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• avformat_alloc_context returns null

  4 mars 2017, par dk123

  I’m currently trying to play a video from a stream through FFMPEG. I’m currently stuck however on a particular section : regardless of what I do, avformat_alloc_context(); seems to return null.

  Would anyone perhaps know what might be going on ?

  I’ve been referencing the link below :
  Reading a file located in memory with libavformat

• ffmpeg's av_parser_init(AV_CODEC_ID_V210) returns null

  31 mai 2017, par VorpalSword

  I’m trying to read in a .mov file that has video encoded in V210 pixel format (AKA : uncompressed, YCbCr, 10 bits per component) for some image quality tests I’m doing.

  My tech stack is ffmpeg 3.3.1 / gcc / Darwin.

  The decode_video.c example compiles, links & runs just fine but it has the codec ID hard-coded as AV_CODEC_ID_MPEG1VIDEO. I reasonably/naïvely thought that changing this to AV_CODEC_ID_V210 would get me a long way to decoding my test files.

  Unfortunately not. The call to av_parser_init returns null.

  Can anyone tell me why ? And how to fix this ? Thanks.

  #include 
  
  #include 
  
  #include 
  
  
  
  #include <libavcodec></libavcodec>avcodec.h>
  
  
  
  ... // irrelevant code omitted, see linked example for details
  
  
  
  avcodec_register_all();
  
  
  
  pkt = av_packet_alloc();
  
  if (!pkt)
  
      exit(1);
  
  
  
  /* set end of buffer to 0 (this ensures that no overreading happens for damaged MPEG streams) */
  
  memset(inbuf + INBUF_SIZE, 0, AV_INPUT_BUFFER_PADDING_SIZE);
  
  
  
  /* find the MPEG-1 video decoder */
  
  // codec = avcodec_find_decoder(AV_CODEC_ID_MPEG1VIDEO); this works!
  
  codec = avcodec_find_decoder(AV_CODEC_ID_V210);  // this injects my problem
  
  if (!codec) {
  
      fprintf(stderr, "Codec not found\n");
  
      exit(1);
  
  }
  
  
  
  printf ("codec->id: %d, %d\n", AV_CODEC_ID_V210, codec->id); // codec->id: 128, 128
  
  
  
  parser = av_parser_init(codec->id);
  
  if (!parser) {
  
      fprintf(stderr, "parser not found\n");
  
      exit(1);  // program exits here when AV_CODEC_ID_V210 used
  
  }

• ffmpeg compilation problem : avcodec_find_decoder always returns null

  15 mars 2016, par Adion

  I recently tried to upgrade the ffmpeg libraries I use in my Mac OS X application by downloading and compiling ffmpeg from source.

  My code works correctly with pre-compiled libraries of the same version on windows.
  On Mac OS X, the library appears to work (it can open the file and find the streams and codecs used), but when it gets to avcodec_find_decoder, this function always returns null.

  The code has worked with an older version of the library (compiled a year ago on Mac OS X 10.5)

  I configured fmpeg using

  ./configure --extra-cflags="-arch i386" --extra-ldflags='-arch i386' --arch=x86_32 --target-os=darwin --enable-cross-compile --disable-indev=jack --enable-shared --disable-static

  I checked config.mak, and it appears to have the decoders for the file types I tried enabled (ogg, vorbis, avi, mkv, ...)
  I also checked that the correct header files have been used and that the newly compiled library is used.

  I have found only some older posts relating to this issue, but without any solution :

  http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/2007-January/021399.html

  http://libav-users.943685.n4.nabble.com/avcodec-find-decoder-problem-td944800.html

  Edit : checking further, it appears av_codec_next(NULL) returns null as well, which means there isn’t a single codec available, or that first_avcodec in utils.c is not set (I actually haven’t found at all where this variable is set, I would have assumed av_register_all, but I can’t find it there)