Module: Muze::Feature

Defined in:
lib/muze/feature/mfcc.rb,
lib/muze/feature/chroma.rb,
lib/muze/feature/context.rb,
lib/muze/feature/spectral.rb,
lib/muze/feature/aggregation.rb

Overview

Feature extraction methods.

Defined Under Namespace

Classes: Context

Class Method Summary collapse

Class Method Details

.beat_sync(data, beats:, aggregate: :mean) ⇒ Object

Beat-synchronous aggregation over the frame axis.

Raises:



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# File 'lib/muze/feature/aggregation.rb', line 8

def beat_sync(data, beats:, aggregate: :mean)
  raise Muze::ParameterError, "aggregate must be :mean, :median, or :max" unless %i[mean median max].include?(aggregate)

  matrix = Numo::SFloat.cast(data)
  matrix = matrix.expand_dims(0) if matrix.ndim == 1
  raise Muze::ParameterError, "data must be one- or two-dimensional" unless [1, 2].include?(matrix.ndim)

  rows, frames = matrix.shape
  boundaries = beat_boundaries(beats, frames)
  output = Numo::SFloat.zeros(rows, boundaries.length - 1)

  boundaries.each_cons(2).with_index do |(left, right), segment_index|
    rows.times do |row|
      values = matrix[row, left...right].to_a
      output[row, segment_index] = aggregate_values(values, aggregate:)
    end
  end

  output
end

.chroma_stft(y: nil, sr: 22_050, s: nil, n_chroma: 12, n_fft: 2048, hop_length: 512, norm: 2, tuning: 0.0, ctroct: nil, octwidth: nil) ⇒ Numo::SFloat

Returns shape: [n_chroma, frames].

Parameters:

  • y (Numo::SFloat, Array<Float>, nil) (defaults to: nil)
  • sr (Integer) (defaults to: 22_050)
  • s (Numo::SFloat, nil) (defaults to: nil)
  • n_chroma (Integer) (defaults to: 12)
  • n_fft (Integer) (defaults to: 2048)
  • hop_length (Integer) (defaults to: 512)
  • norm (Integer, nil) (defaults to: 2)
  • tuning (Float) (defaults to: 0.0)

Returns:

  • (Numo::SFloat) —

    shape: [n_chroma, frames]



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# File 'lib/muze/feature/chroma.rb', line 16

def chroma_stft(y: nil, sr: 22_050, s: nil, n_chroma: 12, n_fft: 2048, hop_length: 512, norm: 2, tuning: 0.0, ctroct: nil, octwidth: nil)
  spectrum = if s
               provided = Numo::SFloat.cast(s)
               validate_spectrum!(provided)
               provided
             else
               stft_matrix = Muze.stft(y, n_fft:, hop_length:)
               magnitude, = Muze.magphase(stft_matrix)
               magnitude
  end

  spectrum = spectrum.expand_dims(1) if spectrum.ndim == 1
  filter_bank = Muze::Filters.chroma(sr:, n_fft:, n_chroma:, tuning:, ctroct:, octwidth:)
  chroma = Muze::Core::Matrix.multiply(filter_bank, spectrum)
  normalize(chroma, norm:)
end

.context(y:, sr: 22_050, n_fft: 2048, hop_length: 512, center: true, pad_mode: :reflect) ⇒ Object 



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# File 'lib/muze/feature/context.rb', line 73

def context(y:, sr: 22_050, n_fft: 2048, hop_length: 512, center: true, pad_mode: :reflect)
  Context.new(y:, sr:, n_fft:, hop_length:, center:, pad_mode:)
end

.delta(data, order: 1, width: 9, mode: :interp) ⇒ Numo::SFloat

Parameters:

  • data (Numo::SFloat)
  • order (Integer) (defaults to: 1)
  • width (Integer) (defaults to: 9)
  • mode (Symbol) (defaults to: :interp)

Returns:

  • (Numo::SFloat)

Raises:



