Avoid a time stretch in Rubberband. (#342)

pedalboard/TimeStretch.h

@@ -23,6 +23,7 @@ using namespace RubberBand;
 namespace Pedalboard {
 
 static const int MAX_SEMITONES_TO_PITCH_SHIFT = 72;
+static const size_t STUDY_BLOCK_SAMPLE_SIZE = 2048;
 
 /*
  * A wrapper around Rubber Band that allows calling it independently of a plugin
@@ -105,8 +106,18 @@ timeStretch(const juce::AudioBuffer<float> input, double sampleRate,
   rubberBandStretcher.setMaxProcessSize(input.getNumSamples());
   rubberBandStretcher.setExpectedInputDuration(input.getNumSamples());
 
-  rubberBandStretcher.study(input.getArrayOfReadPointers(),
-                            input.getNumSamples(), true);
+  const float **inputChannelPointers =
+      (const float **)alloca(sizeof(float *) * input.getNumChannels());
+
+  for (size_t i = 0; i < input.getNumSamples(); i += STUDY_BLOCK_SAMPLE_SIZE) {
+    size_t numSamples =
+        std::min(input.getNumSamples() - i, (size_t)STUDY_BLOCK_SAMPLE_SIZE);
+    for (int c = 0; c < input.getNumChannels(); c++) {
+      inputChannelPointers[c] = input.getReadPointer(c, i);
+    }
+    bool isLast = i + numSamples >= input.getNumSamples();
+    rubberBandStretcher.study(inputChannelPointers, numSamples, isLast);
+  }
 
   size_t expectedNumberOfOutputSamples =
       (((double)input.getNumSamples()) / stretchFactor);
@@ -120,8 +131,6 @@ timeStretch(const juce::AudioBuffer<float> input, double sampleRate,
                  /* avoidReallocating */ true);
 
   size_t blockSize = rubberBandStretcher.getProcessSizeLimit();
-  const float **inputChannelPointers =
-      (const float **)alloca(sizeof(float *) * input.getNumChannels());
   float **outputChannelPointers =
       (float **)alloca(sizeof(float *) * output.getNumChannels());
 

tests/test_time_stretch.py

@@ -15,8 +15,9 @@
 # limitations under the License.
 
 
-import pytest
 import numpy as np
+import pytest
+
 from pedalboard import time_stretch
 
 
@@ -104,3 +105,10 @@ def test_time_stretch_long_passthrough(
         high_quality=high_quality,
     )
     np.testing.assert_allclose(output[0], sine_wave, atol=0.25)
+
+
+def test_time_stretch_does_not_segfault():
+    # https://github.com/spotify/pedalboard/issues/340
+    sr = 44100
+    x = np.random.default_rng().uniform(size=sr * 10).astype(np.float32)
+    time_stretch(x, sr, high_quality=False, use_time_domain_smoothing=True)