[FFmpeg-trac] #1169(avcodec:new): Last 11 Frames Are Skipped

[FFmpeg]

#1169: Last 11 Frames Are Skipped
--------------------------------------+---------------------------------
               Reporter:  mbradshaw   |                  Owner:
                   Type:  defect      |                 Status:  new
               Priority:  normal      |              Component:  avcodec
                Version:  git-master  |               Keywords:
             Blocked By:              |               Blocking:
Reproduced by developer:  0           |  Analyzed by developer:  0
--------------------------------------+---------------------------------
 While working on a video reader I found I wasn't seeing all the frames
 from the video. It's possible I'm doing something wrong, but I haven't
 found any documentation that says I need to do anything special for
 decoding H264 video. The `av_read_frame(formatContext, &packet)` returns
 nonzero 11 frames before the end of the video.

 I transcoded the video with ffmpeg to mpeg2video, and the transcoded video
 did not show the same problem.

 '''Minimal Reproducible Code Sample'''
 {{{
 #include <fstream>

 extern "C"
 {
 #include <avcodec.h>
 #include <avformat.h>
 #include <swscale.h>
 };

 void saveFrame(const AVFrame* frame, int width, int height, int
 frameNumber)
 {
     char filename[32];
     sprintf(filename, "frame%d.ppm", frameNumber);
     std::ofstream file(filename, std::ios_base::binary |
                                  std::ios_base::trunc |
                                  std::ios_base::out);

     if (!file.good())
     {
         throw std::runtime_error("Unable to open the file to write the
 frame");
     }

     file << "P5\n" << width << '\n' << height << "\n255\n";

     for (int i = 0; i < height; ++i)
     {
         file.write((char*)(frame->data[0] + i * frame->linesize[0]),
 width);
     }
 }

 int main()
 {
     av_register_all();
     AVFrame* frame = avcodec_alloc_frame();
     if (!frame)
     {
         return 1;
     }

     AVFormatContext* formatContext = NULL;
     if (avformat_open_input(&formatContext, "in.mov", NULL, NULL) != 0)
     {
         av_free(frame);
         return 1;
     }

     if (avformat_find_stream_info(formatContext, NULL) < 0)
     {
         av_free(frame);
         av_close_input_file(formatContext);
         return 1;
     }

     if (formatContext->nb_streams < 1 ||
         formatContext->streams[0]->codec->codec_type !=
 AVMEDIA_TYPE_VIDEO)
     {
         av_free(frame);
         av_close_input_file(formatContext);
         return 1;
     }

     AVStream* stream = formatContext->streams[0];
     AVCodecContext* codecContext = stream->codec;

     codecContext->codec = avcodec_find_decoder(codecContext->codec_id);
     if (codecContext->codec == NULL)
     {
         av_free(frame);
         avcodec_close(codecContext);
         av_close_input_file(formatContext);
         return 1;
     }
     else if (avcodec_open2(codecContext, codecContext->codec, NULL) != 0)
     {
         av_free(frame);
         avcodec_close(codecContext);
         av_close_input_file(formatContext);
         return 1;
     }

     AVPacket packet;
     av_init_packet(&packet);

     std::ofstream stats("stats.txt");

     int frameNumber = 0;
     while (av_read_frame(formatContext, &packet) == 0)
     {
         if (packet.stream_index == stream->index)
         {
             int frameFinished = 0;
             avcodec_decode_video2(codecContext, frame, &frameFinished,
 &packet);

             if (frameFinished)
             {
                 saveFrame(frame, codecContext->width,
 codecContext->height, frameNumber++);
                 stats << "repeat: " << frame->repeat_pict
                       << "\tkeyframe: " << frame->key_frame
                       << "\tbest_ts: " << frame->best_effort_timestamp <<
 '\n';
             }
         }
     }

     av_free_packet(&packet);
     av_free(frame);
     avcodec_close(codecContext);
     av_close_input_file(formatContext);
 }
 }}}

 '''Config options:''' ./configure --arch=x86 --enable-shared --disable-
 static
 '''FFmpeg/libavcodec compiler:''' GCC/MinGW
 '''Compiler for above sample:''' VC++ 2010
 '''Expected output:''' frame0.ppm to frame 360.ppm
 '''Actual output:''' frame0.ppm to frame 349.ppm

 '''ffmpeg.exe -i in.mov'''
 {{{
 ffmpeg version 0.10.2.git-a45605a Copyright (c) 2000-2012 the FFmpeg
 developers
   built on Apr  4 2012 12:58:46 with gcc 4.6.1
   configuration: --arch=x86 --enable-shared --disable-static
   libavutil      51. 44.100 / 51. 44.100
   libavcodec     54. 12.100 / 54. 12.100
   libavformat    54.  3.100 / 54.  3.100
   libavdevice    53.  4.100 / 53.  4.100
   libavfilter     2. 66.101 /  2. 66.101
   libswscale      2.  1.100 /  2.  1.100
   libswresample   0. 10.100 /  0. 10.100
 Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'in.mov':
   Metadata:
     major_brand     : qt
     minor_version   : 512
     compatible_brands: qt
     encoder         : Lavf54.3.100
   Duration: 00:00:15.13, start: 0.000000, bitrate: 1002 kb/s
     Stream #0:0(eng): Video: h264 (Baseline) (avc1 / 0x31637661), yuv420p,
 852x480 [SAR 1:1 DAR 71:40], 1000 kb/s, 23.92 fps, 24 tbr, 600 tbn, 47.95
 tbc
     Metadata:
       handler_name    : ♂DataHandler
 }}}

 Sample video attached.

-- 
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/1169>
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