simple_src

A simple sample rate conversion lib for audio.

Usage

Usually use sinc Converter, it is flexible and high-quality. The linear Converter is not recommended unless performance is really important and quality is not cared.

sinc

With new method:

use simple_src::{sinc, Convert};

let samples = vec![1.0, 2.0, 3.0, 4.0];
let manager = sinc::Manager::new(2.0, 48.0, 8, 0.1).unwrap();
let mut converter = manager.converter();
for s in converter.process(samples.into_iter()) {
    println!("{s}");
}

Or use builder:

use simple_src::{sinc, Convert};

let samples = vec![1.0, 2.0, 3.0, 4.0];
let manager = sinc::Manager::builder()
    .ratio(2.0)
    .attenuation(48.0)
    .quantify(8)
    .pass_width(0.9)
    .build()
    .unwrap();
let mut converter = manager.converter();
for s in converter.process(samples.into_iter()) {
    println!("{s}");
}

For multi-channel example see two_channels.rs.

linear

use simple_src::{linear, Convert};

let samples = vec![1.0, 2.0, 3.0, 4.0];
let manager = linear::Manager::new(2.0).unwrap();
let mut converter = manager.converter();
for s in converter.process(samples.into_iter()) {
    println!("{s}");
}

Sinc parameters

Recommended initialization parameters for sinc converter:

The relationship between attenuation and quantify is about Q = 2 ^ (A / 12 - 1), A = 12 + 12 * log2(Q).

Due to the amount of calculation and the size of LUT, A = 144 or 156 for 24bit audio is usually fine, and for 16bit, A = 120 is enough.

Plots

Use plots.py to show the results of conversion. It needs numpy, scipy and matplotlib.

Here is an example showing the results of a downsampling 96kHz:

$ cargo test -r --test testwav -- --ignored --exact --show-output generate
$ cargo test -r --test sinc -- --ignored --exact --show-output ta120_2_96k_down
$ python
>>> import plots
>>> import os
>>> os.chdir('output')
>>> plots.spectrum('beep_96k_44k_s_a120_2.wav')
>>> plots.spectrogram('sweep_96k_44k_s_a120_2.wav')
>>> plots.impulse('impulse_96k_44k_s_a120_2.wav')
>>> plots.impulse('impulse_96k_44k_s_a120_2.wav', True)

See code in tests for more details.

References

1. Smith, J.O. Digital Audio Resampling Home Page https://ccrma.stanford.edu/~jos/resample/.
2. Alan V. Oppenheim, Ronald W. Schafer. Discrete-Time Signal Processing, Third Edition.