max / audiofiles

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1	//! Integrated loudness measurement in LUFS per ITU-R BS.1770-4.
2
3	/// Measure integrated LUFS loudness per ITU-R BS.1770-4.
4	/// Returns -70.0 for silence/near-silence where gating produces no result.
5	pub fn measure_lufs(samples: &[f32], sample_rate: u32) -> f64 {
6	if samples.is_empty() \|\| sample_rate == 0 {
7	return -70.0;
8	}
9	let mut meter = bs1770::ChannelLoudnessMeter::new(sample_rate);
10	meter.push(samples.iter().copied());
11	let windows = meter.into_100ms_windows();
12	let power = bs1770::gated_mean(windows.as_ref());
13	let lkfs = power.loudness_lkfs() as f64;
14	if lkfs.is_nan() \|\| lkfs.is_infinite() {
15	-70.0
16	} else {
17	lkfs
18	}
19	}
20
21	#[cfg(test)]
22	mod tests {
23	use super::*;
24
25	#[test]
26	fn silence_is_very_quiet() {
27	let silence = vec![0.0f32; 48000];
28	let lufs = measure_lufs(&silence, 48000);
29	// Silence should be extremely quiet (negative infinity or very low)
30	assert!(lufs < -60.0, "silence LUFS should be < -60, got {lufs}");
31	}
32
33	#[test]
34	fn loud_sine_is_near_zero() {
35	let samples: Vec<f32> = (0..48000)
36	.map(\|i\| (2.0 * std::f32::consts::PI * 1000.0 * i as f32 / 48000.0).sin())
37	.collect();
38	let lufs = measure_lufs(&samples, 48000);
39	// A 1kHz full-scale sine should be around -3 LUFS
40	assert!(
41	lufs > -10.0 && lufs < 0.0,
42	"full-scale sine LUFS should be near -3, got {lufs}"
43	);
44	}
45	}
46