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• avcodec/huffyuvenc : sub_left_prediction_bgr32, call dsp after 32 first byte of the...

  2 décembre 2017, par Martin Vignali

  avcodec/huffyuvenc : sub_left_prediction_bgr32, call dsp after 32 first byte of the line in order to try to call the align version (diff bytes have avx2 version)
  

  • [DH] libavcodec/huffyuvenc.c

• Call to avformat_find_stream_info prevents decoding of simple PNG image ?

  10 avril 2014, par kloffy

  I am running into a problem decoding a simple PNG image with libav. The decode_ok flag after the call to avcodec_decode_video2 is set to 0, even though the packet contains the entire image. Through some experimentation, I have managed to pinpoint the issue and it seems related to calling avformat_find_stream_info. If the call is removed, the example runs successfully. However, I would like to use the same code for other media, and calling avformat_find_stream_info is recommended in the documentation.

  The following minimal example illustrates the behavior (unfortunately still a bit lengthy) :

  #include <iostream>
  
  
  
  extern "C"
  
  {
  
  #include <libavformat></libavformat>avformat.h>
  
  #include <libavcodec></libavcodec>avcodec.h>
  
  }
  
  
  
  // Nothing to see here, it&#39;s just a helper function
  
  AVCodecContext* open(AVMediaType mediaType, AVFormatContext* formatContext)
  
  {
  
      auto ret = 0;
  
      if ((ret = av_find_best_stream(formatContext, mediaType, -1, -1, nullptr, 0)) &lt; 0)
  
      {
  
          std::cerr &lt;&lt; "Failed to find video stream." &lt;&lt; std::endl;
  
          return nullptr;
  
      }
  
  
  
      auto codecContext = formatContext->streams[ret]->codec;
  
      auto codec = avcodec_find_decoder(codecContext->codec_id);
  
      if (!codec)
  
      {
  
          std::cerr &lt;&lt; "Failed to find codec." &lt;&lt; std::endl;
  
          return nullptr;
  
      }
  
  
  
      if ((ret = avcodec_open2(codecContext, codec, nullptr)) != 0)
  
      {
  
          std::cerr &lt;&lt; "Failed to open codec context." &lt;&lt; std::endl;
  
          return nullptr;
  
      }
  
  
  
      return codecContext;
  
  }
  
  
  
  // All the interesting bits are here
  
  int main(int argc, char* argv[])
  
  {
  
      auto path = "/path/to/test.png"; // Replace with valid path to PNG
  
      auto ret = 0;
  
  
  
      av_log_set_level(AV_LOG_DEBUG);
  
  
  
      av_register_all();
  
      avcodec_register_all();
  
  
  
      auto formatContext = avformat_alloc_context();
  
      if ((ret = avformat_open_input(&amp;formatContext, path, NULL, NULL)) != 0)
  
      {
  
          std::cerr &lt;&lt; "Failed to open input." &lt;&lt; std::endl;
  
          return -1;
  
      }
  
      av_dump_format(formatContext, 0, path, 0);
  
  
  
  //*/ Info is successfully found, but interferes with decoding
  
      if((ret = avformat_find_stream_info(formatContext, nullptr)) &lt; 0)
  
      {
  
          std::cerr &lt;&lt; "Failed to find stream info." &lt;&lt; std::endl;
  
          return -1;
  
      }
  
      av_dump_format(formatContext, 0, path, 0);
  
  //*/
  
  
  
      auto codecContext = open(AVMEDIA_TYPE_VIDEO, formatContext);
  
  
  
      AVPacket packet;
  
      av_init_packet(&amp;packet);
  
  
  
      if ((ret = av_read_frame(formatContext, &amp;packet)) &lt; 0)
  
      {
  
          std::cerr &lt;&lt; "Failed to read frame." &lt;&lt; std::endl;
  
          return -1;
  
      }
  
  
  
      auto frame = av_frame_alloc();
  
      auto decode_ok = 0;
  
      if ((ret = avcodec_decode_video2(codecContext, frame, &amp;decode_ok, &amp;packet)) &lt; 0 || !decode_ok)
  
      {
  
          std::cerr &lt;&lt; "Failed to decode frame." &lt;&lt; std::endl;
  
          return -1;
  
      }
  
  
  
      av_frame_free(&amp;frame);
  
      av_free_packet(&amp;packet);
  
  
  
      avcodec_close(codecContext);
  
  
  
      avformat_close_input(&amp;formatContext);
  
      av_free(formatContext);
  
  
  
      return 0;
  
  }
  
  </iostream>

  The format dump before avformat_find_stream_info prints :

  Input #0, image2, from '/path/to/test.png' :
    Duration : N/A, bitrate : N/A
      Stream #0:0, 0, 1/25 : Video : png, 25 tbn

  The format dump after avformat_find_stream_info prints :

  Input #0, image2, from '/path/to/test.png' :
    Duration : 00:00:00.04, start : 0.000000, bitrate : N/A
      Stream #0:0, 1, 1/25 : Video : png, rgba, 512x512 [SAR 3780:3780 DAR 1:1], 1/25, 25 tbr, 25 tbn, 25 tbc

  So it looks like the search yields potentially useful information. Can anybody shed some light on this problem ? Other image formats seem to work fine. I assume that this is a simple user error rather than a bug.

  Edit : Debug logging was already enabled, but the PNG decoder does not produce a lot of output. I have also tried setting a custom logging callback.

  Here is what I get without the call to avformat_find_stream_info, when decoding succeeds :

  Statistics : 52125 bytes read, 0 seeks

  And here is what I get with the call to avformat_find_stream_info, when decoding fails :

  Statistics : 52125 bytes read, 0 seeks
  detected 8 logical cores
  

  The image is 52125 bytes, so the whole file is read. I am not sure what the logical cores are referring to.

• avformat/hls : do not call ffurl_seek/ffurl_size on crypto protocol

  10 avril 2014, par Anssi Hannula

  avformat/hls : do not call ffurl_seek/ffurl_size on crypto protocol
  ffurl_seek() will not work even when it should be a no-op, so do not
  
  call it on crypto protocol.
  Also replace use of ffurl_size() for the same reason.
  Reported-by : Michael Schenk <Michael.Schenk@albistechnologies.com>
  
  Signed-off-by : Anssi Hannula <anssi.hannula@iki.fi>
  

  • [DH] libavformat/hls.c