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""" |
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Each generator will return float samples from -1.0 to 1.0, which can be |
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converted to actual audio with 8, 16, 24, or 32 bit depth using the |
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SiganlGenerator.to_audio_segment() method (on any of it's subclasses). |
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See Wikipedia's "waveform" page for info on some of the generators included |
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here: http://en.wikipedia.org/wiki/Waveform |
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""" |
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import math |
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import array |
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import itertools |
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import random |
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from .audio_segment import AudioSegment |
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from .utils import ( |
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db_to_float, |
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get_frame_width, |
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get_array_type, |
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get_min_max_value |
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) |
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class SignalGenerator(object): |
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def __init__(self, sample_rate=44100, bit_depth=16): |
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self.sample_rate = sample_rate |
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self.bit_depth = bit_depth |
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def to_audio_segment(self, duration=1000.0, volume=0.0): |
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""" |
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Duration in milliseconds |
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(default: 1 second) |
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Volume in DB relative to maximum amplitude |
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(default 0.0 dBFS, which is the maximum value) |
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""" |
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minval, maxval = get_min_max_value(self.bit_depth) |
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sample_width = get_frame_width(self.bit_depth) |
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array_type = get_array_type(self.bit_depth) |
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gain = db_to_float(volume) |
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sample_count = int(self.sample_rate * (duration / 1000.0)) |
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sample_data = (int(val * maxval * gain) for val in self.generate()) |
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sample_data = itertools.islice(sample_data, 0, sample_count) |
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data = array.array(array_type, sample_data) |
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try: |
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data = data.tobytes() |
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except: |
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data = data.tostring() |
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return AudioSegment(data=data, metadata={ |
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"channels": 1, |
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"sample_width": sample_width, |
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"frame_rate": self.sample_rate, |
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"frame_width": sample_width, |
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}) |
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def generate(self): |
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raise NotImplementedError("SignalGenerator subclasses must implement the generate() method, and *should not* call the superclass implementation.") |
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class Sine(SignalGenerator): |
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def __init__(self, freq, **kwargs): |
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super(Sine, self).__init__(**kwargs) |
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self.freq = freq |
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def generate(self): |
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sine_of = (self.freq * 2 * math.pi) / self.sample_rate |
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sample_n = 0 |
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while True: |
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yield math.sin(sine_of * sample_n) |
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sample_n += 1 |
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class Pulse(SignalGenerator): |
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def __init__(self, freq, duty_cycle=0.5, **kwargs): |
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super(Pulse, self).__init__(**kwargs) |
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self.freq = freq |
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self.duty_cycle = duty_cycle |
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def generate(self): |
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sample_n = 0 |
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cycle_length = self.sample_rate / float(self.freq) |
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pulse_length = cycle_length * self.duty_cycle |
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while True: |
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if (sample_n % cycle_length) < pulse_length: |
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yield 1.0 |
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else: |
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yield -1.0 |
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sample_n += 1 |
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class Square(Pulse): |
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def __init__(self, freq, **kwargs): |
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kwargs['duty_cycle'] = 0.5 |
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super(Square, self).__init__(freq, **kwargs) |
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class Sawtooth(SignalGenerator): |
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def __init__(self, freq, duty_cycle=1.0, **kwargs): |
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super(Sawtooth, self).__init__(**kwargs) |
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self.freq = freq |
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self.duty_cycle = duty_cycle |
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def generate(self): |
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sample_n = 0 |
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cycle_length = self.sample_rate / float(self.freq) |
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midpoint = cycle_length * self.duty_cycle |
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ascend_length = midpoint |
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descend_length = cycle_length - ascend_length |
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while True: |
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cycle_position = sample_n % cycle_length |
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if cycle_position < midpoint: |
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yield (2 * cycle_position / ascend_length) - 1.0 |
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else: |
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yield 1.0 - (2 * (cycle_position - midpoint) / descend_length) |
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sample_n += 1 |
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class Triangle(Sawtooth): |
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def __init__(self, freq, **kwargs): |
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kwargs['duty_cycle'] = 0.5 |
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super(Triangle, self).__init__(freq, **kwargs) |
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class WhiteNoise(SignalGenerator): |
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def generate(self): |
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while True: |
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yield (random.random() * 2) - 1.0 |
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