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//! Digital Signal Processing utilities
/// Apply pre-emphasis filter to audio signal
///
/// y[n] = x[n] - coef * x[n-1]
///
/// # Arguments
/// * `signal` - Input audio signal
/// * `coef` - Pre-emphasis coefficient (typically 0.97)
pub fn apply_preemphasis(signal: &[f32], coef: f32) -> Vec<f32> {
if signal.is_empty() {
return vec![];
}
let mut output = Vec::with_capacity(signal.len());
output.push(signal[0]);
for i in 1..signal.len() {
output.push(signal[i] - coef * signal[i - 1]);
}
output
}
/// Apply de-emphasis filter (inverse of pre-emphasis)
///
/// y[n] = x[n] + coef * y[n-1]
pub fn apply_deemphasis(signal: &[f32], coef: f32) -> Vec<f32> {
if signal.is_empty() {
return vec![];
}
let mut output = Vec::with_capacity(signal.len());
output.push(signal[0]);
for i in 1..signal.len() {
output.push(signal[i] + coef * output[i - 1]);
}
output
}
/// Normalize audio to [-1, 1] range
pub fn normalize_audio(signal: &[f32]) -> Vec<f32> {
if signal.is_empty() {
return vec![];
}
let max_abs = signal.iter().map(|x| x.abs()).fold(0.0f32, f32::max);
if max_abs < 1e-8 {
return signal.to_vec();
}
signal.iter().map(|x| x / max_abs).collect()
}
/// Normalize audio to specific peak value
pub fn normalize_audio_peak(signal: &[f32], peak: f32) -> Vec<f32> {
if signal.is_empty() {
return vec![];
}
let max_abs = signal.iter().map(|x| x.abs()).fold(0.0f32, f32::max);
if max_abs < 1e-8 {
return signal.to_vec();
}
let scale = peak / max_abs;
signal.iter().map(|x| x * scale).collect()
}
/// Dynamic range compression (log compression)
///
/// Used for mel spectrogram normalization
pub fn dynamic_range_compression(x: f32) -> f32 {
let clip_val = 1e-5;
(x.max(clip_val)).ln()
}
/// Dynamic range compression for array
pub fn dynamic_range_compression_array(x: &[f32]) -> Vec<f32> {
x.iter().map(|&v| dynamic_range_compression(v)).collect()
}
/// Dynamic range decompression (exp)
pub fn dynamic_range_decompression(x: f32) -> f32 {
x.exp()
}
/// Dynamic range decompression for array
pub fn dynamic_range_decompression_array(x: &[f32]) -> Vec<f32> {
x.iter().map(|&v| dynamic_range_decompression(v)).collect()
}
/// Apply RMS normalization
pub fn normalize_rms(signal: &[f32], target_rms: f32) -> Vec<f32> {
if signal.is_empty() {
return vec![];
}
let rms = (signal.iter().map(|x| x * x).sum::<f32>() / signal.len() as f32).sqrt();
if rms < 1e-8 {
return signal.to_vec();
}
let scale = target_rms / rms;
signal.iter().map(|x| x * scale).collect()
}
/// Apply soft clipping to prevent harsh distortion
pub fn soft_clip(signal: &[f32], threshold: f32) -> Vec<f32> {
signal
.iter()
.map(|&x| {
if x.abs() <= threshold {
x
} else {
let sign = x.signum();
let excess = x.abs() - threshold;
sign * (threshold + (1.0 - (-excess).exp()))
}
})
.collect()
}
/// Pad audio signal with zeros
pub fn pad_audio(signal: &[f32], pad_left: usize, pad_right: usize) -> Vec<f32> {
let mut output = vec![0.0; pad_left];
output.extend_from_slice(signal);
output.extend(vec![0.0; pad_right]);
output
}
/// Trim silence from beginning and end
pub fn trim_silence(signal: &[f32], threshold_db: f32) -> Vec<f32> {
if signal.is_empty() {
return vec![];
}
let threshold = 10f32.powf(threshold_db / 20.0);
// Find first non-silent sample
let start = signal
.iter()
.position(|&x| x.abs() > threshold)
.unwrap_or(0);
// Find last non-silent sample
let end = signal
.iter()
.rposition(|&x| x.abs() > threshold)
.unwrap_or(signal.len() - 1);
if start >= end {
return vec![];
}
signal[start..=end].to_vec()
}
/// Apply fade in/out to avoid clicks
pub fn apply_fade(signal: &[f32], fade_in_samples: usize, fade_out_samples: usize) -> Vec<f32> {
if signal.is_empty() {
return vec![];
}
let mut output = signal.to_vec();
let len = output.len();
// Fade in
for i in 0..fade_in_samples.min(len) {
let factor = i as f32 / fade_in_samples as f32;
output[i] *= factor;
}
// Fade out
for i in 0..fade_out_samples.min(len) {
let idx = len - 1 - i;
let factor = i as f32 / fade_out_samples as f32;
output[idx] *= factor;
}
output
}
/// Compute RMS energy
pub fn compute_rms(signal: &[f32]) -> f32 {
if signal.is_empty() {
return 0.0;
}
(signal.iter().map(|x| x * x).sum::<f32>() / signal.len() as f32).sqrt()
}
/// Compute peak amplitude
pub fn compute_peak(signal: &[f32]) -> f32 {
signal.iter().map(|x| x.abs()).fold(0.0f32, f32::max)
}
/// Compute crest factor (peak/RMS ratio)
pub fn compute_crest_factor(signal: &[f32]) -> f32 {
let rms = compute_rms(signal);
if rms < 1e-8 {
return 0.0;
}
compute_peak(signal) / rms
}
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