Crate bs1770

Loudness analysis conforming to ITU-R BS.1770-4.

This library offers the building blocks to perform BS.1770 loudness measurements, but you need to put the pieces together yourself.

Stereo integrated loudness example

let sample_rate_hz = 44_100;
let bits_per_sample = 16;
let channel_samples: [Vec<i16>; 2] = load_stereo_audio();

// When converting integer samples to float, note that the maximum amplitude
// is `1 << (bits_per_sample - 1)`, one bit is the sign bit.
let normalizer = 1.0 / (1_u64 << (bits_per_sample - 1)) as f32;

let channel_power: Vec<_> = channel_samples.iter().map(|samples| {
    let mut meter = bs1770::ChannelLoudnessMeter::new(sample_rate_hz);
    meter.push(samples.iter().map(|&s| s as f32 * normalizer));
    meter.into_100ms_windows()
}).collect();

let stereo_power = bs1770::reduce_stereo(
    channel_power[0].as_ref(),
    channel_power[1].as_ref(),
);

let gated_power = bs1770::gated_mean(stereo_power.as_ref());
println!("Integrated loudness: {:.1} LUFS", gated_power.loudness_lkfs());

Structs

ChannelLoudnessMeter

Measures K-weighted power of non-overlapping 100ms windows of a single channel of audio.

Power

The mean of the squares of the K-weighted samples in a window of time.

Windows100ms

A T value for non-overlapping windows of audio, 100ms in length.

Functions

gated_mean

Perform gating and averaging for a BS.1770-4 integrated loudness measurement.

reduce_stereo

Combine power for multiple channels by taking a weighted sum.

reduce_stereo_in_place

In-place version of reduce_stereo that stores the result in the former left channel.