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# Copyright 2022 Google LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Audio tools."""
import itertools
import math
import os
from threading import Thread
import numpy as np
from scipy.io import wavfile
SINE_FREQUENCY = 440
SINE_DURATION = 0.1
# File which stores the audio signal output data (after transport).
# Used for running comparisons with the generated audio signal.
OUTPUT_WAV_FILE = '/tmp/audiodata'
WAV_RIFF_SIZE_OFFSET = 4
WAV_DATA_SIZE_OFFSET = 40
def _fixup_wav_header(path):
with open(path, 'r+b') as f:
f.seek(0, os.SEEK_END)
file_size = f.tell()
for offset in [WAV_RIFF_SIZE_OFFSET, WAV_DATA_SIZE_OFFSET]:
size = file_size - offset - 4
f.seek(offset)
f.write(size.to_bytes(4, byteorder='little'))
class AudioSignal:
"""Audio signal generator and verifier."""
def __init__(self, transport, amplitude, fs):
"""Init AudioSignal class.
Args:
transport: function to send the generated audio data to.
amplitude: amplitude of the signal to generate.
fs: sampling rate of the signal to generate.
"""
self.transport = transport
self.amplitude = amplitude
self.fs = fs
self.thread = None
def start(self):
"""Generates the audio signal and send it to the transport."""
self.thread = Thread(target=self._run)
self.thread.start()
def _run(self):
sine = self._generate_sine(SINE_FREQUENCY, SINE_DURATION)
# Interleaved audio.
stereo = np.zeros(sine.size * 2, dtype=sine.dtype)
stereo[0::2] = sine
# Send 4 second of audio.
audio = itertools.repeat(stereo.tobytes(), int(4 / SINE_DURATION))
self.transport(audio)
def _generate_sine(self, f, duration):
sine = self.amplitude * \
np.sin(2 * np.pi * np.arange(self.fs * duration) * (f / self.fs))
s16le = (sine * 32767).astype('<i2')
return s16le
def verify(self):
"""Verifies that the audio signal is correctly output."""
assert self.thread is not None
self.thread.join()
self.thread = None
_fixup_wav_header(OUTPUT_WAV_FILE)
samplerate, data = wavfile.read(OUTPUT_WAV_FILE)
# Take one second of audio after the first second.
audio = data[samplerate:samplerate*2, 0].astype(np.float) / 32767
assert len(audio) == samplerate
spectrum = np.abs(np.fft.fft(audio))
frequency = np.fft.fftfreq(samplerate, d=1/samplerate)
amplitudes = spectrum / (samplerate/2)
index = np.where(frequency == SINE_FREQUENCY)
amplitude = amplitudes[index][0]
match_amplitude = math.isclose(
amplitude, self.amplitude, rel_tol=1e-03)
return match_amplitude
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