Module: DSP::Dct

Defined in:
lib/dsprb/dct.rb,
sig/dsprb.rbs

Class Method Summary collapse

Class Method Details

.two(values, count) ⇒ ::Array[::Float]

Unnormalized DCT-II: X = sum_i x cos(pi k (i + 1/2) / N).

Parameters:

  • (::Array[::Numeric])
  • (::Integer)

Returns:

  • (::Array[::Float])

Raises:

  • (ArgumentError) 


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# File 'lib/dsprb/dct.rb', line 8

def two(values, count)
  length = values.length
  raise ArgumentError, "count must be positive, got #{count}" unless count.positive?

  Array.new(count) do |coefficient|
    total = 0.0
    index = 0
    while index < length
      total += values[index] * Math.cos(Math::PI * coefficient * (index + 0.5) / length)
      index += 1
    end

    total
  end
end