oximedia-effects 0.1.1

Professional audio effects suite for OxiMedia
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142

//! Channel vocoder implementation.

use crate::{
    filter::{FilterMode, StateVariableConfig, StateVariableFilter},
    utils::EnvelopeFollower,
    AudioEffect,
};

/// Vocoder configuration.
#[derive(Debug, Clone)]
pub struct VocoderConfig {
    /// Number of frequency bands.
    pub bands: usize,
    /// Attack time in milliseconds.
    pub attack_ms: f32,
    /// Release time in milliseconds.
    pub release_ms: f32,
}

impl Default for VocoderConfig {
    fn default() -> Self {
        Self {
            bands: 16,
            attack_ms: 5.0,
            release_ms: 50.0,
        }
    }
}

/// Vocoder band.
struct VocoderBand {
    modulator_filter: StateVariableFilter,
    carrier_filter: StateVariableFilter,
    envelope: EnvelopeFollower,
}

/// Channel vocoder effect.
///
/// Imposes the spectral characteristics of one signal (modulator)
/// onto another (carrier).
pub struct Vocoder {
    bands: Vec<VocoderBand>,
    #[allow(dead_code)]
    config: VocoderConfig,
}

impl Vocoder {
    /// Create new vocoder.
    #[must_use]
    pub fn new(config: VocoderConfig, sample_rate: f32) -> Self {
        let num_bands = config.bands.clamp(4, 32);

        // Create frequency bands logarithmically spaced
        let min_freq = 100.0_f32;
        let max_freq = 8000.0_f32;

        let bands: Vec<VocoderBand> = (0..num_bands)
            .map(|i| {
                #[allow(clippy::cast_precision_loss)]
                let ratio = i as f32 / (num_bands - 1) as f32;
                let frequency = min_freq * (max_freq / min_freq).powf(ratio);

                let filter_config = StateVariableConfig {
                    frequency,
                    resonance: 2.0,
                    mode: FilterMode::BandPass,
                };

                VocoderBand {
                    modulator_filter: StateVariableFilter::new(filter_config.clone(), sample_rate),
                    carrier_filter: StateVariableFilter::new(filter_config, sample_rate),
                    envelope: EnvelopeFollower::new(
                        config.attack_ms,
                        config.release_ms,
                        sample_rate,
                    ),
                }
            })
            .collect();

        Self { bands, config }
    }

    /// Process modulator and carrier signals.
    pub fn process(&mut self, modulator: f32, carrier: f32) -> f32 {
        let mut output = 0.0;

        #[allow(clippy::cast_precision_loss)]
        let num_bands = self.bands.len() as f32;

        for band in &mut self.bands {
            // Filter modulator and detect envelope
            let mod_filtered = band.modulator_filter.process_sample(modulator);
            let envelope = band.envelope.process(mod_filtered);

            // Filter carrier and apply envelope
            let car_filtered = band.carrier_filter.process_sample(carrier);
            output += car_filtered * envelope;
        }

        output / num_bands
    }
}

impl AudioEffect for Vocoder {
    fn process_sample(&mut self, input: f32) -> f32 {
        // For mono processing, use input as both modulator and carrier
        self.process(input, input)
    }

    fn reset(&mut self) {
        for band in &mut self.bands {
            band.modulator_filter.reset();
            band.carrier_filter.reset();
            band.envelope.reset();
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_vocoder() {
        let config = VocoderConfig::default();
        let mut vocoder = Vocoder::new(config, 48000.0);

        let output = vocoder.process(0.5, 0.3);
        assert!(output.is_finite());
    }

    #[test]
    fn test_vocoder_bands() {
        let config = VocoderConfig {
            bands: 8,
            ..Default::default()
        };
        let vocoder = Vocoder::new(config, 48000.0);
        assert_eq!(vocoder.bands.len(), 8);
    }
}