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• very low latency streaminig with ffmpeg using a webcam

  22 mars 2017, par userDtrm

  I’m trying to configure ffmpeg to do a real-time video streaming using a webcam. The ffmpeg encoder command I use is as follows.

  ffmpeg -f v4l2 -input_format yuyv422 -s 640x480 -i /dev/video0 -c:v libx264 -profile:v baseline -trellis 0 -subq 1 -level 32 -preset superfast -tune zerolatency -me_method epzs -crf 30 -threads 0 -bufsize 1 -refs 4 -coder 0 -b_strategy 0 -bf 0 -sc_threshold 0 -x264-params vbv-maxrate=2000:slice-max-size=1500:keyint=30:min-keyint=10: -pix_fmt yuv420p -an -f mpegts udp://192.168.1.8:5001

  The ffplay command used to display the video feed is,

  ffplay -analyzeduration 1 -fflags -nobuffer -i udp://192.168.1.8:5001

  However, I’m experiencing a latency of 0.5 - 1.0s latency in the video stream. Is there a way to reduce this to a number less than 100ms. Also, when I replace the v4l2 camera capture with a screen capture using x11grab, the stream is almost real-time and I experience no noticeable delays. Moreover, changing the encoder from x264 to mpeg2 had no effect on the latency. In addition, the statistics from the ffmpeg shows that the encoder is performing at a 30fps rate, which I believe indicates that the encoding is real-time. This leaves me with only one reason for the experienced delay.

  • Is there a significant delay in buffers when using v4l2 during video capturing in a webcam ?
  • I don’t think the transmission delay is in effect in this case as I see no latencies when screen capture is used under the same conditions.
  • Can this latency be further reduced ?. Can someone think of a different encoder configuration to be used instead of the one that I’ve been using ?.

  Any suggestions or assistance is highly appreciated.

  Thank You.

• configure : Check whether MSVC requires using the C89-to-C99 converter

  4 novembre 2013, par Martin Storsjö

  configure : Check whether MSVC requires using the C89-to-C99 converter
  MSVC does support enough of C99 to work without the converter since
  
  the 2013 version. Try to detect which version of the compiler in
  
  the path needs to run the C99 converter or not. When the converter
  
  is omitted, compilation time is reduced quite drastically.
  Prior to this, users could still use —cc="c99conv -noconv cl"
  
  when running MSVC 2013 to achieve the same.
  This checks the version number instead of doing a normal compile
  
  test, since this check needs to be done earlier in configure, before
  
  the normal compile test helpers are usable.
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DH] configure

• Anomalie #3650 : Activation des plugins impossible sous IE10 et IE11

  26 février 2016

  c’est bon pour moi (win 7,IE 11).
  on a le comportement normal. la modale apparait bien et l’activation se fait sans problème.