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• What is the most performant way to render unmanaged video frames in WPF ?

  18 avril 2017, par superware

  I’m using FFmpeg library to receive and decode H.264/MPEG-TS over UDP with minimal latency (something MediaElement can’t handle).

  On a dedicated FFmpeg thread, I’m pulling PixelFormats.Bgr32 video frames for display. I’ve already tried InteropBitmap :

  _section = CreateFileMapping(INVALID_HANDLE_VALUE, IntPtr.Zero, PAGE_READWRITE, 0, size, null);
  
  _buffer = MapViewOfFile(_section, FILE_MAP_ALL_ACCESS, 0, 0, size);
  
  Dispatcher.Invoke((Action)delegate()
  
  {
  
      _interopBitmap = (InteropBitmap)Imaging.CreateBitmapSourceFromMemorySection(_section, width, height, PixelFormats.Bgr32, (int)size / height, 0);
  
      this.Source = _interopBitmap;
  
  });

  And then per frame update :

  Dispatcher.Invoke((Action)delegate()
  
  {
  
      _interopBitmap.Invalidate();
  
  });

  But performance is quite bad (skipping frames, high CPU usage etc).

  I’ve also tried WriteableBitmap : FFmpeg is placing frames in _writeableBitmap.BackBuffer and per frame update :

  Dispatcher.Invoke((Action)delegate()
  
  {
  
      _writeableBitmap.Lock();
  
  });
  
  try
  
  {
  
      ret = FFmpegInvoke.sws_scale(...);
  
  }
  
  finally
  
  {
  
      Dispatcher.Invoke((Action)delegate()
  
      {
  
          _writeableBitmap.AddDirtyRect(_rect);
  
          _writeableBitmap.Unlock();
  
      });
  
  }

  Experiencing almost the same performance issues (tested with various DispatcherPriority).

  Any help will be greatly appreciated.

• avfilter/vf_geq : use per-thread AVExpr for expression evaluation

  28 décembre 2019, par Marton Balint

  avfilter/vf_geq : use per-thread AVExpr for expression evaluation
  There was no consensus about separating AVExprState from AVExpr so here is a
  
  minimal patch using the existing AVExpr to fix ticket #7528.
  Signed-off-by : Marton Balint <cus@passwd.hu>
  

  • [DH] doc/filters.texi
  • [DH] libavfilter/vf_geq.c

• ffmpeg trimming audio WAV files and setting timecode

  14 juillet 2022, par user19551045

  I am currently trying to cut an audio file to match the length of a video (without combining the two...just looking at timecodes) and produce a trimmed audio file that has a timecode that will match up with the video, the video is considered the absolute truth.

  


  Currently, the issue is that the timecodes from the original audio file do not get carried over into the new cropped audio file. So, the starting timecode is now 00:00:00:00 instead of say 07:20:02:14. Even using the -timecode commands and trying to hardcode the timecode that way doesn't seem to do the trick. I am wondering if there is any way around this ? I just want to do as minimal to the raw audio as possible...just change the audio file's length while setting the timecodes so the new audio will line up with the video. Any thoughts/suggestions welcome !

  


  Currently I have tried two options that don't seem to work :
using ffmpeg cmds :

  


  
        cmd2 = r'{} -ss "{}" -i "{}" -codec copy -timecode "{}" "{}"'.format(
            FFMPEG_PATH,
            abs(tc_diff_in_seconds),
            audio_path,
            "17074647",
            out_path
        )


  


  and also using pydub :

  


          current_audio = AudioSegment.from_wav("{}".format(audio_path))
        start_time_in_milli = abs(tc_diff_in_seconds*1000)
        end_time_in_milli = start_time_in_milli + video_dur_in_seconds * 1000
        trimmed_audio = current_audio[start_time_in_milli:end_time_in_milli]
        trimmed_audio.export('{}'.format(out_path), format='WAV', parameters=["-timecode", "17:07:46:47"])


  


  Any thoughts/suggestions welcome ! Thanks