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# File 'lib/muze/feature/mfcc.rb', line 80

def delta(data, order: 1, width: 9, mode: :interp)
  raise Muze::ParameterError, "order must be >= 1" unless order >= 1
  raise Muze::ParameterError, "width must be odd and >= 3" unless width.odd? && width >= 3
  raise Muze::ParameterError, "mode must be :interp, :nearest, :mirror, or :constant" unless %i[interp nearest mirror constant].include?(mode)

  result = Numo::SFloat.cast(data)
  original_ndim = result.ndim
  order.times { result = finite_difference(result, width, mode:) }
  result = result[true, 0] if original_ndim == 1 && result.ndim == 2
  result
end

.extract(y:, sr: 22_050, features: Context::DEFAULT_FEATURES, n_fft: 2048, hop_length: 512, center: true, pad_mode: :reflect) ⇒ Object 



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# File 'lib/muze/feature/context.rb', line 77

def extract(y:, sr: 22_050, features: Context::DEFAULT_FEATURES, n_fft: 2048, hop_length: 512, center: true, pad_mode: :reflect)
  context(y:, sr:, n_fft:, hop_length:, center:, pad_mode:).extract(features:)
end

.melspectrogram(y: nil, sr: 22_050, s: nil, n_fft: 2048, hop_length: 512, n_mels: 128, fmin: 0.0, fmax: nil, power: 2.0, center: true, window: :hann, pad_mode: :reflect, norm: nil, s_kind: :power) ⇒ Numo::SFloat

Parameters:

  • y (Numo::SFloat, Array<Float>, nil) (defaults to: nil)
  • sr (Integer) (defaults to: 22_050)
  • s (Numo::SFloat, nil) (defaults to: nil)
  • n_fft (Integer) (defaults to: 2048)
  • hop_length (Integer) (defaults to: 512)
  • n_mels (Integer) (defaults to: 128)
  • fmin (Float) (defaults to: 0.0)
  • fmax (Float, nil) (defaults to: nil)
  • power (Float) (defaults to: 2.0)
  • center (Boolean) (defaults to: true)
  • window (Symbol) (defaults to: :hann)
  • pad_mode (Symbol) (defaults to: :reflect)
  • norm (Symbol, nil) (defaults to: nil)

Returns:

  • (Numo::SFloat)

Raises:



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# File 'lib/muze/feature/mfcc.rb', line 22

def melspectrogram(y: nil, sr: 22_050, s: nil, n_fft: 2048, hop_length: 512, n_mels: 128, fmin: 0.0, fmax: nil, power: 2.0, center: true, window: :hann, pad_mode: :reflect, norm: nil, s_kind: :power)
  raise Muze::ParameterError, "power must be positive" unless power.positive?
  raise Muze::ParameterError, "s_kind must be :power or :magnitude" unless %i[power magnitude].include?(s_kind)

  spectrum = if s
               provided = Numo::SFloat.cast(s)
               validate_finite_array!(provided.to_a.flatten, "s")
               raise Muze::ParameterError, "spectrogram input must be non-negative" if provided.to_a.flatten.any?(&:negative?)

               s_kind == :magnitude ? (provided**power).cast_to(Numo::SFloat) : provided
             else
               spectrogram(y, n_fft:, hop_length:, power:, center:, window:, pad_mode:)
             end
  filter_bank = Muze::Filters.mel(sr:, n_fft:, n_mels:, fmin:, fmax:, norm:)
  Muze::Core::Matrix.multiply(filter_bank, spectrum)
end

.mfcc(y: nil, sr: 22_050, s: nil, n_mfcc: 20, n_fft: 2048, hop_length: 512, n_mels: 128, fmin: 0.0, fmax: nil, dct_type: 2, lifter: 0, norm: :ortho, s_kind: :mel_power) ⇒ Numo::SFloat

Parameters:

  • y (Numo::SFloat, Array<Float>, nil) (defaults to: nil)
  • sr (Integer) (defaults to: 22_050)
  • s (Numo::SFloat, nil) (defaults to: nil)
  • n_mfcc (Integer) (defaults to: 20)
  • n_fft (Integer) (defaults to: 2048)
  • hop_length (Integer) (defaults to: 512)
  • n_mels (Integer) (defaults to: 128)
  • fmin (Float) (defaults to: 0.0)
  • fmax (Float, nil) (defaults to: nil)
  • dct_type (Integer) (defaults to: 2)
  • lifter (Integer) (defaults to: 0)
  • norm (Symbol, nil) (defaults to: :ortho)

