Still can't get videomixer to do live video at full frame rate

wally bkg wb666greene at
Tue Aug 16 14:03:25 PDT 2011

Trying to display two genlocked camera images from two v4l2 capture devices
in a single frame, ultimately to an appsink.

This pipeline works but can't get full frame rate :(

gst-launch v4l2src device=/dev/video0 ! queue ! \
video/x-raw-yuv,format =\(fourcc\)I420, framerate=\(fraction\)30000/1001,
width=640, height=480 ! \
videomixer name=mix sink_0::alpha=1.0 sink_0::xpos=0 sink_0::ypos=0
sink_1::alpha=1.0 sink_1::xpos=0 sink_1::ypos=480  \
sink_2::zorder=3  !   xvimagesink \
v4l2src device=/dev/video1 ! queue ! video/x-raw-yuv,format=\(fourcc\)I420,
framerate=\(fraction\)30000/1001, width=640, height=480 ! mix. \
videotestsrc pattern=2 ! queue ! video/x-raw-yuv,format=\(fourcc\)I420,
framerate=\(fraction\)1/1, width=640, height=960 ! mix.

Top shows the gst-launch command running 7-12% CPU.

I can add a second xvimagesink while the above is running with:

gst-launch v4l2src device=/dev/video4 !  video/x-raw-yuv,format
=\(fourcc\)I420, framerate=\(fraction\)30000/1001, width=640, height=480 !

and it displays at full frame rate even though it shows 34-45% CPU in top
while running.  Xorg always stays below 10%.

Occasionally the videomixer gst-launch command spits out (not often, but I
saw it this time and its why I'm posting this) a warning message:

WARNING: from element /GstPipeline:pipeline0/GstXvImageSink:xvimagesink0: A
lot of buffers are being dropped.
Additional debug info:
gstbasesink.c(2597): gst_base_sink_is_too_late ():
There may be a timestamping problem, or this computer is too slow.

What is a timestamping problem and what can I do about it?
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