Add pre-packaged dependency libraries (ESP32-audioI2S and PNGdec)

libraries/ESP32-audioI2S/examples/biquad/biquad.py

@@ -0,0 +1,44 @@
+import numpy as np
+# import matplotlib
+# matplotlib.use("TkAgg")   # oder "QtAgg", falls Qt installiert ist
+import matplotlib.pyplot as plt
+from scipy.signal import freqz
+
+# =========================
+# PARAMETER
+# =========================
+fs = 44100            # Samplerate
+N  = 8192             # FFT-Auflösung
+
+# Liste von Biquads (Reihenfolge = Signalfluss)
+biquads = [
+([1.026721, -1.919612, 0.901093], [1.0, -1.922258, 0.925168]), # LOWSHELF
+([0.802626,  -1.424665,  0.670208 ], [1.0, -1.424665,  0.472834 ]), # PEAKINGEQ
+([2.092489, -2.262849, 0.808592], [1.0, -0.597000, 0.235232]), # HIGHSHELF
+]
+
+w = np.linspace(0, np.pi, N)
+H = np.ones_like(w, dtype=complex)
+
+for b, a in biquads:
+    _, h = freqz(b, a, worN=w)
+    H *= h
+
+f = w * fs / (2*np.pi)
+mag_db = 20 * np.log10(np.abs(H) + 1e-12)
+
+# =========================
+# PLOT
+# =========================
+plt.figure(figsize=(9,5))
+plt.semilogx(f, mag_db)
+plt.xlim(20, fs/2)
+plt.ylim(-15, 15)
+plt.grid(True, which='both')
+plt.xlabel("Frequency (Hz)")
+plt.ylabel("Amplitude (dB)")
+plt.title("Biquad frequency response")
+plt.tight_layout()
+# plt.show()
+plt.savefig("biquad_response.png", dpi=150)
+print("Plot gespeichert als biquad_response.png")