Returns:

  • (Numo::SFloat)

Raises:



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# File 'lib/muze/feature/mfcc.rb', line 52

def mfcc(y: nil, sr: 22_050, s: nil, n_mfcc: 20, n_fft: 2048, hop_length: 512, n_mels: 128, fmin: 0.0, fmax: nil, dct_type: 2, lifter: 0, norm: :ortho, s_kind: :mel_power)
  raise Muze::ParameterError, "n_mfcc must be positive" unless n_mfcc.positive?
  raise Muze::ParameterError, "lifter must be >= 0" if lifter.negative?
  raise Muze::ParameterError, "s_kind must be :mel_power or :log_mel" unless %i[mel_power log_mel].include?(s_kind)

  mel_spec = if s
               provided = Numo::SFloat.cast(s)
               validate_finite_array!(provided.to_a.flatten, "s")
               if s_kind == :mel_power && provided.to_a.flatten.any?(&:negative?)
                 raise Muze::ParameterError, "mel power spectrogram must be non-negative"
               end

               provided
             else
               melspectrogram(y:, sr:, n_fft:, hop_length:, n_mels:, fmin:, fmax:)
             end

  log_mel = s_kind == :log_mel ? mel_spec : Muze.power_to_db(mel_spec)
  dct = Muze::Core::DCT.dct(log_mel, type: dct_type, axis: 0, norm:)
  coeffs = dct[0...n_mfcc, true].cast_to(Numo::SFloat)
  apply_lifter(coeffs, lifter:)
end

.poly_features(y: nil, s: nil, sr: 22_050, n_fft: 2048, hop_length: 512, order: 1, frequency: nil, center: true, pad_mode: :reflect, s_kind: :magnitude) ⇒ Numo::SFloat

Returns shape: [order + 1, frames].

Returns:

  • (Numo::SFloat) —

    shape: [order + 1, frames]

Raises:



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# File 'lib/muze/feature/spectral.rb', line 255

def poly_features(y: nil, s: nil, sr: 22_050, n_fft: 2048, hop_length: 512, order: 1, frequency: nil, center: true, pad_mode: :reflect, s_kind: :magnitude)
  raise Muze::ParameterError, "order must be >= 0" unless order.is_a?(Integer) && order >= 0

  magnitude, frequencies = prepare_magnitude(y:, s:, sr:, n_fft:, hop_length:, center:, pad_mode:, s_kind:)
  bins, frames = magnitude.shape
  x_values = frequency ? Numo::SFloat.cast(frequency).to_a.flatten : frequencies
  raise Muze::ParameterError, "frequency length must match spectrum bins" unless x_values.length == bins

  x_values = normalize_frequency_axis(x_values)
  output = Numo::SFloat.zeros(order + 1, frames)
  frames.times do |frame_index|
    coefficients = polynomial_coefficients(x_values, magnitude[true, frame_index].to_a, order)
    coefficients.each_with_index { |value, index| output[index, frame_index] = value }
  end

  output
end

.rms(y: nil, s: nil, frame_length: 2048, hop_length: 512, center: false) ⇒ Numo::SFloat

Returns shape: [1, frames].

Parameters:

  • y (Numo::SFloat, Array<Float>, nil) (defaults to: nil)
  • s (Numo::SFloat, nil) (defaults to: nil)
  • frame_length (Integer) (defaults to: 2048)
  • hop_length (Integer) (defaults to: 512)

Returns:

  • (Numo::SFloat) —

    shape: [1, frames]



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# File 'lib/muze/feature/spectral.rb', line 298

def rms(y: nil, s: nil, frame_length: 2048, hop_length: 512, center: false)
  if s
    matrix = Numo::SFloat.cast(s)
    validate_finite_array!(matrix.to_a.flatten, "s")
    matrix = matrix.expand_dims(1) if matrix.ndim == 1
    _, frames = matrix.shape
    values = Array.new(frames) do |frame_index|
      frame = matrix[true, frame_index]
      Math.sqrt((frame**2).sum / frame.size)
    end

    return Numo::SFloat[values].reshape(1, values.length)
  end

  signal = mono_signal_to_a(y, "y")
  signal = Array.new(frame_length / 2, 0.0) + signal + Array.new(frame_length / 2, 0.0) if center
  frames = Muze::Core::Frames.slice(signal, frame_length:, hop_length:)
  values = frames.map do |frame|
    Math.sqrt(frame.sum { |value| value * value } / frame.length)
  end

  Numo::SFloat[values].reshape(1, values.length)
end

.spectral_bandwidth(y: nil, s: nil, sr: 22_050, n_fft: 2048, hop_length: 512, p: 2, center: true, pad_mode: :reflect, s_kind: :magnitude) ⇒ Numo::SFloat

Returns shape: [1, frames].

