Struct BandLayout 

pub struct BandLayout {
    pub bands: NonEmptyVec<Band>,
}

A non-empty ordered collection of Bands that together partition the audible spectrum.

Construct using BandLayout::new for custom layouts, or the preset constructors BandLayout::bark and BandLayout::mel for standard perceptual scales (see bands).

Fields

bands: NonEmptyVec<Band>

The ordered list of bands.

Implementations

impl BandLayout

pub fn bark( n_bands: NonZeroUsize, sample_rate_hz: f32, n_bins: NonZeroUsize, ) -> Self

Creates a Bark-scale band layout.

Divides the spectrum from 0 Hz to Nyquist into n_bands bands spaced evenly on the Bark scale. Bark bands closely model the ear’s critical bands and are used by MPEG psychoacoustic models.

n_bins is the number of spectral bins in the caller’s frequency representation (e.g. MdctParams::n_coefficients() for MDCT, or n_fft / 2 + 1 for a real FFT). Bin indices in the returned bands index into that array.

Arguments

• n_bands – Number of bands. 24 covers the full audible range.
• sample_rate_hz – Sample rate of the audio signal in Hz.
• n_bins – Total number of spectral bins.

Returns

A BandLayout with n_bands entries.

Examples

use audio_samples::BandLayout;
use std::num::NonZeroUsize;

let layout = BandLayout::bark(
    NonZeroUsize::new(24).unwrap(),
    44100.0,
    NonZeroUsize::new(1024).unwrap(),
);
assert_eq!(layout.len().get(), 24);
// All bands fit within the bin range.
for band in layout.as_slice().iter() {
    assert!(band.end_bin <= 1024);
    assert!(band.end_bin > band.start_bin);
}

pub fn mel( n_bands: NonZeroUsize, sample_rate_hz: f32, n_bins: NonZeroUsize, ) -> Self

Creates a Mel-scale band layout.

Divides the spectrum from 0 Hz to Nyquist into n_bands bands spaced evenly on the Mel scale. Mel bands are commonly used for speech and music feature extraction.

n_bins is the number of spectral bins in the caller’s frequency representation. Bin indices in the returned bands index into that array.

Arguments

• n_bands – Number of bands. 40–128 is typical for speech / music.
• sample_rate_hz – Sample rate of the audio signal in Hz.
• n_bins – Total number of spectral bins.

Returns

A BandLayout with n_bands entries.

Examples

use audio_samples::BandLayout;
use std::num::NonZeroUsize;

let layout = BandLayout::mel(
    NonZeroUsize::new(40).unwrap(),
    22050.0,
    NonZeroUsize::new(512).unwrap(),
);
assert_eq!(layout.len().get(), 40);

pub fn erb( n_bands: NonZeroUsize, sample_rate_hz: f32, n_bins: NonZeroUsize, ) -> Self

Creates an ERB-scale band layout.

Divides the spectrum from 0 Hz to Nyquist into n_bands bands spaced evenly on the ERB (Equivalent Rectangular Bandwidth) scale of Glasberg & Moore (1990). ERB bands more accurately model auditory filter widths than Bark bands, particularly at low frequencies, and are used in modern perceptual models (Opus, EVS).

n_bins is the number of spectral bins in the caller’s frequency representation. Bin indices in the returned bands index into that array.

Arguments

• n_bands – Number of bands. 32–64 is typical.
• sample_rate_hz – Sample rate of the audio signal in Hz.
• n_bins – Total number of spectral bins.

Returns

A BandLayout with n_bands entries.

Examples

use audio_samples::BandLayout;
use std::num::NonZeroUsize;

let layout = BandLayout::erb(
    NonZeroUsize::new(32).unwrap(),
    44100.0,
    NonZeroUsize::new(1024).unwrap(),
);
assert_eq!(layout.len().get(), 32);
for band in layout.as_slice().iter() {
    assert!(band.end_bin > band.start_bin);
}

impl BandLayout

pub fn new(bands: &NonEmptySlice<Band>) -> Self

Creates a BandLayout from a non-empty slice of bands.

Arguments

• bands – At least one Band. Bands should be ordered by start_bin and cover non-overlapping frequency ranges.

pub fn len(&self) -> NonZeroUsize

Returns the number of bands.

pub fn as_slice(&self) -> &NonEmptySlice<Band>

Returns a view over all bands.

Trait Implementations

impl Clone for BandLayout

fn clone(&self) -> BandLayout

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for BandLayout

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl PartialEq for BandLayout

fn eq(&self, other: &BandLayout) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl StructuralPartialEq for BandLayout