[Libav-user] Incorrect Display Aspect Ratio

[Lyndon Hill]

Hi,

I'm having trouble finding the correct aspect for displaying anamorphic video from an MTS.

If I use ffprobe I get the result (truncated):
Stream #0:0[0x515]: Video: mpeg2video (Main) ([2][0][0][0] / 0x0002), yuv420p(tv), 720x576 [SAR 64:45 DAR 16:9], max. 2972 kb/s, 25 fps, 25 tbr, 90k tbn, 50 tbc

So the DAR is 16:9. Using my code, I get a SAR of 0:1 which the docs say means unknown.

My code:

// testdar.cc
// clang++ testdar.cc -o testdar (pkg-config --cflags ffmpeg) (pkg-config --libs ffmpeg)

extern "C"
{
  #include <libavcodec/avcodec.h>
  #include <libavformat/avformat.h>
}

#include <iostream>

int main(int argc, char *argv[])
{
  avcodec_register_all();
  av_register_all();

   AVFormatContext *format;
   if(avformat_open_input(&format,
                                                 "2015071421565301.mts",
                                                 NULL, NULL) < 0)
       return(1);


  if(avformat_find_stream_info(format, NULL) < 0)
  {
       avformat_close_input(&format);
       return(1);
  }

  AVCodec *video_codec;
   int stream = av_find_best_stream(format,
                                                                     AVMEDIA_TYPE_VIDEO,
                                                                     -1, -1,
                                                                     &video_codec,
                                                                     0);
   if(stream < 0)
   {
       avformat_close_input(&format);
       return(1);
   }

   AVCodecContext *codec_ctx;
   codec_ctx = format->streams[stream]->codec;
   if(avcodec_open2(codec_ctx, video_codec, NULL) < 0)
   {
       avformat_close_input(&format);
       return(1);
   }

   std::cout << "Aspect ratio = "
                       << format->streams[stream]->sample_aspect_ratio.num 
                       << ":" << format->streams[stream]->sample_aspect_ratio.den << "\n";

   return(0);
}

Result (truncated):
$ ./testdar
Aspect ratio = 0:1


thanks in advance

L. Hill