Parameters:

  • y (Numo::SFloat, Array<Float>, nil) (defaults to: nil)
  • s (Numo::SFloat, nil) (defaults to: nil)
  • sr (Integer) (defaults to: 22_050)
  • n_fft (Integer) (defaults to: 2048)
  • hop_length (Integer) (defaults to: 512)
  • p (Integer) (defaults to: 2)

Returns:

  • (Numo::SFloat) —

    shape: [1, frames]

Raises:



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# File 'lib/muze/feature/spectral.rb', line 41

def spectral_bandwidth(y: nil, s: nil, sr: 22_050, n_fft: 2048, hop_length: 512, p: 2, center: true, pad_mode: :reflect, s_kind: :magnitude)
  raise Muze::ParameterError, "p must be positive" unless p.positive?

  magnitude, frequencies = prepare_magnitude(y:, s:, sr:, n_fft:, hop_length:, center:, pad_mode:, s_kind:)
  centroids = spectral_centroid(y:, s: magnitude, sr:, n_fft:, hop_length:, center:, pad_mode:, s_kind: :magnitude)
  _, frames = magnitude.shape
  output = Numo::SFloat.zeros(1, frames)

  frames.times do |frame_index|
    spectrum = magnitude[true, frame_index]
    denominator = spectrum.sum
    if denominator <= 0.0
      output[0, frame_index] = 0.0
      next
    end

    sum = 0.0
    frequencies.length.times do |bin|
      distance = (frequencies[bin] - centroids[0, frame_index]).abs
      sum += spectrum[bin] * (distance**p)
    end

    output[0, frame_index] = (sum / denominator)**(1.0 / p)
  end

  output
end

.spectral_centroid(y: nil, s: nil, sr: 22_050, n_fft: 2048, hop_length: 512, center: true, pad_mode: :reflect, s_kind: :magnitude) ⇒ Numo::SFloat

Returns shape: [1, frames].

Parameters:

  • y (Numo::SFloat, Array<Float>, nil) (defaults to: nil)
  • s (Numo::SFloat, nil) (defaults to: nil)
  • sr (Integer) (defaults to: 22_050)
  • n_fft (Integer) (defaults to: 2048)
  • hop_length (Integer) (defaults to: 512)

Returns:

  • (Numo::SFloat) —

    shape: [1, frames]



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# File 'lib/muze/feature/spectral.rb', line 13

def spectral_centroid(y: nil, s: nil, sr: 22_050, n_fft: 2048, hop_length: 512, center: true, pad_mode: :reflect, s_kind: :magnitude)
  magnitude, frequencies = prepare_magnitude(y:, s:, sr:, n_fft:, hop_length:, center:, pad_mode:, s_kind:)
  _, frames = magnitude.shape
  output = Numo::SFloat.zeros(1, frames)

  frames.times do |frame_index|
    spectrum = magnitude[true, frame_index]
    denominator = spectrum.sum
    if denominator <= 0.0
      output[0, frame_index] = 0.0
      next
    end

    numerator = 0.0
    frequencies.length.times { |bin| numerator += frequencies[bin] * spectrum[bin] }
    output[0, frame_index] = numerator / denominator
  end

  output
end

.spectral_contrast(y: nil, s: nil, sr: 22_050, n_fft: 2048, hop_length: 512, n_bands: 6, quantile: 0.02, fmin: 200.0, center: true, pad_mode: :reflect, s_kind: :magnitude) ⇒ Numo::SFloat

Returns shape: [n_bands + 1, frames].

