Using gst-launch with ximagesrc says "There may be a timestamping problem, or this computer is too slow." - how do I solve this?

Mon Apr 6 16:26:24 UTC 2020

Hi,

On Sun, 2020-04-05 at 01:20 +0100, Alain Culos wrote:
> Dear All,
> 
> I just discovered GStreamer, so apologies if this is a basic error, but no matter how hard I try I can't find what is wrong with my set-up / pipeline.
> 
> ===========
> Summary:
> When using ximagesrc, error messages appear to tell me buffers are lost and that there may be timestamping issues or that my computer is slow.

Have you tried using "use-damage=false" parameter on ximagesrc?

> 
> I have a beefy desktop, 1yo i7, 6-core hyperthreaded, 64GB RAM ubuntu 18.04).
> GStreamer 1.14.5
> 
> ===========
> In detail:
> 
> The video shown with this command line is very laggy (it hardly uses any RAM or CPU // other note: my desktop easily copes with e.g. zoom meetings):
> 
>     gst-launch-1.0 autovideosrc ! videoconvert ! autovideosink # shows no error message
>     gst-launch-1.0 v4l2src device=/dev/video0 ! videoconvert ! autovideosink # does exactly the same
> 
> 
> Preparing the ground for chroma-keying a green screen background, this example works the same way the first two do (laggy but good quality & no error message showing):
>     w=1280; h=800; x0=450; y0=200; gst-launch-1.0 \
>         v4l2src device=/dev/video0 \
>         ! videocrop left=$x0 right=$(( 1920 - $w - $x0 )) top=$y0 bottom=$(( 1080 - $h - $y0 )) \
>         ! alpha method=green angle=70 \
>         ! videoconvert \
>         ! autovideosink
> 
> The background to replace the green screen will be taken from an application window.
> This causes issues with buffers dropped & it complains about timestamping issues.
>     gst-launch-1.0   ximagesrc xid=0x02a00006 ! videoconvert ! autovideosink
> 
> Below is the output of the command above:
>     Setting pipeline to PAUSED ...
>     Pipeline is live and does not need PREROLL ...
>     Setting pipeline to PLAYING ...
>     New clock: GstSystemClock
>     WARNING: from element /GstPipeline:pipeline0/GstAutoVideoSink:autovideosink0/GstXvImageSink:autovideosink0-actual-sink-xvimage: A lot of buffers are being dropped.
>     Additional debug info:
>     gstbasesink.c(2902): gst_base_sink_is_too_late (): /GstPipeline:pipeline0/GstAutoVideoSink:autovideosink0/GstXvImageSink:autovideosink0-actual-sink-xvimage:
>     There may be a timestamping problem, or this computer is too slow.
> 
> 
> Even if I impose a low frame rate, it outputs the same error messages as above, command line:
>     gst-launch-1.0   ximagesrc xid=0x02a00006 ! video/x-raw,framerate=5/1 ! videoconvert ! autovideosink
> 
> Obviously, if I combine the two, performance gets worse, despite still not hitting the CPU or RAM, and the following command shows exactly the same messages as above:
>     w=1280; h=800; x0=450; y0=200; gst-launch-1.0   \
>         v4l2src device=/dev/video0 \
>         ! videocrop left=$x0 right=$(( 1920 - $w - $x0 )) top=$y0 bottom=$(( 1080 - $h - $y0 )) \
>         ! alpha method=green angle=70 \
>         ! mixer.sink_1   \
>         \
>         ximagesrc xid=0x02a00006 ! videoscale \
>         ! video/x-raw,width=$w,height=$h ! mixer.sink_0   \
>         \
>         videomixer name=mixer sink_0::zorder=0 sink_1::zorder=1 \
>         ! videoconvert ! autovideosink
> 
> Whether I put ximagesrc before v4l2src or after changes nothing.
> 
> (next challenges: 1/ channelling this to /dev/video10; 2/ channeling the audio from the webcam (/dev/video0) to the virtual webcam (dev/video10))
> 
