS: 0:00:00.420845360
PTS: 0:00:00.454178693  DTS: 0:00:00.454178693

Am I missing anything here in QOS concept?

~BO



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