Parameters:

  • y (Numo::SFloat, Array<Float>, nil) (defaults to: nil)
  • s (Numo::SFloat, nil) (defaults to: nil)
  • n_bands (Integer) (defaults to: 6)
  • quantile (Float) (defaults to: 0.02)

Returns:

  • (Numo::SFloat) —

    shape: [n_bands + 1, frames]

Raises:



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# File 'lib/muze/feature/spectral.rb', line 129

def spectral_contrast(y: nil, s: nil, sr: 22_050, n_fft: 2048, hop_length: 512, n_bands: 6, quantile: 0.02, fmin: 200.0, center: true, pad_mode: :reflect, s_kind: :magnitude)
  raise Muze::ParameterError, "n_bands must be positive" unless n_bands.positive?
  raise Muze::ParameterError, "quantile must satisfy 0 < quantile < 0.5" unless quantile.positive? && quantile < 0.5
  raise Muze::ParameterError, "fmin must be positive" unless fmin.positive?

  magnitude, frequencies = prepare_magnitude(y:, s:, sr:, n_fft:, hop_length:, center:, pad_mode:, s_kind:)
  bins, frames = magnitude.shape
  edges = spectral_contrast_edges(frequencies, n_bands:, fmin:, sr:)
  output = Numo::SFloat.zeros(n_bands + 1, frames)

  (n_bands + 1).times do |band|
    lower = edges[band]
    upper = [edges[band + 1], lower + 1].max

    frames.times do |frame_index|
      segment = magnitude[lower...upper, frame_index].to_a.sort
      next if segment.empty?

      low_idx = [(segment.length * quantile).floor, segment.length - 1].min
      high_idx = [(segment.length * (1.0 - quantile)).floor, segment.length - 1].min
      valley = [segment[low_idx], 1.0e-10].max
      peak = [segment[high_idx], 1.0e-10].max
      output[band, frame_index] = 10.0 * Math.log10(peak / valley)
    end
  end

  output
end

.spectral_contrast_edges(frequencies, n_bands:, fmin:, sr:) ⇒ Array<Integer>

Returns:

  • (Array<Integer>) 


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# File 'lib/muze/feature/spectral.rb', line 159

def spectral_contrast_edges(frequencies, n_bands:, fmin:, sr:)
  nyquist = sr / 2.0
  hz_edges = [0.0, fmin]
  n_bands.times { |band| hz_edges << [fmin * (2.0**(band + 1)), nyquist].min }
  hz_edges << nyquist
  hz_edges.map do |hz|
    index = frequencies.each_index.min_by { |idx| (frequencies[idx] - hz).abs }
    [[index, 0].max, frequencies.length - 1].min
  end.each_cons(2).with_object([0]) do |(left, right), edges|
    edges << [right, left + 1].max
  end
end

.spectral_crest(y: nil, s: nil, sr: 22_050, n_fft: 2048, hop_length: 512, center: true, pad_mode: :reflect, s_kind: :magnitude) ⇒ Numo::SFloat

Returns shape: [1, frames].

Returns:

  • (Numo::SFloat) —

    shape: [1, frames]



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# File 'lib/muze/feature/spectral.rb', line 204

def spectral_crest(y: nil, s: nil, sr: 22_050, n_fft: 2048, hop_length: 512, center: true, pad_mode: :reflect, s_kind: :magnitude)
  magnitude, = prepare_magnitude(y:, s:, sr:, n_fft:, hop_length:, center:, pad_mode:, s_kind:)
  _, frames = magnitude.shape
  output = Numo::SFloat.zeros(1, frames)

  frames.times do |frame_index|
    spectrum = magnitude[true, frame_index]
    mean = spectrum.mean
    output[0, frame_index] = mean <= 0.0 ? 0.0 : spectrum.max / mean
  end
  output
end

.spectral_decrease(y: nil, s: nil, sr: 22_050, n_fft: 2048, hop_length: 512, center: true, pad_mode: :reflect, s_kind: :magnitude) ⇒ Numo::SFloat

Returns shape: [1, frames].

