Merge 737afaa into 0ebe464

pyrubberband/pyrb.py

@@ -18,7 +18,7 @@
 import soundfile as sf
 
 
-__all__ = ['time_stretch', 'pitch_shift']
+__all__ = ['time_stretch', 'pitch_shift', 'timemap_stretch']
 
 __RUBBERBAND_UTIL = 'rubberband'
 
@@ -141,6 +141,66 @@ def time_stretch(y, sr, rate, rbargs=None):
     return __rubberband(y, sr, **rbargs)
 
 
+def timemap_stretch(y, sr, time_map, rbargs=None):
+    '''Apply a timemap stretch to an audio time series.
+
+    This uses the `time` and `timemap` form for rubberband.
+
+
+    Parameters
+    ----------
+    y : np.ndarray [shape=(n,) or (n, c)]
+        Audio time series, either single or multichannel
+
+    sr : int > 0
+        Sampling rate of `y`
+
+    time_map : list
+        Each element is a tuple `t` of length 2 which correspond to the input
+         frame and desired output frame.
+        If t[1] < t[0] the track will be sped up in this area.
+        time_map[-1] must correspond to the lengths of the input audio and
+         output audio.
+
+    rbargs
+        Additional keyword parameters for rubberband
+
+        See `rubberband -h` for details.
+
+    Returns
+    -------
+    y_stretch : np.ndarray
+        Time-stretched audio
+
+    Raises
+    ------
+    ValueError
+        if `rate <= 0`
+    '''
+
+    if rbargs is None:
+        rbargs = dict()
+
+    time_stretch = time_map[-1][1]/time_map[-1][0]
+
+    rbargs.setdefault('--time', time_stretch)
+
+    fs, stretch_file_name = tempfile.mkstemp(suffix='.txt')
+    os.close(fs)
+
+    stretch_file = open(stretch_file_name, 'w')
+    for t in time_map:
+        stretch_file.write("%d %d\n" % (t[0], t[1]))
+    stretch_file.close()
+
+    rbargs.setdefault('--timemap', stretch_file_name)
+
+    y_stretch = __rubberband(y, sr, **rbargs)
+    os.unlink(stretch_file_name)
+
+    return y_stretch
+
+
 def pitch_shift(y, sr, n_steps, rbargs=None):
     '''Apply a pitch shift to an audio time series.
 

tests/test_pyrb.py

@@ -44,6 +44,14 @@ def channels(request):
     return request.param
 
 
+@pytest.fixture
+def time_map(num_samples, request):
+    return [(0, 0),
+            (num_samples//4, num_samples//4),
+            ((3*num_samples)//4, num_samples//2),
+            (num_samples, (3*num_samples)//4)]
+
+
 @pytest.fixture
 def random_signal(channels, num_samples):
     if channels is not None:
@@ -107,6 +115,26 @@ def test_pitch(sr, num_samples, freq, n_step):
     assert np.allclose(s_s / s_s[0], s_f / s_f[0], atol=1e-2)
 
 
+def test_timemap_stretch(sr, num_samples, freq, time_map):
+
+    y = np.cos(2 * np.pi * freq * np.arange(num_samples)/sr)
+    # Apply time strech
+    y_s = pyrubberband.timemap_stretch(y, sr, time_map)
+
+    assert len(y) * time_map[-1][1] == len(y_s) * time_map[-1][0]
+
+    # Make sure the stretched audio signal has the same note as the original
+    fft = np.abs(np.fft.fft(y))
+    fft = fft[:len(fft)//2]
+
+    fft_s = np.abs(np.fft.fft(y_s))
+    fft_s = fft_s[:len(fft_s)//2]
+
+    assert np.isclose(np.argmax(fft) / len(fft),
+                      np.argmax(fft_s) / len(fft_s),
+                      rtol=1e-1)
+
+
 @pytest.mark.parametrize(
     "cli",
     [pytest.mark.xfail('rubberband-missing', raises=RuntimeError),