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• Revision 8bd88a3c83 : Merge "Make RTC coding flow support sub8x8 in key frame coding"

  10 décembre 2014, par Jingning Han

  Merge "Make RTC coding flow support sub8x8 in key frame coding"

• How to detect two identical audio/video files with different volume level ?

  3 juillet 2017, par Marina Rappoport

  I’m working on program that could compare 2 video files and show difference.
  I compare audio track of files using SOX and FFMPEG :

  1. invert one of the files (sox)
  2. merge other file and invert version of first (sox)
  3. detect silence (ffmpeg)

  But if two file differs only by volume level - all audio track will be detected as non-silent ranges.

  How to understand that 2 files have the same audio track, but with different volume level ?

  I tried to change sound level via sox : sox -v 1.1 input.wav output.wav
  And then compare statistical information (-n stat).
  It works fine. Result of division parameters audio2/audio1 :

      Samples read 1.00;
  
      Length (seconds) 1.00;
  
      Scaled by 1.00;
  
      Maximum amplitude 1.10;
  
      Minimum amplitude 1.10;
  
      Midline amplitude 1.10;
  
      Mean norm 1.10;
  
      Mean amplitude 1.00;
  
      RMS amplitude 1.10;
  
      Maximum delta 1.10;
  
      Mean delta 1.10;
  
      RMS delta 1.10;
  
      Rough frequency 1.00;
  
      Volume adjustment 1/1.10;

  BUT ! When I tried ffmpeg to change volume of video : ffmpeg -i input.mp4 -vcodec copy -af "volume=10dB" output.mp4 (or volume=volume=0.5) and than compared sox audio statistic : I can’t find any patterns...

  Samples read    1.00
  
  Length (seconds)    1.00
  
  Scaled by   1.00
  
  Maximum amplitude   0.71
  
  Minimum amplitude   0.64
  
  Midline amplitude   -2401.73
  
  Mean    norm    0.34
  
  Mean    amplitude   0.50
  
  RMS     amplitude   0.36
  
  Maximum delta   0.37
  
  Mean    delta   0.34
  
  RMS     delta   0.36
  
  Rough   frequency   0.99
  
  Volume adjustment   0.71

  I will be grateful for any ideas and help.

• Dynamic volume mixing with FFMPeg

  1er juin 2021, par jvhang

  I am streaming audio using FFMPeg and need to mix two audio sources using FFMpeg and set the volume level dynamically. I.e. once the stream starts, I need to be able update the ratio of the two volumes.

  


  Currently, I have the volume mixing and streaming working using the CLI version of FFMPeg but the volume mix ratio is static.

  


  Is there a way to dynamically set the volume ratio using the CLI tool ? Perhaps something with an FFMpeg expression ?

  


  Or is using the API the only option ? If so, can anyone point me towards an example of dynamically mixing audio ? I haven't been able to find one.

  


  Edit : here are the params I currently pass to mix audio. Again, this works fine, so not including the log as there is no error to fix. The question is how can I adjust the ratio of the amix mix after the process has launched. Willing to use the API if need be.

  


                  "-f rawvideo" + // container
                " -vcodec rawvideo" + // codec
                " -s " + width + "x" + height + // input video size, must be correct
                " -pix_fmt rgba" + // pixel format
                " -framerate " + frameRate +
                " -i pipe:0" + // from stdin in via pipe
               " -f dshow" +
                " -i audio=\"Stereo Mix (Realtek(R) Audio)\"" + //
                " -f dshow" +
                " -i audio=\"Microphone Array (Xbox NUI Sensor)\"" + // 
                " -filter_complex \"amix\"" +  // mix the two inputs, can added ratio if needed
                " -c:v libx264" + // x264 software encoder
                " -g " + frameRate *2 +
                " -keyint_min " + frameRate +
                " -c:a aac" + // audio format
                " -b:v 6M -maxrate 2M -bufsize 1M" + // constrain bitrate per twitch
                " -f flv" +
                " " + address 
            );