Class: Feep::SoundFile

Inherits:
Object
  • Object
show all
Defined in:
lib/feep/sound_file.rb

Instance Method Summary collapse

Instance Method Details

#create_sound(frequency, samples, output_filename, options) ⇒ Object 



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# File 'lib/feep/sound_file.rb', line 11

def create_sound(frequency, samples, output_filename, options)
  # Generate sample data for the given frequency, amplitude, and duration.
  # Since we are using a sample rate of 44,100Hz, 44,100 samples are required for one second of sound.
  samples = generate_sample_data(options[:waveform].to_sym, samples, frequency.to_f, options[:volume].to_f)

  # Wrap the array of samples in a Buffer, so that it can be written to a Wave file
  # by the WaveFile gem. Since we generated samples between -1.0 and 1.0, the sample
  # type should be :float
  buffer = WaveFile::Buffer.new(samples, WaveFile::Format.new(:mono, :float, 44100))

  # Write the Buffer containing our samples to a 16-bit, monophonic Wave file
  # with a sample rate of 44,100Hz, using the WaveFile gem.
  WaveFile::Writer.new(output_filename, WaveFile::Format.new(:mono, :pcm_16, 44100)) do |writer|
    writer.write(buffer)
  end
end

#generate_sample_data(wave_type, num_samples, frequency, max_amplitude) ⇒ Object 



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# File 'lib/feep/sound_file.rb', line 28

def generate_sample_data(wave_type, num_samples, frequency, max_amplitude)
  position_in_period = 0.0
  position_in_period_delta = frequency / SAMPLE_RATE

  # Initialize an array of samples set to 0.0. Each sample will be replaced with
  # an actual value below.
  samples = [].fill(0.0, 0, num_samples)

  num_samples.times do |i|
    # Add next sample to sample list. The sample value is determined by
    # plugging position_in_period into the appropriate wave function.
    if wave_type == :sine
      samples[i] = Math::sin(position_in_period * TWO_PI) * max_amplitude
    elsif wave_type == :square
      samples[i] = (position_in_period >= 0.5) ? max_amplitude : -max_amplitude
    elsif wave_type == :saw
      samples[i] = ((position_in_period * 2.0) - 1.0) * max_amplitude
    elsif wave_type == :triangle
      samples[i] = max_amplitude - (((position_in_period * 2.0) - 1.0) * max_amplitude * 2.0).abs
    elsif wave_type == :noise
      samples[i] = RANDOM_GENERATOR.rand(-max_amplitude..max_amplitude)
    end

    position_in_period += position_in_period_delta
    
    # Constrain the period between 0.0 and 1.0.
    # That is, keep looping and re-looping over the same period.
    if(position_in_period >= 1.0)
      position_in_period -= 1.0
    end
  end
  
  return samples
end