max / audiofiles

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1	//! Gain adjustment: apply a dB offset with clipping protection.
2
3	/// Apply a gain offset in dB to all samples, clamping to [-1.0, 1.0].
4	pub fn apply_gain(samples: &mut [f32], db: f64) {
5	if samples.is_empty() \|\| db == 0.0 \|\| !db.is_finite() {
6	return;
7	}
8
9	let scale = 10.0_f64.powf(db / 20.0) as f32;
10	for sample in samples.iter_mut() {
11	sample = (sample * scale).clamp(-1.0, 1.0);
12	}
13	}
14
15	#[cfg(test)]
16	mod tests {
17	use super::*;
18
19	#[test]
20	fn gain_plus_6db() {
21	let mut samples = vec![0.25, -0.25, 0.1];
22	apply_gain(&mut samples, 6.0);
23	// +6 dB ≈ 2x
24	let scale = 10.0_f64.powf(6.0 / 20.0) as f32;
25	assert!((samples[0] - 0.25 * scale).abs() < 0.001);
26	assert!((samples[1] - (-0.25 * scale)).abs() < 0.001);
27	}
28
29	#[test]
30	fn gain_minus_6db() {
31	let mut samples = vec![1.0, -1.0, 0.5];
32	apply_gain(&mut samples, -6.0);
33	let scale = 10.0_f64.powf(-6.0 / 20.0) as f32;
34	assert!((samples[0] - scale).abs() < 0.001);
35	}
36
37	#[test]
38	fn gain_zero_is_noop() {
39	let original = vec![0.5, -0.5, 0.25];
40	let mut samples = original.clone();
41	apply_gain(&mut samples, 0.0);
42	assert_eq!(samples, original);
43	}
44
45	#[test]
46	fn gain_clips_to_bounds() {
47	let mut samples = vec![0.5, -0.5];
48	apply_gain(&mut samples, 24.0); // +24 dB ≈ 15.85x, will clip
49	assert_eq!(samples[0], 1.0);
50	assert_eq!(samples[1], -1.0);
51	}
52
53	#[test]
54	fn gain_empty() {
55	let mut samples: Vec<f32> = vec![];
56	apply_gain(&mut samples, 6.0);
57	assert!(samples.is_empty());
58	}
59	}
60