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);
}

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

Creates a CELT-scale band layout using the RFC 6716 band edges.

Divides the spectrum into up to 21 perceptual bands whose boundaries follow the CELT specification (RFC 6716 §4.3.1, Table 2). Bands that fall entirely above the Nyquist frequency of sample_rate_hz are omitted, so the returned layout may have fewer than 21 entries.

Arguments

• sample_rate_hz – Sample rate of the signal in Hz.
• n_bins – Number of spectral bins (half the FFT size).

Returns

A BandLayout with up to 21 entries.

Examples

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

// 20 ms frame at 44.1 kHz → 882 samples → 441 bins
let layout = BandLayout::celt(44100.0, NonZeroUsize::new(441).unwrap());
assert!(layout.len().get() <= 21);
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