TrebledJ · April 7, 2023 18:31 · Apr 7, 2023 · Apr 7, 2023 · Apr 7, 2023 · Mar 8, 2023
diff --git a/wavetable_synthesis.py b/wavetable_synthesis.py
@@ -141,6 +141,6 @@ def update(frame):
 ani = FuncAnimation(fig, update, gen, interval=interval)
 
 if save_animation:
-    ani.save('wavetable_synthesis.gif', writer='imagemagick', fps=1000 // interval)
+    ani.save('wavetable-synthesis.gif', writer='imagemagick', fps=1000 // interval)
 else:
     plt.show()
diff --git a/wavetable_synthesis.py b/wavetable_synthesis.py
@@ -0,0 +1,146 @@
+# Wavetable Synthesis Demo
+# by @TrebledJ
+
+from matplotlib.patches import ConnectionPatch
+import matplotlib.ticker as mticker
+import matplotlib.pyplot as plt
+from matplotlib.animation import FuncAnimation
+import numpy as np
+
+
+# Wavetable Parameters
+table_size = 32     # Size of the wavetable (lookup table).
+
+# Generation Parameters
+freq = 8            # Frequency of the sine wave to generate (in Hz).
+sample_rate = 100   # Sampling rate of the generated signal.
+nsamples = 25       # Number of samples to generate.
+
+# Animation Parameters
+# Save the animation (True) or play the animation using Matplotlib's rendering (False).
+save_animation = True
+
+# Number of milliseconds between frames.
+interval = 500
+
+
+def generate_samples(wavetable, freq, sample_rate, *, once=False, nsamples=20):
+    """
+    Generate samples from a wavetable.
+
+    Note that `sample_rate` should be at least `2 * freq`, and the 
+
+    ### Parameters
+    1. wavetable : np.array[float]
+            - The wavetable containing all the pregenerated samples.
+    2. freq : float
+            - The frequency of the waveform to generate.
+    3. sample_rate : float
+            - The sampling rate of the waveform to generate.
+    4. once : bool
+            - True to make at most one pass through the wavetable.
+            - False to run for `nsamples` times.
+    5. nsamples : int
+            - Number of samples to generate.
+    
+    ### Returns
+     - A generator yielding (phases, samples), i.e. (x, y) values along the wavetable.
+    """
+    phases = []  # Stores phases (x).
+    samples = []  # Stores samples (y).
+
+    # The phase is a float with two components: the integer part and the decimal part.
+    # The integer part indicates the sample along the wavetable which we are at, modulus
+    # the wavetable's length. The decimal part indicates the fraction between the left and
+    # right samples.
+    phase = 0
+    for _ in range(nsamples):
+        if once and phase > table_size:
+            break
+
+        idx = int(phase)   # Integer part.
+        frac = phase - idx # Decimal part.
+
+        samp0 = wavetable[idx]
+        samp1 = wavetable[(idx + 1) % table_size]
+        samp = samp0 + (samp1 - samp0) * frac  # Interpolate!
+
+        phases.append(phase)
+        samples.append(samp)
+
+        yield phases, samples
+
+        phase += table_size * freq / sample_rate
+        phase %= table_size
+
+    yield None
+
+
+t = np.linspace(0, 1, table_size + 1)
+wavetable = np.sin(2 * np.pi * t)
+
+
+fig, ax = plt.subplots(2, 1)
+
+ax[0].plot(t * table_size, wavetable, 'bo-')
+ax[0].set_title("Wavetable (Lookup Table)")
+ax[0].axis('off')
+
+ax[1].set_title('Samples')
+ax[1].set_xlim(-0.5, nsamples + 0.5)
+ax[1].set_ylim(-1.1, 1.1)
+ax[1].xaxis.set_major_locator(mticker.MultipleLocator(5))
+
+
+# We'll store drawn points and connections (to be removed on subsequent iterations).
+points = []
+connections = []
+
+
+def update(frame):
+    """
+    Update the animation frame with the next sample.
+    """
+    if frame is None:
+        # Finished!
+        try:
+            points[-1].remove()
+            connections[-1].remove()
+        except:
+            pass
+
+        # Freeze!
+        ani.pause()
+        return fig,
+
+    ph, samples = frame
+
+    wt_x = ph[-1] % table_size
+    wt_y = samples[-1]
+    p = ax[0].plot([wt_x], [wt_y], 'ro', ms=4)
+    ax[1].plot(np.arange(len(samples)), samples, 'ro')
+
+    # Magic line between axs.
+    con = ConnectionPatch(xyA=(wt_x, wt_y), xyB=(len(samples) - 1, samples[-1]), coordsA=ax[0].transData, coordsB=ax[1].transData,
+                          color="red")
+    fig.add_artist(con)
+
+    try:
+        points[-1].remove()
+        connections[-1].remove()
+    except:
+        pass
+
+    points.append(p[0])
+    connections.append(con)
+
+    return fig,
+
+
+gen = generate_samples(wavetable, freq, sample_rate, nsamples=nsamples)
+ani = FuncAnimation(fig, update, gen, interval=interval)
+
+if save_animation:
+    ani.save('wavetable_synthesis.gif', writer='imagemagick', fps=1000 // interval)
+else:
+    plt.show()
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