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

Alain Culos gstreamer at asoundmove.net
Mon Apr 6 19:39:19 UTC 2020 

Thanks for this tip,

On Mon, 6 Apr 2020, at 17:26, Desouza, Ederson wrote:
> 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 had not, I now have.

    gst-launch-1.0   ximagesrc xid=0x02a00006 use-damage=false ! videoconvert ! autovideosink

The simple pipeline above now works flawlessly, with near real-time mirroring of the original window, great, now I need to make the more complex pipeline work better.

The mixer pipeline below, now updates about once per second (much better than without the "use-damage=false"), but still reports the timestamping error message.

    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 - $y0 )) \
        ! alpha method=green angle=70 \
        ! mixer.sink_1   \
        \
        ximagesrc xid=0x02a00006 use-damage=false ! videoscale \
        ! video/x-raw,width=$w,height=$h ! mixer.sink_0   \
        \
        videomixer name=mixer sink_0::zorder=0 sink_1::zorder=1 \
        ! videoconvert ! autovideosink

Output:

    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.
} * repeats every second or so.

Thanks & regards,
Alain.


> > 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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