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• mute audio if the volume *exceeds* a threshold

  15 février 2023, par a1s2d3f4

  So, I have spent quite a bit of time looking for the answer but I get the exact opposite (something I already know how to do), namely, the audio below a certain threshold can get muted (can be done either with ffmpeg or sox).

  


  What I need is for the command to search my audio for anything that exceeds -18dB and mute all such segments. (The reason for this is because I have a recording where I am playing an electric piano with the audio output being recorded directly through the cable, but I am also recording from two microphones what I am speaking - between my playing. When I am playing the keyboard, the mics pick up a lot of action noise which I want to mute, and that's easy to do because the channel that records my piano input has piano sounds at that point and that corresponds exactly with when I want the audio from my mics to be muted, or at least attenuated.)

  


  Does anyone know if such a feat is possible ?
If it cannot be done with just one command, that's fine I'll try anything.

  


• How to Remove Hard Subtitles in a video file using ffmpeg ? [migrated]

  23 mars 2021, par xinYapeng

  I use the follow code to cover Hard Subtitle, but it is a little effective.

  


  ffmpeg -i in.mp4 -strict -2 -vf delogo=x=x:y=y:w=w:h=h:show=0 out.mp4


  


  The out.mp4 is a little mosaic somewhere.

  


  in.mp4 just has video stream and audio stream, NO subtitle steam.

  


  How to remove subtitle from in.mp4 using ffmpeg ?

  


  Thank you.

  


• Build Live Audio Stream Player

  5 décembre 2011, par Kurt

  For an internship project i've been trying to develop a simple audio player for audio live stream.

  Currently i'm using a homemade three buffering (of 1/3 s each) solution played by QAudioOutput, which recall himself after finished his reading.

  void VideoServer::getBuf(QBuffer * p_buf)
  
  {
  
      audio_chunk*    ac = NULL;
  
      std::vector v;
  
  
  
      v.clear();
  
      for (int i = 0; i < 20;)
  
      {
  
          ac = _audioPreviewSharedData->deQueueAudio();
  
          if (ac)
  
          {
  
              v.insert(v.end(), ac->v_buf.begin(), ac->v_buf.end());
  
              i++;
  
              delete ac;
  
          }
  
          else
  
              usleep(50000);
  
      }
  
      p_buf->close();
  
      p_buf->setData((const char *)(&v[0]), v.size()*2);
  
      p_buf->open(QIODevice::ReadOnly);
  
  }

  -

  void VideoServer::slot_launchAudioPreviewBuffering()
  
  {
  
      getBuf(_buf1);
  
      getBuf(_buf2);
  
      _state = 2;
  
      connect(_audioPreviewTimer, SIGNAL(timeout()), this, SLOT(slot_audioPreviewBuffering()));
  
      _audioPreviewTimer->start(0);
  
      connect(_audioOut, SIGNAL(stateChanged(QAudio::State)), this, SLOT(finishedPlaying(QAudio::State)));
  
  }

  -

  void VideoServer::finishedPlaying(QAudio::State state)
  
  {
  
      if(state == QAudio::IdleState) {
  
          slot_audioPreviewBuffering();
  
      }
  
  }

  -

  void VideoServer::slot_audioPreviewBuffering()
  
  {
  
      switch (_state) {
  
      case 0:
  
          {
  
              _audioOut->start(_buf2);
  
              getBuf(_buf1);
  
              _state = 1;
  
              break;
  
          }
  
      case 1:
  
          {
  
              _audioOut->start(_buf3);
  
              getBuf(_buf2);
  
              _state = 2;
  
              break;
  
          }
  
      case 2:
  
          {
  
              _audioOut->start(_buf1);
  
              getBuf(_buf3);
  
              _state = 0;
  
              break;
  
          }
  
      }
  
  }

  But i'm suffering of choppy sound (little interruption between audio chunk).

  How to play this flux without interruption () and with a reasonable delay between audio and video (less 1s) ? Is there a best way ? Am i doing wrong ?

  Thank you !