Merge pull request #9 from bmcfee/quality-tests

Resampling quality tests

tests/test_quality.py

@@ -0,0 +1,64 @@
+#!/usr/bin/env python
+
+import numpy as np
+
+import resampy
+
+from nose.tools import raises
+
+def make_tone(freq, sr, duration):
+    return np.sin(2 * np.pi * freq / sr * np.arange(sr * duration))
+
+
+def make_sweep(freq, sr, duration):
+
+    return np.sin(np.cumsum(2 * np.pi * np.logspace(np.log2(2.0 / sr),
+                                                    np.log2(float(freq) / sr),
+                                                    num=duration*sr, base=2.0)))
+
+def test_quality_sine():
+
+    def __test(sr_orig, sr_new, fil, rms, x, y):
+
+        y_pred = resampy.resample(x, sr_orig, sr_new, filter=fil)
+
+        idx = slice(sr_new // 2, - sr_new//2)
+
+        err = np.mean(np.abs(y[idx] - y_pred[idx]))
+        assert err <= rms, '{:g} > {:g}'.format(err, rms)
+
+    FREQ = 512.0
+    DURATION = 2.0
+
+    for (sr_orig, sr_new) in [ (44100, 22050), (22050, 44100) ]:
+        x = make_tone(FREQ, sr_orig, DURATION)
+        y = make_tone(FREQ, sr_new, DURATION)
+
+        for (fil, rms) in [('sinc_window', 1e-6),
+                           ('kaiser_fast', 1e-4),
+                           ('kaiser_best', 1e-7)]:
+            yield __test, sr_orig, sr_new, fil, rms, x, y
+
+def test_quality_sweep():
+
+    def __test(sr_orig, sr_new, fil, rms, x, y):
+
+        y_pred = resampy.resample(x, sr_orig, sr_new, filter=fil)
+
+        idx = slice(sr_new // 2, - sr_new//2)
+
+        err = np.mean(np.abs(y[idx] - y_pred[idx]))
+        assert err <= rms, '{:g} > {:g}'.format(err, rms)
+
+    FREQ = 8192
+    DURATION = 5.0
+
+    for (sr_orig, sr_new) in [ (44100, 22050), (22050, 44100) ]:
+        x = make_sweep(FREQ, sr_orig, DURATION)
+        y = make_sweep(FREQ, sr_new, DURATION)
+
+        for (fil, rms) in [('sinc_window', 1e-1),
+                           ('kaiser_fast', 1e-1),
+                           ('kaiser_best', 1e-1)]:
+            yield __test, sr_orig, sr_new, fil, rms, x, y
+