diff options
| -rw-r--r-- | tools/pdm2pcm.py | 77 |
1 files changed, 45 insertions, 32 deletions
diff --git a/tools/pdm2pcm.py b/tools/pdm2pcm.py index 765c8b6..4dfc5a4 100644 --- a/tools/pdm2pcm.py +++ b/tools/pdm2pcm.py @@ -14,39 +14,50 @@ def load_pdm_file(filename): return pdm_signal -def cic_decimate(input_signal, decimation_factor=64, stages=3, delay=1): - R = decimation_factor - N = stages - M = delay +class CICFilter: + def __init__(self, decimation=64, delay=1, stages=3): + self.R = decimation + self.M = delay + self.N = stages - # Integrator stages - integrators = [0] * N - integrator_outputs = [] + # Integrator and comb delay lines + self.integrators = [0] * self.N + self.comb_buffers = [[0] * self.M for _ in range(self.N)] + self.comb_indices = [0] * self.N - for sample in input_signal: - integrators[0] += sample - for i in range(1, N): - integrators[i] += integrators[i-1] - integrator_outputs.append(integrators[-1]) + self.input_count = 0 - # Decimation - decimated = integrator_outputs[R-1::R] + def process_sample(self, sample): + sample = int(sample) # ensure it's Python int - # Comb stages - combs = [0] * N - comb_outputs = [] - delays = [[0]*M for _ in range(N)] + for i in range(self.N): + self.integrators[i] = int(self.integrators[i] + sample) + sample = self.integrators[i] - for sample in decimated: - diff = sample - for i in range(N): - delayed = delays[i].pop(0) - delays[i].append(diff) - diff = diff - delayed - combs[i] = diff - comb_outputs.append(combs[-1]) + self.input_count += 1 - return comb_outputs + if self.input_count == self.R: + self.input_count = 0 + comb_input = sample + + for i in range(self.N): + idx = self.comb_indices[i] + delayed = self.comb_buffers[i][idx] + self.comb_buffers[i][idx] = comb_input + self.comb_indices[i] = (idx + 1) % self.M + comb_input = int(comb_input - delayed) + + return comb_input + else: + return None + + def process(self, signal): + output = [] + for s in signal: + y = self.process_sample(s) + if y is not None: + output.append(y) + return output def pdm_to_pcm(pdm_signal, decimation_factor=64, filter_type='fir', filter_kwargs={}): @@ -68,11 +79,11 @@ def pdm_to_pcm(pdm_signal, decimation_factor=64, filter_type='fir', filter_kwarg kwargs = {} kwargs.update(defaults) kwargs.update(filter_kwargs) - # Convert 1-bit PDM to +/-1 format - print(pdm_signal) pdm_signal = pdm_signal.astype(int) - #pdm_signal = [2*s - 1 for s in pdm_signal.astype(int)] - pcm_signal = cic_decimate(pdm_signal, decimation_factor=decimation_factor, **kwargs) + cic = CICFilter(decimation=decimation_factor, **kwargs) + # Convert 1-bit PDM to +/-1 format + pdm_signal = [2*s - 1 for s in pdm_signal.astype(int)] + pcm_signal = cic.process(pdm_signal) pcm_signal = numpy.array(pcm_signal, dtype=float) return pcm_signal @@ -109,9 +120,11 @@ def main(): #print(pcm_data.shape) pcm_data -= numpy.mean(pcm_data) # remove DC offset + pcm_data = pcm_data / (numpy.max(numpy.abs(pcm_data)) * 2.0) # normalize scale print(numpy.min(pcm_data), numpy.max(pcm_data), numpy.mean(pcm_data), pcm_data.dtype) - soundfile.write(out_path, pcm_data, samplerate) + + soundfile.write(out_path, pcm_data, samplerate, subtype='PCM_16') print('Wrote', out_path) if __name__ == '__main__': |