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• FFMPEG : Video file to YUV conversion by binary ffmpeg and by code C++ give different results

  30 juin 2016, par Anny G

  Disclaimer : I have looked at the following question,
  FFMPEG : RGB to YUV conversion by binary ffmpeg and by code C++ give different results
  but it didn’t help and it is not applicable to me because I am not using SwsContext or anything.

  Following first few tutorials by http://dranger.com/ffmpeg/, I have created a simple program that reads a video, decodes it and then when the frame is decoded, it writes the raw yuv values to a file (no padding), using the data provided by AVFrame after we successfully decoded a frame. To be more specific, I write out arrays AVFrame->data[0], AVFrame->data[1] and AVFrame->data[2] to a file, i.e. I simply append Y values, then U values, then V values to a file. The file turns out to be of yuv422p format.

  When I convert the same original video to a raw yuv format using the ffmpeg(same version of ffmpeg) command line tool, the two yuv files are the same in size, but differ in content.

  FYI, I am able to play both of the yuv files using the yuv player, and they look identical as well.

  Here is the exact command I run to convert the original video to a yuv video using ffmpeg command line tool

   ~/bin/ffmpeg -i super-short-video.h264 -c:v rawvideo -pix_fmt yuv422p  "super-short-video-yuv422p.yuv"

  What causes this difference in bytes and can it be fixed ? Is there perhaps another way of converting the original video to a yuv using the ffmpeg tool but maybe I need to use different settings ?

  Ffmpeg output when I convert to a yuv format :

  ffmpeg version N-80002-g5afecff Copyright (c) 2000-2016 the FFmpeg developers
  
    built with gcc 4.8 (Ubuntu 4.8.4-2ubuntu1~14.04.1)
  
    configuration: --prefix=/home/me/ffmpeg_build --pkg-config-flags=--static --extra-cflags=-I/home/me/ffmpeg_build/include --extra-ldflags=-L/home/me/ffmpeg_build/lib --bindir=/home/me/bin --enable-gpl --enable-libass --enable-libfdk-aac --enable-libfreetype --enable-libmp3lame --enable-libopus --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265 --enable-nonfree --extra-cflags=-pg --extra-ldflags=-pg --disable-stripping
  
    libavutil      55. 24.100 / 55. 24.100
  
    libavcodec     57. 42.100 / 57. 42.100
  
    libavformat    57. 36.100 / 57. 36.100
  
    libavdevice    57.  0.101 / 57.  0.101
  
    libavfilter     6. 45.100 /  6. 45.100
  
    libswscale      4.  1.100 /  4.  1.100
  
    libswresample   2.  0.101 /  2.  0.101
  
    libpostproc    54.  0.100 / 54.  0.100
  
  Input #0, h264, from 'super-short-video.h264':
  
    Duration: N/A, bitrate: N/A
  
      Stream #0:0: Video: h264 (High), yuv420p, 1280x720, 25 fps, 25 tbr, 1200k tbn
  
  [rawvideo @ 0x24f6fc0] Using AVStream.codec to pass codec parameters to muxers is deprecated, use AVStream.codecpar instead.
  
  Output #0, rawvideo, to 'super-short-video-yuv422p.yuv':
  
    Metadata:
  
      encoder         : Lavf57.36.100
  
      Stream #0:0: Video: rawvideo (Y42B / 0x42323459), yuv422p, 1280x720, q=2-31, 200 kb/s, 25 fps, 25 tbn
  
      Metadata:
  
        encoder         : Lavc57.42.100 rawvideo
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (h264 (native) -> rawvideo (native))
  
  Press [q] to stop, [?] for help
  
  frame=   50 fps=0.0 q=-0.0 Lsize=   90000kB time=00:00:02.00 bitrate=368640.0kbits/s speed=11.3x    
  
  video:90000kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.000000%

• FFMpeg not muxing audio and video

  10 août 2016, par Armen Apresyan

  I’m writing a simple application that is muxing the given mp4 and mp3 files and is extracting mp4 file as result.

  fFmpeg = FFmpeg.getInstance(this);
  
  cmd = new String[] {"-i", videoPath, "-i", audioPath, Environment.getExternalStorageDirectory() + "/output.mp4"};
  
                  fFmpeg.execute(cmd, new ExecuteBinaryResponseHandler() {
  
                      @Override
  
                      public void onStart() {
  
                          super.onStart();
  
                          Log.e(TAG, "Started");
  