> For now I  would most appreciate some help with making the above commands works without error/warning messages and good performance. Or in other words how do I resolve timestamping with ximagesrc?
> 
> Best regards,
> Alain.
> 
> 
> On Wed, 1 Apr 2020, at 02:42, Alain Culos wrote:
> > Hi,
> > 
> > I am a recent newcomer to gstreamer.
> > Trying to use `gst-launch-1.0` to chroma-key my webcam and insert a pdf 
> > as background.
> > 
> > My attempt is very imperfect:
> > 1/ I have not been able to find the right parameters to make the window 
> > sizes match.
> > 2/ gst-launch occasionally complains it loses a lot of buffers.
> > 3/ the video output only updates seemingly randomly, infrequently, and 
> > seems to (but not always) needs the pdf window to have focus and the 
> > mouse to be over it (but not exclusively).
> > 
> > Maybe there is a better solution.
> > My desktop is quite powerful: a modern (about 1yo, i7, 6-core, 
> > hyperthreaded, 64GB RAM), 4k display, 1080p USB webcam, SSD.
> > Linux 5.3.0-40-generic #32~18.04.1-Ubuntu SMP Mon Feb 3 14:05:59 UTC 
> > 2020 x86_64 x86_64 x86_64 GNU/Linux
> > ()
> > 
> > The commands I ran are:
> > 
> > 1/ testing the chroma-key with a chequered background
> > gst-launch-1.0 \
> >   videotestsrc pattern=checkers-8 ! video/x-raw,width=800,height=640 ! 
> > mixer.sink_0 \
> >   autovideosrc ! video/x-raw,width=800 ! alpha method=custom 
> > target-r=255 target-g=255 target-b=255 ! mixer.sink_1 \
> >   videomixer name=mixer sink_0::zorder=0 sink_1::zorder=1 ! 
> > videoconvert ! autovideosink
> > -> Very slow video, does not chroma-key on white!
> > gst-launch recurrent message: "A lot of buffers are being dropped"
> > 
> > 2/ testing the chroma-key (2nd attempt)
> > gst-launch-1.0 \
> >   videotestsrc pattern=checkers-8 ! 
> > video/x-raw,width=800,height=640,framerate=1/1 ! mixer.sink_0 \
> >   autovideosrc ! video/x-raw,width=800 ! alpha method=custom 
> > target-r=255 target-g=255 target-b=255 ! mixer.sink_1 \
> >   videomixer name=mixer sink_0::zorder=0 sink_1::zorder=1 ! 
> > videoconvert ! autovideosink
> > -> Same as above
> > 
> > 3/ testing my video
> > gst-launch-1.0 autovideosrc ! video/x-raw,width=800 ! videoconvert ! 
> > autovideosink
> > -> Showing my webcam is almost real-time, but has a bit of lag
> > The same test at 1080p is very laggy
> > 
> > 4/ testing a source application window (evince, showing a pdf file)
> > gst-launch-1.0 \
> >   ximagesrc xid=0x06800008 ! mixer.sink_0 \
> >   autovideosrc ! video/x-raw,width=800 ! alpha method=custom 
> > target-r=255 target-g=255 target-b=255 ! mixer.sink_1 \
> >   videomixer name=mixer sink_0::zorder=0 sink_1::zorder=1 ! 
> > videoconvert ! autovideosink
> > -> Does not update the video in realtime (only updates rarely, at most 
> > every few seconds, when the application window has the focus or redraw 
> > events (possibly and/or mouse over)), does not allow me to resize the 
> > application window video stream.
> > 
> > 
> > Hoping to find here some pointers to solve the issues highlighted 
> > above, most importantly performance (framerate).
> > 
> > Next steps: a/ including the audio stream, b/ outputting to a video 
> > device so I can use this as a source for a video conference 
> > (zoom/skype/jitsi), c/ using an actual green screen.
> > 
> > Thanks for any help, pointers to documentation or tutorials.
> > Regards,
> > Alain.
> > _______________________________________________
> > gstreamer-devel mailing list
> > gstreamer-devel at lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/gstreamer-devel
> > 
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