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• FFMPEG read audio convenience function

  7 mars 2016, par Phlox Midas

  In Matlab, there’s a function called audioread that takes a file name as input and returns a vector of samples and the sample rate like this :

  [samples, sampleRate] = audioread(fileName);

  I’ve been programming FFMPEG but finding it very low level. I have a file being read using a technique similiar to this. Is there any such equivalent C function in FFMPEG as there is in Matlab so I don’t have to fiddle with the low level stuff ? Or any library that can provide a nice API like this for FFMPEG (though I would just prefer this one function) ?

• lavu : add av_gettime_relative()

  12 mai 2014, par Olivier Langlois

  lavu : add av_gettime_relative()
  These functions are using the POSIX clock_gettime() function with the
  
  CLOCK_MONOTONIC clock id. If these are not present on the targeted
  
  platform, the new functions will fallback on using the original realtime functions
  
  av_gettime() and av_usleep().
  Monotonic support can be added on other platforms with their
  
  equivalent native system API eventually if possible.
  Whenever time is requested to measure relative time, the monotonic clock,
  
  when available, is superior to the system realtime clock because it is
  
  not affected by discontinuous jumps in the system time
  In a future step, offering the flexibility to let the user choose between
  
  rt and monotonic clock for avdevices packets will be investigated.
  It is very easy to experience the issues that this patch attempt to address
  
  by rewinding back in the past the system time while ffmpeg is running.
  this is breaking the ffmpeg report printing (ffmepg.c:print_report()) and
  
  the the rate emulator functionality (-re) without the patch.
  Signed-off-by : Olivier Langlois <olivier@trillion01.com>
  
  Signed-off-by : Michael Niedermayer <michaelni@gmx.at>
  

  • [DH] doc/APIchanges
  • [DH] libavutil/time.c
  • [DH] libavutil/time.h
  • [DH] libavutil/version.h

• Splitting odd and even frames in Gstreamer

  4 avril 2014, par user3498379

  I am building an application whereby I need to split a videostream(RTSP/MJPEG) into individual frames. The extracted frames then need to be put into two named pipes. I need to alternate the frames between two named pipes, i.e. even frames go to pipe one and odd frames go to pipe 2. I have been able to achieve this with ffmpeg using the following command :

  ffmpeg -i "rtsp://<ipaddress>/axis-media/media.amp?videocodec=jpeg" -vf select="mod(n-1\,2)" -vcodec mjpeg -f avi -y  -vf select="not(mod(n-1\,2))" -vcodec mjpeg -f avi -y 
  
  </ipaddress>

  However I have run into an RTP packet size issue with ffmpeg when using large resolutions e.g. 2048x1536. My question is ; is there a gstreamer equivalent command ? I have the basic gstreamer command which extracts images :

   gst-launch rtspsrc location=rtsp://<ipaddress>/axis-media/media.amp?videocodec=jpeg ! decodebin2 ! jpegenc ! multifilesink location="frame%d.jpg"
  
  </ipaddress>

  But now I need the additional piece, any help will be much appreciated.