A tiny & portable C11 implementation of the Paulstretch extreme audio stretching algorithm.
Paulstretch is originally a GUI program developed by Nasca Octavian Paul. This library was rewritten from scratch to offer the same audio stretching capabilities, in a lightweight C library.
Depends on FFTW3.
meson build/
ninja -C build/
See include/paulstretch.h and example/simple.c for an example.
The general idea is:
double stretch_factor = 10.0;
double buffer_duration = 0.25;
size_t window_size = buffer_duration * 44100;
paulstretch ps = paulstretch_create(stretch_factor, window_size);
float *in = malloc(window_size * sizeof(float));
while(true) {
// read <window_size> float audio samples into in ...
paulstretch_write(ps, in);
float *out;
while(paulstretch_read(ps, &out)) {
// use the <window_size> stretched audio samples from out ...
}
}
free(in);
paulstretch_destroy(ps);The original Paulstretch GUI program has several additional features: onset detection, custom harmonics, pitch shift, frequency shift, octave mixer, ...
This library focuses on the core of the algorithm: sound stretching, without onset detection, much like the Paulstretch plugin for Audacity.
MIT