Returns:

  • (Numo::SFloat) —

    shape: [1, frames]



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# File 'lib/muze/feature/spectral.rb', line 235

def spectral_decrease(y: nil, s: nil, sr: 22_050, n_fft: 2048, hop_length: 512, center: true, pad_mode: :reflect, s_kind: :magnitude)
  magnitude, = prepare_magnitude(y:, s:, sr:, n_fft:, hop_length:, center:, pad_mode:, s_kind:)
  bins, frames = magnitude.shape
  output = Numo::SFloat.zeros(1, frames)

  frames.times do |frame_index|
    first = magnitude[0, frame_index]
    denominator = 0.0
    numerator = 0.0
    (1...bins).each do |bin|
      value = magnitude[bin, frame_index]
      numerator += (value - first) / bin
      denominator += value
    end
    output[0, frame_index] = denominator <= 0.0 ? 0.0 : numerator / denominator
  end
  output
end

.spectral_entropy(y: nil, s: nil, sr: 22_050, n_fft: 2048, hop_length: 512, center: true, pad_mode: :reflect, s_kind: :magnitude) ⇒ Numo::SFloat

Returns shape: [1, frames].

Returns:

  • (Numo::SFloat) —

    shape: [1, frames]



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# File 'lib/muze/feature/spectral.rb', line 186

def spectral_entropy(y: nil, s: nil, sr: 22_050, n_fft: 2048, hop_length: 512, center: true, pad_mode: :reflect, s_kind: :magnitude)
  magnitude, = prepare_magnitude(y:, s:, sr:, n_fft:, hop_length:, center:, pad_mode:, s_kind:)
  _, frames = magnitude.shape
  output = Numo::SFloat.zeros(1, frames)

  frames.times do |frame_index|
    spectrum = magnitude[true, frame_index]
    total = spectrum.sum
    next if total <= 0.0

    probs = spectrum / total
    entropy = probs.to_a.sum { |value| value.positive? ? -(value * Math.log2(value)) : 0.0 }
    output[0, frame_index] = entropy / Math.log2([spectrum.size, 2].max)
  end
  output
end

.spectral_flatness(y: nil, s: nil, n_fft: 2048, hop_length: 512, amin: 1.0e-10, center: true, pad_mode: :reflect, s_kind: :magnitude) ⇒ Numo::SFloat

Returns shape: [1, frames].

Parameters:

  • y (Numo::SFloat, Array<Float>, nil) (defaults to: nil)
  • s (Numo::SFloat, nil) (defaults to: nil)
  • amin (Float) (defaults to: 1.0e-10)

Returns:

  • (Numo::SFloat) —

    shape: [1, frames]

Raises:



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# File 'lib/muze/feature/spectral.rb', line 107

def spectral_flatness(y: nil, s: nil, n_fft: 2048, hop_length: 512, amin: 1.0e-10, center: true, pad_mode: :reflect, s_kind: :magnitude)
  raise Muze::ParameterError, "amin must be positive" unless amin.positive?

  magnitude, = prepare_magnitude(y:, s:, sr: 22_050, n_fft:, hop_length:, center:, pad_mode:, s_kind:)
  _, frames = magnitude.shape
  output = Numo::SFloat.zeros(1, frames)

  frames.times do |frame_index|
    spectrum = magnitude[true, frame_index].to_a.map { |value| [value, amin].max }
    geometric = Math.exp(spectrum.sum { |value| Math.log(value) } / spectrum.length)
    arithmetic = spectrum.sum(0.0) / spectrum.length
    output[0, frame_index] = geometric / arithmetic
  end

  output
end

.spectral_flux(y: nil, s: nil, sr: 22_050, n_fft: 2048, hop_length: 512, center: true, pad_mode: :reflect, s_kind: :magnitude) ⇒ Numo::SFloat

Returns shape: [1, frames].

Returns:

  • (Numo::SFloat) —

    shape: [1, frames]



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# File 'lib/muze/feature/spectral.rb', line 173

def spectral_flux(y: nil, s: nil, sr: 22_050, n_fft: 2048, hop_length: 512, center: true, pad_mode: :reflect, s_kind: :magnitude)
  magnitude, = prepare_magnitude(y:, s:, sr:, n_fft:, hop_length:, center:, pad_mode:, s_kind:)
  _, frames = magnitude.shape
  output = Numo::SFloat.zeros(1, frames)

  (1...frames).each do |frame_index|
    diff = magnitude[true, frame_index] - magnitude[true, frame_index - 1]
    output[0, frame_index] = Math.sqrt((diff * diff).sum)
  end
  output
end

.spectral_rolloff(y: nil, s: nil, sr: 22_050, n_fft: 2048, hop_length: 512, roll_percent: 0.85, center: true, pad_mode: :reflect, s_kind: :magnitude) ⇒ Numo::SFloat

Returns shape: [1, frames].