                      }
  
  
  
                      @Override
  
                      public void onFailure(String message) {
  
                          super.onFailure(message);
  
                          Log.e(TAG, "failed: " + message);
  
                      }
  
  
  
                      @Override
  
                      public void onProgress(String message) {
  
                          super.onProgress(message);
  
                          Log.e(TAG, "progress: "+ message);
  
                      }
  
  
  
                      @Override
  
                      public void onFinish() {
  
                          super.onFinish();
  
                          Log.e(TAG, "finish");
  
                      }
  
  
  
                      @Override
  
                      public void onSuccess(String message) {
  
                          super.onSuccess(message);
  
                          Log.e(TAG, "success: " + message);
  
                      }
  
                  });

  Where videoPath and audioPath are paths to video and audio, for example storage/emulated/0/source.mp4. But I only get a copy of video file without my audio file attached. What is my mistake ?

• Trying to fix VPlayer's seeking ability, need some guidance [Android FFmpeg]

  1er juin 2016, par vxh.viet

  I’m trying to fix the currently broken seeking ability of VPlayer which is a FFmpeg player for Android. Being a Java developer, C code looks like alien language to me so can only fix it using common logic (which could make any C veteran have a good laugh).

  The relevant file is player.c and I’ll try my best to point out the relevant modification.

  So the basic idea is because FFmpeg’s av_seek_frame is very inaccurate even with AVSEEK_FLAG_ANY so I’m trying to follow this suggestion to seek backward to the nearest keyframe and then decode to the frame I want. One addition note is since I want to seek based on millisecond while the said solution show the way to seek by frame which is potentially a source of problem.

  In the Player I add the following fields :

  struct Player{
  
  ....
  
  AVFrame *frame;
  
  int64_t current_time_stamp;
  
  }; 

  In the player_read_from_stream I modify the seeking part as :

  void * player_read_from_stream(void *data) {
  
      ...
  
      struct DecoderData *decoder_data = data;
  
      int stream_no = decoder_data->stream_no;
  
      AVCodecContext * ctx = player->input_codec_ctxs[stream_no];
  
      ...
  
      // seeking, start my stuff
  
      if(av_seek_frame(player->input_format_ctx, seek_input_stream_number, seek_target, AVSEEK_FLAG_BACKWARD) >= 0){
  
          //seek to key frame success, now need to read every frame from the key frame to our target time stamp
  
  
  
  
  
          while(player->current_time_stamp < seek_target){
  
  
  
              int frame_done;
  
  
  
              while (av_read_frame(player->input_format_ctx, &packet) >= 0) {
  
                  if (packet.stream_index == seek_input_stream_number) {
  
  
  
                      avcodec_decode_video2(ctx, player->frame, &frame_done, &packet);
  
                      LOGI(1,"testing_stuff ctx %d", *ctx);
  
                      if (frame_done) {
  
  
  
                          player->current_time_stamp = packet.dts;
  
                          LOGI(1,"testing_stuff current_time_stamp: %"PRId64, player->current_time_stamp);
  
                          av_free_packet(&packet);
  
                          return;
  
                      }
  
                  }
  
                  av_free_packet(&packet);
  
              }
  
          }
  
  
  
  
  
      }
  
      //end my stuff
  
  
  
      LOGI(3, "player_read_from_stream seeking success");
  
  
  
      int64_t current_time = av_gettime();
  
      player->start_time = current_time - player->seek_position;
  
      player->pause_time = current_time;        
  
  }

  And in player_alloc_frames I allocate the memory for my frame as :

  int player_alloc_frames(struct Player *player) {
  
      int capture_streams_no = player->caputre_streams_no;
  
      int stream_no;
  
      for (stream_no = 0; stream_no < capture_streams_no; ++stream_no) {
  
          player->input_frames[stream_no] = av_frame_alloc();
  
  
  
          //todo: test my stuff
  
          player->frame = av_frame_alloc();
  
          //end test
  
  
  
          if (player->input_frames[stream_no] == NULL) {
  
              return -ERROR_COULD_NOT_ALLOC_FRAME;
  
          }
  
      }
  
      return 0;
  
  }

  Currently it just keep crashing and being a typical Android NDK’s "feature", it just provide a super helpful stack trace :

  libc: Fatal signal 11 (SIGSEGV), code 1, fault addr 0x40 in tid 2717 (FFmpegReadFromS)

  I very much appreciate if anyone could help me solve this problem. Thank you for your time.