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• Efficiently streaming a remote file into ffmpeg

  17 janvier 2016, par YZats

  My use case requires transcoding a remote MOV file that can’t be stored locally. I was hoping to use http protocol to stream the file into ffmpeg. This works, but I’m observing this to be a very expensive operation with (seemingly) redundant network traffic, so am looking for suggestions.

  What I see is that ffmpeg starts out with a Range request “0-“ (which brings in the entire file), followed by a number of open-ended requests (no ending offset) at different positions, each of which makes the http server return large chunks of the file again and again, from the starting position to the very end.

  For example, http range requests for a short 10MB file look like this :

  bytes=0-   
  
  bytes=10947419-
  
  bytes=36-
  
  bytes=3153008-
  
  bytes=5876422-

  Is there another input method that would be more network-efficient for my use case ? I control the server where the video file resides, so I’m flexible in what code runs there.

  Any help is greatly appreciated

• Loading a remote file into ffmpeg efficiently

  17 janvier 2016, par YZats

  My use case requires transcoding a remote MOV file that can’t be stored locally. I was hoping to use http protocol to stream the file into ffmpeg. This works, but I’m observing this to be a very expensive operation with (seemingly) redundant network traffic, so am looking for suggestions.

  What I see is that ffmpeg starts out with a Range request “0-“ (which brings in the entire file), followed by a number of open-ended requests (no ending offset) at different positions, each of which makes the http server return large chunks of the file again and again, from the starting position to the very end.

  For example, http range requests for a short 10MB file look like this :

  bytes=0-   
  
  bytes=10947419-
  
  bytes=36-
  
  bytes=3153008-
  
  bytes=5876422-

  Is there another input method that would be more network-efficient for my use case ? I control the server where the video file resides, so I’m flexible in what code runs there.

  Any help is greatly appreciated

• How to change volume of an audio AVPacket

  4 janvier 2013, par Saptarshi Biswas

  I have a desktop Qt-based application that fetches a sound stream from the network and plays it using QAudioOutput. I want to provide a volume control to the user so that he can reduce the volume. My code looks like this :

  float volume_control = get_user_pref(); // user provided volume level {0.0,1.0}
  
  
  
  for (;;) {
  
      AVPacket *retrieved_pkt = get_decoded_packet_stream();  // from network stream
  
  
  
      AVPacket *work_pkt
  
         = change_volume(retrieved_pkt, volume_control); // this is what I need
  
  
  
      // remaining code to play the work_pkt ...
  
  }

  How do I implement change_volume() or is there any off the shelf function that I can use ?

  Edit : Adding codec-related info as requested in the comments

  QAudioFormat format;
  
  format.setFrequency(44100);
  
  format.setChannels(2);
  
  format.setSampleSize(16);
  
  format.setCodec("audio/pcm");
  
  format.setByteOrder(QAudioFormat::LittleEndian);
  
  format.setSampleType(QAudioFormat::SignedInt);