Add distortion effect. (#2)

* Add distortion effect. * Bump version. * Add tests for distortion. * Reduce memory usage in tests to avoid failures. * Update pedalboard/plugins/Distortion.h Co-authored-by: David Rubinstein <[email protected]> * Update tests/test_native_module.py Co-authored-by: David Rubinstein <[email protected]> * Add more tests for distortion. Co-authored-by: David Rubinstein <[email protected]>
spotify · Aug 2, 2021 · 009d7f3 · 009d7f3
1 parent 8f0fa90
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diff --git a/README.md b/README.md
@@ -18,14 +18,15 @@
    - `Convolution`
    - `Compressor`
    - `Chorus`
+   - `Distortion`
    - `Gain`
    - `HighpassFilter`
-   - `Reverb`
    - `LadderFilter`
    - `Limiter`
    - `LowpassFilter`
    - `Phaser`
- - Supports VST3 plugins on macOS, Windows, and Linux
+   - `Reverb`
+ - Supports VST3® plugins on macOS, Windows, and Linux
  - Supports Audio Units on macOS
  - Strong thread-safety, memory usage, and speed guarantees
    - Releases Python's Global Interpreter Lock (GIL) to allow use of multiple CPU cores
@@ -158,3 +159,5 @@ Contributions to `pedalboard` are welcomed! See [CONTRIBUTING.md](https://github
 
 `pedalboard`'s logo contains artwork called
 ["guitar pedals" by Jino from the Noun Project](https://thenounproject.com/term/guitar-pedals/3605562), and the wordmark uses modified glyphs from [Victor Mono](https://github.com/rubjo/victor-mono).
+
+_VST is a registered trademark of Steinberg Media Technologies GmbH._
diff --git a/pedalboard/plugins/Distortion.h b/pedalboard/plugins/Distortion.h
@@ -0,0 +1,71 @@
+/*
+ * pedalboard
+ * Copyright 2021 Spotify AB
+ *
+ * Licensed under the GNU Public License, Version 3.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    https://www.gnu.org/licenses/gpl-3.0.html
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <pybind11/pybind11.h>
+#include <pybind11/stl.h>
+
+namespace py = pybind11;
+
+#include "../JucePlugin.h"
+
+namespace Pedalboard {
+template <typename SampleType>
+class Distortion
+    : public JucePlugin<juce::dsp::ProcessorChain<
+          juce::dsp::Gain<SampleType>, juce::dsp::WaveShaper<SampleType>>> {
+public:
+  void setDriveDecibels(const float f) noexcept { driveDecibels = f; }
+  float getDriveDecibels() const noexcept { return driveDecibels; }
+
+  virtual void prepare(const juce::dsp::ProcessSpec &spec) override {
+    JucePlugin<juce::dsp::ProcessorChain<juce::dsp::Gain<SampleType>,
+                                         juce::dsp::WaveShaper<SampleType>>>::
+        prepare(spec);
+    this->getDSP().template get<gainIndex>().setGainDecibels(
+        getDriveDecibels());
+    this->getDSP().template get<waveshaperIndex>().functionToUse =
+        [](SampleType x) { return std::tanh(x); };
+  }
+
+private:
+  SampleType driveDecibels;
+
+  enum { gainIndex, waveshaperIndex };
+};
+
+inline void init_distortion(py::module &m) {
+  py::class_<Distortion<float>, Plugin>(
+      m, "Distortion", "Apply soft distortion with a tanh waveshaper.")
+      .def(py::init([](float drive_db) {
+             auto plugin = new Distortion<float>();
+             plugin->setDriveDecibels(drive_db);
+             return plugin;
+           }),
+           py::arg("drive_db") = 25)
+      .def("__repr__",
+           [](const Distortion<float> &plugin) {
+             std::ostringstream ss;
+             ss << "<pedalboard.Distortion";
+             ss << " drive_db=" << plugin.getDriveDecibels();
+             ss << " at " << &plugin;
+             ss << ">";
+             return ss.str();
+           })
+      .def_property("drive_db", &Distortion<float>::getDriveDecibels,
+                    &Distortion<float>::setDriveDecibels);
+}
+}; // namespace Pedalboard
diff --git a/pedalboard/python_bindings.cpp b/pedalboard/python_bindings.cpp
@@ -35,6 +35,7 @@ namespace py = pybind11;
 #include "plugins/Chorus.h"
 #include "plugins/Compressor.h"
 #include "plugins/Convolution.h"
+#include "plugins/Distortion.h"
 #include "plugins/Gain.h"
 #include "plugins/HighpassFilter.h"
 #include "plugins/LadderFilter.h"
@@ -125,6 +126,7 @@ PYBIND11_MODULE(pedalboard_native, m) {
 
   init_compressor(m);
   init_convolution(m);
+  init_distortion(m);
   init_gain(m);
   init_highpass(m);
   init_ladderfilter(m);

diff --git a/setup.py b/setup.py
@@ -200,7 +200,7 @@
 
 setup(
     name='pedalboard',
-    version='0.3.3',
+    version='0.3.4',
     author='Peter Sobot',
     author_email='[email protected]',
     description='A Python library for adding effects to audio.',

diff --git a/tests/test_locking.py b/tests/test_locking.py
@@ -24,7 +24,7 @@
 import pedalboard
 
 
-@pytest.mark.parametrize("num_concurrent_chains", [10, 24, 50])
+@pytest.mark.parametrize("num_concurrent_chains", [2, 10, 20])
 def test_multiple_threads_using_same_plugin_instances(num_concurrent_chains: int):
     """
     Instantiate a large number of stateful plugins, then run audio through them

diff --git a/tests/test_native_module.py b/tests/test_native_module.py
@@ -18,8 +18,8 @@
 import os
 import pytest
 import numpy as np
-from pedalboard import process, Gain, Compressor, Convolution
-
+from pedalboard import process, Distortion, Gain, Compressor, Convolution
+from librosa import db_to_amplitude
 
 IMPULSE_RESPONSE_PATH = os.path.join(os.path.dirname(__file__), "impulse_response.wav")
 
@@ -77,3 +77,16 @@ def test_throw_on_inaccessible_convolution_file():
     # Should fail:
     with pytest.raises(RuntimeError):
         Convolution("missing_impulse_response.wav")
+
+
+@pytest.mark.parametrize("gain_db", [-12, -6, 0, 1.1, 6, 12, 24, 48, 96])
+@pytest.mark.parametrize("shape", [(44100,), (44100, 1), (44100, 2), (1, 4), (2, 4)])
+def test_distortion(gain_db, shape, sr=44100):
+    full_scale_noise = np.random.rand(*shape).astype(np.float32)
+
+    # Use the Distortion transform with ±0dB, which should change nothing:
+    result = process(full_scale_noise, sr, [Distortion(gain_db)])
+
+    np.testing.assert_equal(result.shape, full_scale_noise.shape)
+    gain_scale = db_to_amplitude(gain_db)
+    np.testing.assert_allclose(np.tanh(full_scale_noise * gain_scale), result, rtol=4e-7, atol=2e-7)