main application with tuning, playing, and GUI

fmdemod_old.py

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+import numpy as np
+import scipy.signal
+import wave
+
+def read_raw_iq_samples(file_path):
+    with open(file_path, 'rb') as file:
+        raw_data = file.read()
+    iq_samples = np.frombuffer(raw_data, dtype=np.int8)
+    return iq_samples
+
+def fm_demodulation(iq_samples, sample_rate, fm_deviation=75e3):
+    # Hilbert transform for FM demodulation
+    analytic_signal = scipy.signal.hilbert(iq_samples)
+    instantaneous_phase = np.unwrap(np.angle(analytic_signal))
+    demodulated_signal = np.unwrap(np.angle(iq_samples[1:] * np.conj(iq_samples[:-1]))) / (2.0 * np.pi * 1.0/sample_rate * fm_deviation)
+    return demodulated_signal
+
+def decimate_audio(signal, decimation_factor):
+    return scipy.signal.resample(signal, len(signal)//decimation_factor)
+
+def low_pass_filter(signal, cutoff_frequency, sample_rate):
+    nyquist = 0.5 * sample_rate
+    normal_cutoff = cutoff_frequency / nyquist
+    b, a = scipy.signal.butter(6, normal_cutoff, btype='low', analog=False)
+    filtered_signal = scipy.signal.filtfilt(b, a, signal)
+    return filtered_signal
+
+def save_wav_file(signal, sample_rate, output_file):
+    scaled_signal = np.int16(signal / np.max(np.abs(signal)) * 32767)
+    with wave.open(output_file, 'wb') as wav_file:
+        wav_file.setnchannels(1)
+        wav_file.setsampwidth(2)
+        wav_file.setframerate(sample_rate)
+        wav_file.writeframes(scaled_signal.tobytes())
+
+def main(input_file, output_file, sample_rate, channel_width, decimation_factor=10, cutoff_frequency=75e3):
+    iq_samples = read_raw_iq_samples(input_file)
+    demodulated_signal = fm_demodulation(iq_samples, sample_rate)
+    decimated_signal = decimate_audio(demodulated_signal, decimation_factor)
+    filtered_signal = low_pass_filter(decimated_signal, cutoff_frequency, sample_rate/decimation_factor)
+    new_sample_rate = sample_rate / decimation_factor
+    save_wav_file(filtered_signal, new_sample_rate, output_file)
+
+if __name__ == "__main__":
+    input_file_path = "fm_capture.bin"
+    output_wav_path = "output.wav"
+    sample_rate = 2e6  # Replace with the actual sample rate of your FM stream
+    channel_width = 200e3  # Replace with the channel width of your FM signal
+
+    main(input_file_path, output_wav_path, sample_rate, channel_width)