ness_stretch

Algorithm by Alex Ness and Sam Pluta

Rust version by Sam Pluta

Implements a phase randomized Real FFT time stretch algorithm, the NessStretch, which splits the original sound file into 9 discrete frequency bands, and uses a decreasing frame size to correspond to increasing frequency. Starting with a largest frame of 65536, the algorithm will use the following frequency band/frame size breakdown (assuming 44100 Hz input):

0-86 Hz : 65536 frames, 86-172 : 32768, 172-344 : 16384, 344-689 : 8192, 689-1378 : 4096, 1378-2756 : 2048, 2756-5512 : 1024, 5512-11025 : 512, 11025-22050 : 256.

The NessStretch is a refinement of Paul Nasca's excellent PaulStretch algorithm. PaulStretch uses a single frame size throughout the entire frequency range. The NessStretch's layered analysis bands are a better match for human frequency perception, and do a better job of resolving shorter, noisier high-frequency sounds (sibilance, snares, etc.).

See the ICMC paper for more details. Or just run it and give it a listen.

Installation

Rust

For an optimized version of the NessStretch, use the command-line Rust version, which can be installed in a couple of different ways:

1. via homebrew (mac universal build, so it should run on all macs), by running:

brew tap spluta/ness_stretch
brew install ness_stretch

then

ness_stretch -h

for the help.

2. Rust cargo users can install with cargo:

cargo install ness_stretch

Mac x86, Linux and Windows builds (untested auto builds using GitHub actions) are found here:

https://github.com/spluta/ness_stretch/releases/tag/0.2.3

Or download the Rust source and compile using cargo.