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• Error in ffmpeg when reading from UDP stream

  24 juillet 2013, par six6and1one

  I'm trying to process frames from a UDP stream using ffmpeg. Everything will run fine for a while but av_read_frame() will always eventually return either AVERROR_EXIT (Immeditate exit requested) or -5 (Error number -5 occurred) while the stream should still be running fine. Right before the error it always prints the following message to the console

  [mpeg2video @ 0caf6600] ac-tex damaged at 14 10
  
  [mpeg2video @ 0caf6600] Warning MVs not available
  
  [mpeg2video @ 0caf6600] concealing 800 DC, 800 AC, 800 MV errors in I frame

  (the numbers in the message vary from run to run)

  I have a suspicion that the error is related to calling av_read_frame too quickly. If I have it run as fast as possible, I usually get an error within 10-20 frames, but if I put a sleep before reading it will run fine for a minute or so and then exit with an error. I realize this is hacky and assume there is a better solution. Bottom line : is there a way to dynamically check if 'av_read_frame()' is ready to be called ? or a way to supress the error ?

  Psuedo code of what I'm doing below. Thanks in advance for the help !

  void getFrame()
  
  {
  
      //wait here?? seems hacky...
  
      //boost::this_thread::sleep(boost::posix_time::milliseconds(25));   
  
  
  
      int av_read_frame_error = av_read_frame(m_input_format_context, &m_input_packet);           
  
      if(av_read_frame_error == 0){       
  
          //DO STUFF - this all works fine when it gets here
  
      }
  
      else{               
  
          //error
  
          char errorBuf[AV_ERROR_MAX_STRING_SIZE];
  
          av_make_error_string(errorBuf, AV_ERROR_MAX_STRING_SIZE, av_read_frame_error);
  
          cout << "FFMPEG Input Stream Exit Code: " << av_read_frame_error << "   Message: " << errorBuf << endl;             
  
      }
  
  }

• How to reencode a h264 wiiU to a standard format video

  26 juin 2016, par didix16

  I’m trying to make a bridge between wiiU and web interface to view the video h264 signal. I’m not familiar with video programming but I’m searching some info about it. Following this documentation :

  • http://libdrc.org/docs/re/sc-vstrm.html
  • http://libdrc.org/docs/installation.html#patched-dependencies

  It says that wiiU works with a H.264 variation. So since there is someone who made a h264decoder of wiiU in python (https: //github.com/justjake/drc-sim-keyboard/blob/master/H264Decoder.py) I’ll want to decode that kind of h264 and transform it to some kind of standard video for stream and get it over <video></video> tag on a html5 web page. It is possibly do it with ffmpeg libraries ?

  If it, can someone tell me how ? I’m programming the bridge in C++.

  Oh yes, at the moment I’m capturing the data from udp socket, so I just need transform the incoming data detailed in sc-vstrm.html documentation into some web stream video standard.

  Thank you so much guys :).

• "Widen" the stereo with Web Audio API

  20 février 2018, par Dan P.

  I am trying to use the Web Audio API to match an ffmpeg command I run on the server to widen the stereo of a audio tracks.

  With ffmpeg, I use : https://ffmpeg.org/ffmpeg-filters.html#stereowiden

  More specifically, this my ffmpeg command : stereowiden=delay=1:feedback=0.13:crossfeed=0:drymix=1

  In JS with the Web Audio API I’ve tried using the StereoPanNode (https://developer.mozilla.org/en-US/docs/Web/API/StereoPannerNode) but this only seems to pan the audio left and right. I’ve also tried to combine it with the DelayNode (https://developer.mozilla.org/en-US/docs/Web/API/DelayNode), still in vain.

  How would you achieve that ?