Class: IIRFilter

Inherits:
Object
  • Object
show all
Defined in:
lib/Loudness/IIRFilter/IIRFilter.rb

Overview

IIR filter implementation

Direct Known Subclasses

PREFilter, RLBFilter

Instance Method Summary collapse

Constructor Details

#initialize(order) ⇒ IIRFilter

Returns a new instance of IIRFilter.



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# File 'lib/Loudness/IIRFilter/IIRFilter.rb', line 6

def initialize(order)
  @OldSamples = nil
  @ACoefs= nil
  @BCoefs= nil
  @Order = 0

  @Order = order 
  
  @OldSamples = Array.new(@Order) {0.0}
      
end

Instance Method Details

#FilterSample(sampleIn) ⇒ Float

Set IIR filter coeficients

Parameters:

  • bsampleIn (Float) —

    enters a new sample to filter

Returns:

  • (Float) —

    the output filtered sample



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# File 'lib/Loudness/IIRFilter/IIRFilter.rb', line 37

def FilterSample (sampleIn)
  
  nFilterCoefs = @Order + 1;
  sx = sampleIn;
  spx = 0.0;   
  ox = 0.0;   
  
  #A coefs
  nA = 0; 
  while nA < nFilterCoefs do
    if (nA == 0)
      spx = sx.to_f;
    else
      spx = spx.to_f -  @ACoefs[nA].to_f * @OldSamples[nA - 1].to_f  #Spx - m_pACoefs[nA]*m_pOldSamples[nA-1];
    end
  
    nA = nA + 1  
  end       
  
  #B coefs
  nB = 0;  
  while nB < nFilterCoefs do
    if (nB == 0)
      ox = ox.to_f + @BCoefs[nB].to_f * spx.to_f   #Ox = Ox + m_pBCoefs[nB]*Spx;
    else
      ox = ox.to_f + @BCoefs[nB].to_f * @OldSamples[nB - 1].to_f   #Ox = Ox + m_pBCoefs[nB]*m_pOldSamples[nB-1];
    end
  
    nB = nB + 1  
  end       
  
  #Set Old samples
  nS = @Order     
  while nS > 0 do
    if ((nS - 2) < 0)
      @OldSamples[nS - 1] = spx.to_f
    else
      @OldSamples[nS - 1] = @OldSamples[nS - 2].to_f    
    end       
    
    nS = nS - 1
  end

  return ox
end

#Info ⇒ String

Gets filter information

Returns:

  • (String) —

    filter information



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# File 'lib/Loudness/IIRFilter/IIRFilter.rb', line 85

def Info
  return "IIR Filter Order #{@Order}\nACoefs #{@ACoefs}\nBCoefs #{@BCoefs}\n"
end

#SetCoefs(b, a) ⇒ Object

Set IIR filter coeficients

Parameters:

  • b (Array) —

    sets the B coeficients of IIR filter example: [1.02, 0.99]

  • a (Array) —

    sets the A coeficients of IIR filter example: [1.02, 0.99]



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# File 'lib/Loudness/IIRFilter/IIRFilter.rb', line 21

def SetCoefs (b, a)
  if ((a.kind_of?(Array) == false) or (b.kind_of?(Array) == false))
    raise 'Filter coeficinets must be an array'
  end
  if ((a.length != @Order + 1) or (b.length != @Order + 1))
    raise "Incorrect number of coeficients. A filter of order #{@Order} must have #{@Order+1} coeficients"
  end
  
  @ACoefs = a
  @BCoefs = b
   
end