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• reading videos in matlab not working (the following codec(s) to be installed on your system)

  20 février 2016, par Ehab AlBadawy

  When I try to read a video in matlab v = VideoReader('t.avi'); I get this error :

  The file requires the following codec(s) to be installed on your system:
  
      video/x-msvideo

  and some time it needs mpeg codec when I try to load mpeg or mp4 video.

  I found someone referring to rename libstdc++.so.6.0 to libstdc++.so.6.0.10 but I found that I already have libstdc++.so.6.0.13

  I’m using matlab 2013 with archlinux.

  Update : I get this warring in the terminal when trying to read a video

  Failed to load plugin '/usr/lib/gstreamer-0.10/libgstpango.so':
  
  /usr/lib/libharfbuzz.so.0: undefined symbol: FT_Face_GetCharVariantIndex

• lavf/mp3 : Properly check return values of seeks and reads while reading the header

  26 février 2016, par Derek Buitenhuis

  lavf/mp3 : Properly check return values of seeks and reads while reading the header
  Fixes large amounts of seeking past EOF, which could be extremely
  
  slow over a network.
  Signed-off-by : Derek Buitenhuis <derek.buitenhuis@gmail.com>
  

  • [DH] libavformat/mp3dec.c

• Can't detect bad/corrupted video frames when reading video file with ffmpeg libraries

  8 mars 2016, par Nextor

  I recently started to use ffmpeg C libraries in order to analyze the integrity of video frames in a file. I started (like a lot of people) with Dranger’s tutorials, then I made my own research from them. But I have a problem : I can’t detect corrupted packets or frames while reading a video file with corrupted data. For example, there is this code below (it does work but I haven’t worried too much about freeing resources) :

  extern "C" {
  
  #include 
  
  #include 
  
  #include 
  
  }
  
  #pragma comment(lib, "avformat.lib")
  
  #pragma comment(lib, "avcodec.lib")
  
  #pragma comment(lib, "avutil.lib")
  
  
  
  int main(int argc, char *argv[]) {
  
  
  
  av_register_all();
  
  
  
  AVFormatContext* pFormatContext = 0;
  
  
  
  if (avformat_open_input(&pFormatContext, "errorVideo.mpg", NULL, NULL) < 0) {
  
      //Error opening file
  
      exit(1);
  
      }
  
  
  
  if (avformat_find_stream_info(pFormatContext, NULL) < 0) {
  
      //Error finding stream...
  
      exit(1);
  
      }
  
  
  
  //Finding first video stream:
  
  unsigned int iStream;
  
  for (iStream = 0; iStream < pFormatContext->nb_streams && pFormatContext->streams[iStream]->codec->codec_type != AVMEDIA_TYPE_VIDEO;    iStream++);
  
  if (iStream >= pFormatContext->nb_streams) {
  
      //Error finding video stream.
  
      exit(1);
  
      }
  
  
  
  AVCodecContext* pOrigCodecCtx = pFormatContext->streams[iStream]->codec;
  
  AVCodec* pCodec = avcodec_find_decoder(pOrigCodecCtx->codec_id);
  
  if (!pCodec) {
  
      //Codec no supported
  
      exit(1);
  
      }
  
  
  
  AVCodecContext* pNewCodecCtx = avcodec_alloc_context3(pCodec);
  
  if (!pNewCodecCtx || avcodec_copy_context(pNewCodecCtx, pOrigCodecCtx) != 0) {
  
      //Error allocating or copying context
  
      exit(1);
  
      }
  
  
  
  if (avcodec_open2(pNewCodecCtx, pCodec, NULL) < 0) {
  
      //Error initializing codec
  
      exit(1);
  
      }
  
  
  
  AVPacket packet;
  
  int gotFrame;
  
  while (av_read_frame(pFormatContext, &packet) >= 0) {
  
  
  
      if (packet.stream_index == iStream) {
  
          AVFrame* pFrame = av_frame_alloc();
  
  
  
          if (avcodec_decode_video2(pNewCodecCtx, pFrame, &gotFrame, &packet) < 0) {
  
              //Error decoding frame.
  
              exit(1);
  
              }
  
  
  
          if (gotFrame) {
  
              //do something with frame...
  
              }
  
  
  
          av_frame_unref(pFrame);
  
          }
  
  
  
      av_free_packet(&packet);
  
      }
  
  if (pFormatContext->pb->error != 0) {
  
      //Error reading packet
  
      exit(1);
  
      }
  
  }

  When I try to read a video with corrupted data, I get output from the ffmpeg libraries indicating that there is invalid data, e.g. :

  [mpeg2video @ 0000000000B68A40] invalid cbp -1 at 19 6
  
  [mpeg2video @ 0000000000B68A40] Warning MVs not available
  
  [mpeg2video @ 0000000000B68A40] concealing 45 DC, 45 AC, 45 MV errors in P frame
  
  [mpeg2video @ 0000000000B68A40] invalid mb type in P Frame at 21 16
  
  [mpeg2video @ 0000000000B68A40] Warning MVs not available
  
  [mpeg2video @ 0000000000B68A40] concealing 45 DC, 45 AC, 45 MV errors in P frame
  
  [mpeg2video @ 0000000000B68A40] slice mismatch
  
  [mpeg2video @ 0000000000B68A40] 00 motion_type at 25 8
  
  [mpeg2video @ 0000000000B68A40] Warning MVs not available
  
  [mpeg2video @ 0000000000B68A40] concealing 90 DC, 90 AC, 90 MV errors in B frame

  but I can’t detect all those failing frames from my code : neither av_read_frame nor avcodec_decode_video2 functions ever return error codes ! What am I doing wrong ?