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• Use M4S2 as default video tag for MPEG-4 ASP in asf.

  5 octobre 2011, par Carl Eugen Hoyos

  Use M4S2 as default video tag for MPEG-4 ASP in asf.

• Getting artifacts when trying to read video stream from YouTube

  23 février 2012, par givi

  I'm trying to read the video frames from the RTSP stream that I get from YouTube. Here is the link for my test video :

  rtsp ://v8.cache5.c.youtube.com/CiILENy73wIaGQkJlrXMiAG8BxMYDSANFEgGUgZ2aWRlb3MM/0/0/0/video.3gp

  If I'm reading frames from the local file - everything is fine, but when read them from a stream I get nothing but lots of artifacts. I've googled around and found out that there might be a problem with UDP packets and switching to TCP may help but I really can't find where it is possible to change this.

  Here is the function for reading a frame :

  bool nextFrame(AVFormatContext *pFormatCtx, AVCodecContext *pCodecCtx, int videoStream, AVFrame *pFrame) {  AVPacket packet;
  
      int frameFinished = 0;
  
  
  
      while( !frameFinished && av_read_frame(pFormatCtx, &packet) >= 0 ) {
  
          // Is this a packet from the video stream?
  
          if( packet.stream_index == videoStream ) {
  
              // Decode video frame
  
              avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished, &packet);
  
          }
  
  
  
          // Free the packet that was allocated by av_read_frame
  
          av_free_packet(&packet);    
  
         }    
  
         return frameFinished!=0;  
  
  }

  I'm also getting lots of error messages in my log :

  [h263 @ 0x7804c00] warning: first frame is no keyframe
  
  [h263 @ 0x7804c00] illegal ac vlc code at 6x1
  
  [h263 @ 0x7804c00] Error at MB: 18
  
  [h263 @ 0x7804c00] concealing 99 DC, 99 AC, 99 MV errors
  
  [h263 @ 0x7804c00] I cbpy damaged at 10 4
  
  [h263 @ 0x7804c00] Error at MB: 58
  
  [h263 @ 0x7804c00] concealing 99 DC, 99 AC, 99 MV errors
  
  [h263 @ 0x7804c00] I cbpy damaged at 6 6
  
  [h263 @ 0x7804c00] Error at MB: 78
  
  [h263 @ 0x7804c00] concealing 76 DC, 76 AC, 76 MV errors
  
  [h263 @ 0x7804c00] I cbpy damaged at 5 5
  
  [h263 @ 0x7804c00] Error at MB: 65
  
  [h263 @ 0x7804c00] concealing 88 DC, 88 AC, 88 MV errors
  
  [h263 @ 0x7804c00] illegal ac vlc code at 7x5
  
  [h263 @ 0x7804c00] Error at MB: 67
  
  [h263 @ 0x7804c00] concealing 86 DC, 86 AC, 86 MV errors

  ...and so on

  edit : this is 99.9% a UDP-TCP problem. I've found this link :

  rtsp ://195.200.199.8/mpeg4/media.amp

  This is some test camera available online. It streams with artifacts. However if it has get parameter 'tcp' and if I use this

  rtsp ://195.200.199.8/mpeg4/media.amp ?tcp

  everything works without artifacts.

  So to correct my question : is there any way to force YouTube or ffmpeg to use TCP ?

• Alternative to ffmpeg for dynamically creating video thumbnails

  3 novembre 2013, par user763852

  The server hosting my website doesn't have ffmpeg and I am not allowed to install any additional extensions. Is there any other way I can make video thumbnails dynamically ? Perhaps some kind of web service, where I pass the video file and as a result I get a picture file. I'm using php, by the way.