Class: DSP::MelFilterbank

Inherits:
Object
  • Object
show all
Defined in:
lib/dsprb/mel_filterbank.rb,
sig/dsprb.rbs

Defined Under Namespace

Classes: Band

Constant Summary collapse

DEFAULT_FILTERS =

Returns:

  • (::Integer) 
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DEFAULT_LOW_HZ =

Returns:

  • (::Float) 
50.0
ENERGY_FLOOR =

Keeps the logarithm of a band that collected no energy finite.

Returns:

  • (::Float) 
1e-12

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(sample_rate:, size:, filters: DEFAULT_FILTERS, low: DEFAULT_LOW_HZ, high: nil, warp: 1.0) ⇒ MelFilterbank

warp rescales the band centers for vocal tract length normalization: values above 1 shift the bank upwards, suiting shorter vocal tracts.



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# File 'lib/dsprb/mel_filterbank.rb', line 19

def initialize(sample_rate:, size:, filters: DEFAULT_FILTERS, low: DEFAULT_LOW_HZ, high: nil, warp: 1.0)
  @sample_rate = Float(sample_rate)
  @size = Integer(size)
  @filters = Integer(filters)
  @low = Float(low)
  @high = Float(high || (@sample_rate / 2.0))
  @warp = Float(warp)

  validate!
  @bands = build_bands.freeze
  freeze
end

Instance Attribute Details

#bands ⇒ ::Array[Band] (readonly)

Returns the value of attribute bands.

Returns:



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# File 'lib/dsprb/mel_filterbank.rb', line 15

def bands
  @bands
end

#filters ⇒ ::Integer (readonly)

Returns the value of attribute filters.

Returns:

  • (::Integer) 


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# File 'lib/dsprb/mel_filterbank.rb', line 15

def filters
  @filters
end

#high ⇒ ::Float (readonly)

Returns the value of attribute high.

Returns:

  • (::Float) 


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# File 'lib/dsprb/mel_filterbank.rb', line 15

def high
  @high
end

#low ⇒ ::Float (readonly)

Returns the value of attribute low.

Returns:

  • (::Float) 


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# File 'lib/dsprb/mel_filterbank.rb', line 15

def low
  @low
end

#sample_rate ⇒ ::Float (readonly)

Returns the value of attribute sample_rate.

Returns:

  • (::Float) 


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# File 'lib/dsprb/mel_filterbank.rb', line 15

def sample_rate
  @sample_rate
end

#size ⇒ ::Integer (readonly)

Returns the value of attribute size.

Returns:

  • (::Integer) 


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# File 'lib/dsprb/mel_filterbank.rb', line 15

def size
  @size
end

#warp ⇒ ::Float (readonly)

Returns the value of attribute warp.

Returns:

  • (::Float) 


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# File 'lib/dsprb/mel_filterbank.rb', line 15

def warp
  @warp
end

Instance Method Details

#center_frequencies ⇒ ::Array[::Float]

Returns:

  • (::Array[::Float]) 


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# File 'lib/dsprb/mel_filterbank.rb', line 49

def center_frequencies = @centers

#energies(power) ⇒ ::Array[::Float]

Parameters:

  • (spectrum)

Returns:

  • (::Array[::Float]) 


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# File 'lib/dsprb/mel_filterbank.rb', line 32

def energies(power)
  @bands.map do |band|
    weights = band.weights
    offset = band.offset
    total = 0.0
    index = 0
    while index < weights.length
      total += weights[index] * power[offset + index]
      index += 1
    end

    total
  end
end

#log_energies(power) ⇒ ::Array[::Float]

Parameters:

  • (spectrum)

Returns:

  • (::Array[::Float]) 


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# File 'lib/dsprb/mel_filterbank.rb', line 47

def log_energies(power) = energies(power).map { |value| Math.log([value, ENERGY_FLOOR].max) }