[gst-devel] why video do not play frequently under rate control

zhangfei gao gaozhangfei at yahoo.com.cn
Thu May 24 16:11:21 CEST 2007

  I use play VGA size video,  on ARM platform.
  I find video do not play frequently under rate control, and the stream fps is 30/1.
  command line is 
gst-launch filesrc location=*.mpg ! flupsdemux ! mpeg2dec ! overlay2sink
  video play frequently at full speed, do not use timestamp got from demux.
  Instead I use GST_CLOCK_TIME_NONE to send buffer.
Display frames is equal with decode frames.
  mpeg2dec0 totalframes=872
mpeg2dec0 fps=34
mpeg2dec0 cpu usage=81%
  But if I use timestamp from demux, performance downgrade immediately.
display fps is only about 520/872x30 = 18 fps,
video render discard about 872-520=352 frames.
  mpeg2dec0 totalframes=872
mpeg2dec0 fps=30
mpeg2dec0 cpu usage=73%
  My video render overlay2sink is based on GstVideoSink, so timestamp and fps is handle by base class.
  I thought video render discard frame because fps could not reach timestamp.
But for 30 fps stream, why full speed fps can reach 34fps, while using timestamp still can not play frequently.
  Is there any tricky, since the same story on qtdemux and h264dec.
  any idea is welcom!
Thanks in advance

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