chore: import upstream snapshot with attribution

utils/pitch_utils.py

@@ -0,0 +1,27 @@
+import numpy as np
+
+
+def norm_f0(f0, uv=None):
+    if uv is None:
+        uv = f0 == 0
+    f0 = np.log2(f0 + uv)  # avoid arithmetic error
+    f0[uv] = -np.inf
+    return f0
+
+
+def interp_f0(f0, uv=None):
+    if uv is None:
+        uv = f0 == 0
+    f0 = norm_f0(f0, uv)
+    if uv.any() and not uv.all():
+        f0[uv] = np.interp(np.where(uv)[0], np.where(~uv)[0], f0[~uv])
+    return denorm_f0(f0, uv=None), uv
+
+
+def denorm_f0(f0, uv, pitch_padding=None):
+    f0 = 2 ** f0
+    if uv is not None:
+        f0[uv > 0] = 0
+    if pitch_padding is not None:
+        f0[pitch_padding] = 0
+    return f0