Multi Band Processor

Robert Jeffares <jeffares.robert@xxxxxxxxx> · Sun, 11 Apr 2021 15:47:05 +1200



    Hi all,
    I spent a very long
      time trying to get the multi band processor shown
      in man sox to work.
    It seems the manual
      is older then the code which has changed.
    I needed a
      processor
      that would take audio from various not so great sources, adjust
      the
      dynamic range to suit a talk radio stream, and try and correct the
      frequency balance. One source consistently has poor room
      acoustics.
      Another has levels that vary wildly and a range of audio frequency
      bandwidths.
    compand works as
      advertised. Perhaps not that clearly.
    mcompand does not
      work as implied. It does some of what mcompand does but not all.
    The manual could do
      with a makeover. Happy to help but I only know what the code does
      by
      trial and error so there may be stuff in there I have missed.
    This code works,
      and
      I share it in the interest of others in like situations looking
      for a
      sledge hammer to fix bad audio or a way to try and make the audio
      sound consistent. This is a SPEECH processor. Do not use it for
      music!
    I would encourage
      comments suggestions and improvements.
    I also have sox
      putting an intro and outro on the processed audio using splice so
      that items are produced complete. This is just the processing
      engine.
    

    ============================
      snip
      ======================================
    #! /bin/bash
    

     # the
      delay option is not available when mcompand is called by sox
     # doing
      this as a function makes it easy to switch on and off
    function bandmod {
     sox -V leveled.wav
      mcompanded.wav mcompand\
     "$f1_process"
      $f1_crossover\
     "$f2_process"
      $f2_crossover\
     "$f3_process"
      $f3_crossover\
     "$f4_process"
      $f4_crossover\
     "$f5_process"
      $f5_crossover\
     "$f6_process"
      $f6_crossover\
     "0,0.8
      -38,-38,-28,-28,-0,-6" gain 10 highpass 22 highpass
      22 sinc -n 255 -b 16 -12000
     }
    

    # set up band pass
      processing
    

    #first band
    f1_crossover='120'
    f1_process='0,0.8
      -60,-60,-48,-24,-24,-6,-12,-1.5,-6,-0.3 -21 -15'
    #
      attack1,decay1{,attack2,decay2}
      [soft-knee-dB:]in-dB1[,out-dB1]{,in-dB2,out-dB2} [gain
      [initial-volume-dB [delay]]]
    

    #second band
    f2_crossover='360'
    f2_process='0,0.8
      -60,-60,-48,-24,-24,-6,-12,-1.5,-6,-0.3 -9 -15'
    

    #third band
    f3_crossover='1080'
    f3_process='0,1.2
      -60,-60,-48,-24,-24,-6,-12,-1.5,-6,-0.3 -9 -15'
    

    #fourth band
    f4_crossover='3240'
    f4_process='0,1.2
      -60,-60,-48,-24,-24,-6,-12,-1.5,-6,-0.3 -9 -19'
    

    #fifth band
    f5_crossover='5000'
    f5_process='0,2.0
      -60,-60,-48,-24,-24,-6,-12,-1.5,-6,-0.3 -24 -19'
    

    #sixth band
    f6_crossover='10000'
    f6_process='0,1.8
      -60,-60,-48,-24,-24,-6,-12,-1.5,-6,-0.3 -48 -19'
    

    #for next loop
      makes
      it easy to set up for multiple files
    for i in $1
     do
     #take
      spaces out of filename
     newfile=$(mv "$i"
      "${i// /}")
     #now
      work with new name
     #get
      the filename for later use
    
      filename=$(basename $1)
     echo
      $filename
    
      filename="${filename%.*}"
     echo
      $filename
     #
      lets get the dynamic range sorted before band processing
     #
      files are processed as wav so there is no loss of quality 
     sox
      -V $newfile leveled.wav compand 0,1.2
      -60.1,-inf,-60,-160,-48,-24,-24,-6,-12,-1.5,-6,-0.3 -18 -6 
     sleep
      2
    

     bandmod
    

     # the
      processed audio replaces the original audio 
     mv
      mcompanded.wav $filename.wav
     rm
      leveled.wav
     done
    

    exit 0
    

    ============================
      snip
      ======================================
    

    regards
    Robert
    
      
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