Convert PCM wave data to numpy arrays and vice versa

Question

The situation

I am using VAD (Voice Activity Detection) from WebRTC by using WebRTC-VAD, a Python adapter. The example implementation from the GitHub re

Answer 1

It seems that WebRTC-VAD, and the Python wrapper, py-webrtcvad, expects the audio data to be 16bit PCM little-endian - as is the most common storage format in WAV files.

librosa and its underlying I/O library pysoundfile however always returns floating point arrays in the range [-1.0, 1.0]. To convertt this to bytes containing 16bit PCM you can use the following float_to_pcm16 function.

def float_to_pcm16(audio):
    import numpy

    ints = (audio * 32767).astype(numpy.int16)
    little_endian = ints.astype('<u2')
    buf = little_endian.tostring()
    return buf


def read_pcm16(path):
    import soundfile

    audio, sample_rate = soundfile.read(path)
    assert sample_rate in (8000, 16000, 32000, 48000)
    pcm_data = float_to_pcm16(audio)
    return pcm_data, sample_rate