Add license/readme

LICENSE.txt

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2022 Geraint Luff / Signalsmith Audio Ltd.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

@@ -0,0 +1,86 @@
+# Signalsmith Stretch: pitch/time library
+
+This is a C++11 library for pitch and time stretching, using the final approach from the ADC22 presentation _Four Ways To Write A Pitch-Shifter_.
+
+## How to use it
+
+
+```cpp
+#include "signalsmith-stretch.h"
+
+signalsmith::stretch::SignalsmithStretch<float> stretch;
+```
+
+### Configuring
+
+The easiest way to configure is `.presetDefault()`:
+
+```cpp
+stretch.presetDefault(channels, sampleRate);
+```
+
+If you want to test out different block-sizes etc. then you can use `.configure()` manually, and even change `.freqWeight`/`.timeWeight`/`.channelWeight`.
+
+### Processing (and resetting)
+
+```cpp
+// Clears internal buffers
+stretch.reset();
+
+float **inputBuffers, **outputBuffers;
+int inputSamples, outputSamples;
+stretch.process(inputBuffers, inputSamples, outputBuffers, outputSamples);
+
+// Inspect latency
+int totalLatency = stretch.inputLatency() + stretch.outputLatency();
+```
+
+The `.process()` method takes anything where `buffer[channel][index]` gives you a sample.  This could be a `float **` or a `double **` or some custom object.
+
+To get a time-stretch, just hand it differently-sized input/output buffers.
+
+### Pitch-shifting
+
+```cpp
+stretch.setTransposeFactor(2); // up one octave
+
+stretch.setTransposeSemitones(12); // also one octave
+```
+
+You can set a "tonality limit", which uses a non-linear frequency map to preserve a bit more of the timbre:
+
+```cpp
+stretch.setTransposeSemitones(4, 8000/sampleRate);
+```
+
+### Custom pitch map
+
+This stretcher does (fairly rough) peak-detection, and creates a non-linear frequency map based on that.
+
+You can hook into this to define your own pitch-map, by providing a callback which is called once per channel, for every FFT block:
+
+```cpp
+stretch.setMap([&](int channel) {
+	for (auto &peak : stretch.peaks) {
+		peak.output = peak.input*2; // up one octave
+	}
+});
+```
+
+The input/output frequencies are relative to Nyquist.  It's not currently-tested what happens if your map is non-monotonic.
+
+## Compiling
+
+Just include `signalsmith-stretch.h` in your build.
+
+It's pretty slow if optimisation is disabled though, so you might want to enable optimisation just where it's used.
+
+### DSP Library
+
+This uses the Signalsmith DSP library for FFTs and other bits and bobs.
+
+For convenience, a copy of the license is included (with its own `LICENSE.txt`) in `dsp/`, but if you're already using this elsewhere then you should remove this copy to avoid versioning issues.
+
+## License
+
+[MIT License](LICENSE.txt) for now - get in touch if you need anything else.

signalsmith-stretch.h

@@ -19,10 +19,10 @@ struct SignalsmithStretch {
 	int intervalSamples() const {
 		return stft.interval();
 	}
-	int inputLatencySamples() const {
+	int inputLatency() const {
 		return stft.windowSize()/2;
 	}
-	int outputLatencySamples() const {
+	int outputLatency() const {
 		return stft.windowSize() - inputLatencySamples();
 	}