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 ! xvimagesink 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 (): /GstPipeline:pipeline0/GstXvImageSink:xvimagesink0: There may be a timestamping problem, or this computer is too slow. What is a timestamping problem and what can I do about it?