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• I need a compact c/c++ code for motion vectors extraction from mp4 file without frame decoding [on hold]

  23 mars 2018, par Andyrey

  I have searched a lot of answers on this kind of question. Many of them point out to code, presuming frame decoding :

  DCT coefficient and motion vector extraction in encoded domain ;
  https://github.com/vadimkantorov/mpegflow ;
  https://github.com/FFmpeg/FFmpeg/blob/master/doc/examples/extract_mvs.c.

  I implemented these codes in my program and saw they decode video frames, and then use frame side data for extracting motion vectors.

  Others give command lines for executing bynaries :

  Motion Vector extraction from encoded video file

  or just gives reference to huge set of library files with no idea what to do with them.

  What I badly need : code for extracting motion vectors from mp4 with no frame decoding (no pixel domain restoring). Is it possible ?

  From my 3rd reference I used code like next, where I suspect frame decoding happens :

  while (ret >= 0)
  
  {
  
      ret = avcodec_receive_frame(video_dec_ctx, frame);
  
     /*I omit some exclusion processing*/
  
      if (ret >= 0)
  
      {
  
          int i;
  
          AVFrameSideData *sd;
  
          video_frame_count++;
  
          sd = av_frame_get_side_data(frame, AV_FRAME_DATA_MOTION_VECTORS);
  
          if (sd)
  
          {
  
              const AVMotionVector *mvs = (const AVMotionVector *)sd->data;
  
              for (i = 0; i < sd->size / sizeof(*mvs); i++)
  
              {
  
                  const AVMotionVector *mv = &mvs[i];
  
                  printf("%d,%2d,%2d,%2d,%4d,%4d,%4d,%4d,0x%"PRIx64"\n",
  
                  video_frame_count, mv->source,
  
                  mv->w, mv->h, mv->src_x, mv->src_y,
  
                  mv->dst_x, mv->dst_y, mv->flags);
  
              }
  
          } 
  
          av_frame_unref(frame);
  
      }
  
  }

• Working with ffmpeg in Xamarin Android

  8 janvier 2018, par Ahmed Mujtaba

  I’m building an android app using Xamarin. The requirement of the app is to capture video from the camera and encode the video to send it across to a server. Initially I was using an encoder library on the server side to encode recorded video but it was proving to be extremely unreliable and inefficient specially for large sized video files. I have posted my issues on another thread here I then decided to encode the video on the client side and then send it to the server. I’ve found encoding to be a bit complicated and there isn’t much information available on how this can be done so I search for the only way I knew how to encode a video that is by using ffmpeg codec. I’ve found some solutions. There’s a project on github that demonstrates how ffmpeg is used inside a Xamarin android project. However running the solution doesn’t give any output. The project has a binary ffmpeg file which is installed to the phone directory using the code below :

  _ffmpegBin = InstallBinary(XamarinAndroidFFmpeg.Resource.Raw.ffmpeg, "ffmpeg", false);

  Below is the example code for encoding video into different set of outputs :

              _workingDirectory = Android.OS.Environment.ExternalStorageDirectory.AbsolutePath;
  
          var sourceMp4 = "cat1.mp4";
  
          var destinationPathAndFilename = System.IO.Path.Combine (_workingDirectory, "cat1_out.mp4");
  
          var destinationPathAndFilename2 = System.IO.Path.Combine (_workingDirectory, "cat1_out2.mp4");
  
          var destinationPathAndFilename4 = System.IO.Path.Combine (_workingDirectory, "cat1_out4.wav");
  
          if (File.Exists (destinationPathAndFilename))
  
              File.Delete (destinationPathAndFilename);
  
          CreateSampleFile(Resource.Raw.cat1, _workingDirectory, sourceMp4);
  
  
  
  
  
          var ffmpeg = new FFMpeg (this, _workingDirectory);
  
  
  
          var sourceClip = new Clip (System.IO.Path.Combine(_workingDirectory, sourceMp4));
  
  
  
          var result = ffmpeg.GetInfo (sourceClip);
  
  
  
          var br = System.Environment.NewLine;
  
  
  
          // There are callbacks based on Standard Output and Standard Error when ffmpeg binary is running as a process:
  
  
  
          var onComplete = new MyCommand ((_) => {
  
              RunOnUiThread(() =>_logView.Append("DONE!" + br + br));
  
          });
  
  
  
          var onMessage = new MyCommand ((message) => {
  
              RunOnUiThread(() =>_logView.Append(message + br + br));
  
          });
  
  
  
          var callbacks = new FFMpegCallbacks (onComplete, onMessage);
  
  
  
          // 1. The idea of this first test is to show that video editing is possible via FFmpeg:
  
          // It results in a 150x150 movie that eventually zooms on a cat ear. This is desaturated, and there's a fade in.
  
  
  
          var filters = new List<videofilter> ();
  
          filters.Add (new FadeVideoFilter ("in", 0, 100));
  
          filters.Add(new CropVideoFilter("150","150","0","0"));
  
          filters.Add(new ColorVideoFilter(1.0m, 1.0m, 0.0m, 0.5m, 1.0m, 1.0m, 1.0m, 1.0m));
  
          var outputClip = new Clip (destinationPathAndFilename) { videoFilter = VideoFilter.Build (filters)  };
  
          outputClip.H264_CRF = "18"; // It's the quality coefficient for H264 - Default is 28. I think 18 is pretty good.
  
          ffmpeg.ProcessVideo(sourceClip, outputClip, true, new FFMpegCallbacks(onComplete, onMessage));
  
  
  
          //2. This is a similar version version in command line only:
  
          string[] cmds = new string[] {
  
              "-y",
  
              "-i",
  
              sourceClip.path,
  
              "-strict",
  
              "-2",
  
              "-vf",
  
              "mp=eq2=1:1.68:0.3:1.25:1:0.96:1",
  
              destinationPathAndFilename2,
  
              "-acodec",
  
              "copy",
  
          };
  
          ffmpeg.Execute (cmds, callbacks);
  
  
  
          // 3. This lists codecs:
  
          string[] cmds3 = new string[] {
  
              "-codecs",
  
          };
  
          ffmpeg.Execute (cmds, callbacks);
  
  
  
          // 4. This convers to WAV
  
          // Note that the cat movie just has some silent house noise.
  
          ffmpeg.ConvertToWaveAudio(sourceClip, destinationPathAndFilename4, 44100, 2, callbacks, true);
  
  </videofilter>

  I have tried different commands but no output file is generated. I have tried to use another project found here but this one has the same issue. I don’t get any errors but no output file is generated. I’m really hoping someone can help me find a way I can manage to use ffmpeg in my project or some way to compress video to transport it to the server.

  I will really appreciate if someone can point me to the right direction.

• avcodec/cfhd : Move peak_table() and difference_coding() calls after the existing...

  13 août 2018, par Michael Niedermayer

  avcodec/cfhd : Move peak_table() and difference_coding() calls after the existing coefficient count check
  Fixes : out of array access
  
  Fixes : 9509/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_CFHD_fuzzer-5283250636324864
  
  Fixes : 9572/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_CFHD_fuzzer-4920757409808384
  
  Fixes : 9596/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_CFHD_fuzzer-5114917580439552
  
  Fixes : 9640/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_CFHD_fuzzer-6247840698335232
  
  Fixes : 9659/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_CFHD_fuzzer-6079554987753472
  Found-by : continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavcodec/cfhd.c