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• Detect if AVStream is broken

  9 juillet 2018, par Eugene Alexeev

  In my project I’m using an FFMpeg and I wrote a muxer which works with multi-video container (it’s an .mp4 with few video streams). And sometimes I have to deal with a situation when my code was fed up with file which has broken video stream. And the problem is - I need to find a way how I can detect broken stream and abandon it from usage.

  Here’s my code which I’m using for reading streams out of the file :

  - (BOOL)openFile:(NSString *)filePath options:(AVDictionary *)options
  
  {
  
      _pFormatCtx = NULL;
  
  
  
      if (avformat_open_input(&_pFormatCtx, [filePath UTF8String], NULL, &options) != 0) {
  
          [self raiseExceptionWithMessage:@"Couldn't open the file!"];
  
          return NO;
  
      }
  
  
  
      if (avformat_find_stream_info(_pFormatCtx, NULL) < 0) {
  
          //[self raiseExceptionWithMessage:@"Couldn't find stream info!"];
  
          return NO;
  
      }
  
  
  
      int stream_index = 0;
  
      for (int i = 0; i < _pFormatCtx->nb_streams ; i++)
  
      {
  
          AVStream *st = _pFormatCtx->streams[i];
  
          if (_pFormatCtx->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO)
  
          {
  
              AVCodecParameters *params = st->codecpar;
  
              st->index = stream_index;
  
              _streams[@(st->index)] = [[VideoStream alloc] initWithStream:st];
  
              stream_index++;
  
          }
  
      }
  
  
  
      _firstStream = [_streams.allValues firstObject].stream;
  
  
  
      if (_streams.count == 0) {
  
          [self raiseExceptionWithMessage:@"Couldn't find videostream!"];
  
          return NO;
  
      }
  
  
  
      _pCodecParams = [self firstStream]->codecpar;
  
      _pCodec = avcodec_find_decoder(_pCodecParams->codec_id);
  
  
  
      if (!_pCodec) {
  
          [self raiseExceptionWithMessage:@"Unsupported codec!"];
  
          return NO;
  
      }
  
  
  
      _pCodecCtx = avcodec_alloc_context3(_pCodec);
  
      if (avcodec_parameters_to_context(_pCodecCtx, _pCodecParams) < 0) {
  
          [self raiseExceptionWithMessage:@"Couldn't copy params into codec"];
  
          return NO;
  
      }
  
  
  
      if (avcodec_open2(_pCodecCtx, _pCodec, 0) < 0) {
  
          [self raiseExceptionWithMessage:@"Couldn't open the Codec!"];
  
          return NO;
  
      }
  
  
  
      return YES;
  
  }

  When this method is opening video with broken video-stream, avformat_find_stream_info gives such output in logs :

  [h264 @ 0x10684e200] top block unavailable for requested intra mode -1
  
  [h264 @ 0x10684e200] error while decoding MB 45 0, bytestream 76665
  
  [h264 @ 0x10684e200] concealing 3600 DC, 3600 AC, 3600 MV errors in I frame
  
  [h264 @ 0x106854a00] top block unavailable for requested intra mode -1
  
  [h264 @ 0x106854a00] error while decoding MB 47 0, bytestream 69501
  
  [h264 @ 0x106854a00] concealing 3600 DC, 3600 AC, 3600 MV errors in I frame
  
  [h264 @ 0x10683de00] left block unavailable for requested intra4x4 mode -1
  
  [h264 @ 0x10683de00] error while decoding MB 0 1, bytestream 73290
  
  [h264 @ 0x10683de00] concealing 3600 DC, 3600 AC, 3600 MV errors in I frame
  
  [h264 @ 0x106860800] left block unavailable for requested intra4x4 mode -1
  
  [h264 @ 0x106860800] error while decoding MB 0 2, bytestream 23072
  
  [h264 @ 0x106860800] concealing 3559 DC, 3559 AC, 3559 MV errors in I frame

  Good news is avformat_find_stream_info clearly sees that something is wrong with the file. But bad news is - output of avformat_find_stream_info isn’t affected at all. After this method execution my AVFormatContext variable which is _pFormatCtx will have all streams file provides whether it’s valid or not.

  And my question - how can I differ bad stream from a good one ? What kind of data inside the stream I can rely on ? What kind of method I could use to test stream out ? Any help would be appreciated !

• Using ffmpeg with MAMP local server

  22 mai 2012, par dirk_22

  In my MAMP local server home folder on Mac OS X (htdocs), I have a bunch of images (labeled image0 through image(n)) which I would like to stitch together into a jpeg using ffmpeg. When I type the following command into terminal, a .mpg file is successfully generated.

  ffmpeg -f image2 -i image%d.jpg videofile.mpg

  However, when I try to execute the same command using the php code pasted below, nothing seems to happen.

  <?php
  
  shell_exec('ffmpeg -f image2 -i image%d.jpg videofile.mpg');
  
  ?>

  I've copied the installed ffmpeg folder on my home directory into htdocs, but ffmpeg doesn't seem to be accessed. I'm very new to PHP, so please feel free to point out any gross errors in my code. I'd just like the php script to accomplish the same task which terminal executes upon input of the aforementioned command. I'd welcome any and all advice. Cheers.

• Revision 17ea6ab67b : Initialization to prevent asan failure on google3 Reinstates an assignment to p

  13 août 2014, par Deb Mukherjee

  Changed Paths :
   Modify /vpxdec.c

  
  
  Initialization to prevent asan failure on google3

  Reinstates an assignment to prevent an asan failurere on google3.
  Not sure why the failure happens. This was removed in a recent patch
  https://gerrit.chromium.org/gerrit/#/c/71068/.

  Change-Id : Ifd9ccffd4c2164f4de38b21821ffb28bd779b0f3