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import numpy as np
import soundfile
def second_order_delta_sigma(pcm):
# Normalize input XXX: remove normalization
#pcm = pcm / np.max(np.abs(pcm))
n = len(pcm)
pdm = np.zeros(n, dtype=np.uint8)
integrator1 = 0.0
integrator2 = 0.0
quantized = 0.0
for i in range(n):
integrator1 += pcm[i] - quantized
integrator2 += integrator1 - quantized
if integrator2 >= 0:
quantized = 1.0
pdm[i] = 1
else:
quantized = -1.0
pdm[i] = 0
return pdm
def save_pdm_bin(pdm_data, file):
packed = np.packbits(pdm_data)
file.write(packed)
def convert(pcm_data, oversample = 64):
# Oversample
pcm_upsampled = np.repeat(pcm_data, oversample)
# --- Convert to PDM ---
pdm_data = second_order_delta_sigma(pcm_upsampled)
return pdm_data
def convert_file(input_file, **kwargs):
# --- Load audio ---
pcm_data, samplerate = soundfile.read(input_file)
# If stereo, use one channel
if pcm_data.ndim > 1:
pcm_data = pcm_data[:, 0]
pdm_data = convert(pcm_data, **kwargs)
return pdm_data
def parse():
import argparse
parser = argparse.ArgumentParser(description='Process an input file and write to an output file.')
parser.add_argument('-i', '--input', type=str, required=True, help='Path to the input file')
parser.add_argument('-o', '--output', type=str, required=True, help='Path to the output file')
args = parser.parse_args()
return args
def main():
args = parse()
out_path = args.output
pdm_data = convert_file(args.input, oversample=64)
with open(out_path, 'wb') as f:
save_pdm_bin(pdm_data, f)
print('Wrote', out_path)
if __name__ == '__main__':
main()
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