Parameters:

  • y (Numo::SFloat, Array<Float>, nil) (defaults to: nil)
  • s (Numo::SFloat, nil) (defaults to: nil)
  • sr (Integer) (defaults to: 22_050)
  • n_fft (Integer) (defaults to: 2048)
  • hop_length (Integer) (defaults to: 512)
  • roll_percent (Float) (defaults to: 0.85)

Returns:

  • (Numo::SFloat) —

    shape: [1, frames]

Raises:



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# File 'lib/muze/feature/spectral.rb', line 76

def spectral_rolloff(y: nil, s: nil, sr: 22_050, n_fft: 2048, hop_length: 512, roll_percent: 0.85, center: true, pad_mode: :reflect, s_kind: :magnitude)
  raise Muze::ParameterError, "roll_percent must satisfy 0 < roll_percent < 1" unless roll_percent.positive? && roll_percent < 1.0

  magnitude, frequencies = prepare_magnitude(y:, s:, sr:, n_fft:, hop_length:, center:, pad_mode:, s_kind:)
  _, frames = magnitude.shape
  output = Numo::SFloat.zeros(1, frames)

  frames.times do |frame_index|
    spectrum = magnitude[true, frame_index]
    threshold = spectrum.sum * roll_percent
    cumulative = 0.0
    rolloff_frequency = frequencies.last

    frequencies.length.times do |bin|
      cumulative += spectrum[bin]
      if cumulative >= threshold
        rolloff_frequency = frequencies[bin]
        break
      end
    end

    output[0, frame_index] = rolloff_frequency
  end

  output
end

.spectral_slope(y: nil, s: nil, sr: 22_050, n_fft: 2048, hop_length: 512, center: true, pad_mode: :reflect, s_kind: :magnitude) ⇒ Numo::SFloat

Returns shape: [1, frames].

Returns:

  • (Numo::SFloat) —

    shape: [1, frames]



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# File 'lib/muze/feature/spectral.rb', line 218

def spectral_slope(y: nil, s: nil, sr: 22_050, n_fft: 2048, hop_length: 512, center: true, pad_mode: :reflect, s_kind: :magnitude)
  magnitude, frequencies = prepare_magnitude(y:, s:, sr:, n_fft:, hop_length:, center:, pad_mode:, s_kind:)
  mean_frequency = frequencies.sum / frequencies.length.to_f
  frequency_variance = frequencies.sum { |frequency| (frequency - mean_frequency)**2 }
  _, frames = magnitude.shape
  output = Numo::SFloat.zeros(1, frames)

  frames.times do |frame_index|
    spectrum = magnitude[true, frame_index].to_a
    mean_spectrum = spectrum.sum / spectrum.length.to_f
    covariance = frequencies.each_with_index.sum { |frequency, idx| (frequency - mean_frequency) * (spectrum[idx] - mean_spectrum) }
    output[0, frame_index] = frequency_variance.zero? ? 0.0 : covariance / frequency_variance
  end
  output
end

.tempogram(y: nil, onset_envelope: nil, sr: 22_050, hop_length: 512, win_length: 384, normalize: false) ⇒ Numo::SFloat

Parameters:

  • y (Numo::SFloat, Array<Float>, nil) (defaults to: nil)
  • onset_envelope (Numo::SFloat, Array<Float>, nil) (defaults to: nil)
  • sr (Integer) (defaults to: 22_050)
  • hop_length (Integer) (defaults to: 512)
  • win_length (Integer) (defaults to: 384)

Returns:

  • (Numo::SFloat)

Raises:



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# File 'lib/muze/feature/spectral.rb', line 328

def tempogram(y: nil, onset_envelope: nil, sr: 22_050, hop_length: 512, win_length: 384, normalize: false)
  raise Muze::ParameterError, "sr must be a positive integer" unless sr.is_a?(Integer) && sr.positive?
  raise Muze::ParameterError, "hop_length must be a positive integer" unless hop_length.is_a?(Integer) && hop_length.positive?
  raise Muze::ParameterError, "win_length must be a positive integer" unless win_length.is_a?(Integer) && win_length.positive?
  raise Muze::ParameterError, "normalize must be true or false" unless [true, false].include?(normalize)

  envelope = if onset_envelope
               onset_envelope.is_a?(Numo::NArray) ? onset_envelope.to_a : Array(onset_envelope)
             else
               onset_env_from_signal(y, sr:, hop_length:)
             end
  validate_finite_array!(envelope, "onset_envelope")

  frames = envelope.length
  tempogram = Numo::SFloat.zeros(win_length, frames)

  frames.times do |frame_index|
    window_start = [0, frame_index - win_length + 1].max
    segment = envelope[window_start..frame_index]
    win_length.times do |lag|
      break if lag >= segment.length

      value = 0.0
      (lag...segment.length).each do |offset|
        value += segment[offset] * segment[offset - lag]
      end
      tempogram[lag, frame_index] = normalize ? normalized_autocorrelation(segment, lag, value) : value
    end
  end

  tempogram
end

.tonnetz(y: nil, chroma: nil, sr: 22_050, n_fft: 2048, hop_length: 512) ⇒ Numo::SFloat

Returns shape: [6, frames].

Returns:

  • (Numo::SFloat) —

    shape: [6, frames]

Raises:



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# File 'lib/muze/feature/chroma.rb', line 34

def tonnetz(y: nil, chroma: nil, sr: 22_050, n_fft: 2048, hop_length: 512)
  chroma_matrix = chroma ? Numo::SFloat.cast(chroma) : chroma_stft(y:, sr:, n_fft:, hop_length:)
  chroma_matrix = chroma_matrix.expand_dims(1) if chroma_matrix.ndim == 1
  validate_spectrum!(chroma_matrix)
  raise Muze::ParameterError, "tonnetz requires 12-bin chroma" unless chroma_matrix.shape[0] == 12

  frames = chroma_matrix.shape[1]
  output = Numo::SFloat.zeros(6, frames)
  intervals = [7, 7, 3, 3, 4, 4]
  phases = [0.0, Math::PI / 2.0, 0.0, Math::PI / 2.0, 0.0, Math::PI / 2.0]

  frames.times do |frame|
    vector = chroma_matrix[true, frame]
    total = vector.sum
    next if total <= 0.0

    normalized = vector / total
    6.times do |dimension|
      sum = 0.0
      12.times do |chroma_index|
        angle = ((Math::PI * intervals[dimension] * chroma_index) / 6.0) + phases[dimension]
        sum += normalized[chroma_index] * Math.cos(angle)
      end
      output[dimension, frame] = sum
    end
  end

  output
end

.zero_crossing_rate(y, frame_length: 2048, hop_length: 512, threshold: 0.0, center: false) ⇒ Numo::SFloat

Returns shape: [1, frames].

Parameters:

  • y (Numo::SFloat, Array<Float>)
  • frame_length (Integer) (defaults to: 2048)
  • hop_length (Integer) (defaults to: 512)

Returns:

  • (Numo::SFloat) —

    shape: [1, frames]

Raises:



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# File 'lib/muze/feature/spectral.rb', line 277

def zero_crossing_rate(y, frame_length: 2048, hop_length: 512, threshold: 0.0, center: false)
  raise Muze::ParameterError, "threshold must be >= 0" if threshold.negative?

  signal = mono_signal_to_a(y, "y")
  signal = Array.new(frame_length / 2, 0.0) + signal + Array.new(frame_length / 2, 0.0) if center
  frames = Muze::Core::Frames.slice(signal, frame_length:, hop_length:)
  values = frames.map do |frame|
    crossings = 0
    signs = frame.map { |value| value.abs <= threshold ? 0.0 : value }
    (1...signs.length).each { |idx| crossings += 1 if (signs[idx - 1] >= 0) != (signs[idx] >= 0) }
    crossings.to_f / frame_length
  end

  Numo::SFloat[values].reshape(1, values.length)
end