tools: Fixup PDM reference conversion

Seems to agree pretty well with itself now
PDM bitstream also looks plausible for a sinewave

1 files changed, 91 insertions, 0 deletions

diff --git a/tools/test_pdm.py b/tools/test_pdm.py
new file mode 100644
index 0000000..3bac00b
--- /dev/null
+++ b/tools/test_pdm.py
@@ -0,0 +1,91 @@
+
+import numpy
+import soundfile
+import numpy as np
+import matplotlib.pyplot as plt
+
+from pcm2pdm import convert, convert_file, save_pdm_bin
+from pdm2pcm import pdm_to_pcm, load_pdm_file
+from testsignal import generate_test_tone
+
+def plot_reconstruct(pcm_in, pdm, pcm_reconstructed, sr, aspect = 4.0, height = 3.0):
+    # --- Plotting using OO API ---
+    
+    width = height * aspect
+    figheight = height * 3
+    fig, axs = plt.subplots(3, 1, figsize=(width, figheight), sharex=True)
+
+    duration = pcm_in.shape[0] / sr
+    print(duration)
+    t = np.linspace(0, duration, int(sr * duration), endpoint=False)
+
+    # Plot original PCM
+    axs[0].plot(t, pcm_in, label="PCM_in", color='blue')
+    axs[0].set_title("Original PCM")
+    axs[0].set_ylabel("Amplitude")
+    axs[0].set_ylim(-1.2, 1.2)
+    axs[0].grid(True)
+
+    # Plot PDM bitstream
+    time_pdm = np.linspace(0, duration, len(pdm), endpoint=False)
+    axs[1].step(time_pdm, pdm, where='mid', color='black')
+    axs[1].set_title("PDM Bitstream")
+    axs[1].set_ylabel("Bit")
+    axs[1].set_ylim(-0.2, 1.2)
+    axs[1].grid(True)
+
+    # Plot reconstructed PCM
+    axs[2].plot(t, pcm_reconstructed[:len(t)], label="PCM_rec", color='green')
+    axs[2].set_title("Reconstructed PCM")
+    axs[2].set_ylabel("Amplitude")
+    axs[2].set_xlabel("Time [s]")
+    axs[2].set_ylim(-1.2, 1.2)
+    axs[2].grid(True)
+
+    fig.tight_layout()
+    return fig
+
+def test_sine():
+
+    # temp files
+    pcm_file = 'test.wav'
+    pdm_file = 'test.pdm'
+
+    # Generate test data
+    oversample = 32
+    sample_rate = 16000
+    signal = generate_test_tone(sample_rate=sample_rate,
+        duration_sec=1.000, freqs=[1000.0], noise_level=0.0)
+    pcm = signal
+    soundfile.write(pcm_file, signal, sample_rate)
+
+    # Convert to PDM
+
+    pdm_data = convert_file(pcm_file, oversample=oversample)
+    with open(pdm_file, 'wb') as f:
+        save_pdm_bin(pdm_data, f)
+
+    pdm_loaded = load_pdm_file(pdm_file)
+
+    numpy.testing.assert_equal(pdm_loaded, pdm_data)
+
+    print(pdm_data)
+    print(pdm_loaded)
+
+    # PDM to PCM conversion
+    pcm_reconstructed = pdm_to_pcm(pdm_loaded, decimation_factor=oversample)
+
+    # Remove DC offset
+    pcm_reconstructed -= numpy.mean(pcm_reconstructed)
+
+    fig = plot_reconstruct(pcm, pdm_loaded, pcm_reconstructed, sr=sample_rate)
+    print(fig.axes)
+    offset = 0.2
+    fig.axes[0].set_xlim(offset+0.0010,offset+0.0020)
+
+    plot_path = 'test.png'
+    fig.savefig(plot_path)
+    print(f'Saved {plot_path}')
+
+if __name__ == '__main__':
+    test_sine()