lc3-codec 0.2.0

An implementation of the LC3 audio codec for embedded systems (no_std)
Documentation 
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use crate::common::{complex::Scaler, config::FrameDuration};

// checked against spec

pub struct NoiseLevelEstimation {
    frame_duration: FrameDuration,
    ne: usize,
}

#[allow(unused_imports)]
use num_traits::real::Real;

impl NoiseLevelEstimation {
    pub fn new(frame_duration: FrameDuration, ne: usize) -> Self {
        Self { frame_duration, ne }
    }

    /// Returns an integer between 0 and 7 indicating the noise level
    /// x_f - TNS
    /// x_q - spectral quant
    pub fn calc_noise_factor(&self, x_f: &[Scaler], x_q: &[i16], bandwidth_ind: usize, global_gain: Scaler) -> usize {
        const BW_STOP_TABLE_10MS: [usize; 5] = [80, 160, 240, 320, 400];
        const BW_STOP_TABLE_7P5MS: [usize; 5] = [60, 120, 180, 240, 300];
        let (bw_stop, nf_start, nf_width) = match self.frame_duration {
            FrameDuration::TenMs => (BW_STOP_TABLE_10MS[bandwidth_ind], 24, 3),
            FrameDuration::SevenPointFiveMs => (BW_STOP_TABLE_7P5MS[bandwidth_ind], 18, 2),
        };

        let mut sum = 0.0;
        let mut count = 0;

        let nf_stop = self.ne.min(bw_stop);
        for (k, sample) in x_f.iter().enumerate().take(nf_stop).skip(nf_start) {
            // sample is relevant if all the spectral coefficients in the band
            // have been quantized to zero
            let from = k - nf_width;
            let to = bw_stop.min(k + nf_width + 1);
            let is_relevant = x_q[from..to].iter().all(|x| *x == 0);

            if is_relevant {
                sum += (*sample).abs() / global_gain;
                count += 1;
            }
        }

        let noise_level = if count > 0 { sum / count as Scaler } else { 0.0 };

        // quantize the noise level into eight steps to turn it into a noise factor
        let diff = 8.0 - 16.0 * noise_level;
        if diff >= 0.0 {
            7.min((diff + 0.5) as i32) as usize
        } else {
            0
        }
    }
}

#[cfg(test)]
mod tests {
    extern crate std;
    use super::*;
    use crate::common::config::{FrameDuration, Lc3Config, SamplingFrequency};

    #[test]
    fn noise_level_estimation_run() {
        let config = Lc3Config::new(SamplingFrequency::Hz48000, FrameDuration::TenMs);
        let estimator = NoiseLevelEstimation::new(config.n_ms, config.ne);
        #[rustfmt::skip]
        let x_f = [
            2511.287, -3606.8093, -453.28122, -360.71924, -2574.9756, -3166.2068, 6525.6, 6284.0137, -10303.951,
            -4442.8755, 2318.4038, -691.36865, 509.12134, -938.29266, 525.9005, -1542.4482, -3091.5273, 262.27206,
            -379.65656, -98.486786, 668.16437, -213.70082, -114.14174, 80.94827, 83.418945, -16.794994, 6.197174,
            -332.66284, -48.91777, 0.084522665, -281.5821, 78.69863, 133.78897, 102.63185, -259.9021, -450.69684,
            -538.17615, 102.73462, 256.75674, -122.24531, 414.3129, 90.33753, -141.62321, 64.58323, 158.11197,
            264.04486, -70.996445, -74.847595, 715.87695, 398.03842, -383.14874, 81.798744, 100.61626, 183.76709,
            107.91918, -74.72749, 137.34314, -12.11866, 145.58879, -8.319928, -146.90816, 21.44834, -14.692991,
            -26.504921, -44.41256, 169.60251, 157.3852, 57.295708, -223.72159, -105.66721, 85.917145, -124.74416,
            67.12806, 148.09708, 108.51118, -38.312347, 85.37175, 124.25812, -19.708088, -252.26158, -396.83145,
            30.49828, 24.158318, 4.4514937, -100.692856, -19.743237, 174.73466, -129.2712, -94.76638, -48.278133,
            -12.916355, -108.09598, 15.809202, 102.17793, -36.756264, -59.4923, -168.1815, 18.80262, -43.62355,
            23.15091, 16.152151, -187.13437, 30.643784, 90.79638, -16.21843, -39.05421, 62.11714, -2.155285, -19.06319,
            -42.414265, 35.171066, 84.379585, -116.602325, -33.51855, -7.659307, 44.801598, -11.07798, -14.886959,
            62.95822, 14.218942, 31.104227, -83.76815, 17.044928, 55.428146, -13.889921, -126.15556, -27.248165,
            120.640366, -19.761774, 14.046745, -73.71858, 0.10803318, 10.083524, -16.70562, 4.7014112, -62.691025,
            50.462833, -84.346176, -13.629369, 36.10631, -46.619267, -21.598942, -48.490704, -6.3323555, 15.65649,
            48.896317, -56.442543, -6.640568, -17.761715, -70.73248, -40.4366, -36.27153, 74.86966, -46.19746,
            -44.013317, 2.0889094, 26.809942, -6.282827, -65.310585, 33.484646, -9.667151, 15.079562, -16.305983,
            9.046168, 29.939863, 5.129214, 16.5475, -50.21096, 31.017387, 38.323303, -3.0681198, -36.80033, -1.2009478,
            11.490404, 26.555166, 44.298775, -31.610435, 4.04779, -32.927948, 29.660675, 11.896004, -18.109625,
            25.200207, -23.730797, 15.500507, -25.358208, 6.163124, -7.3798866, -7.921206, -16.156162, -36.149162,
            -1.5045524, -43.494595, 29.947332, -15.511134, -17.982704, -28.039505, -30.445019, -3.5225277, -46.805386,
            -1.0227482, -23.363768, -17.676548, -3.6520846, -12.88875, 4.756609, 31.271141, -6.629322, -37.832882,
            -0.21950912, 38.885174, 21.138603, 6.2617035, -9.60021, -11.284341, -19.242826, -1.6980145, -9.359415,
            -41.126484, -29.448069, -5.9372683, 25.94433, 1.3254867, -14.705631, 15.379487, 16.574158, -27.095804,
            -19.93113, 20.497425, 0.79107094, -7.7554317, -36.76988, -52.092567, -38.030884, -20.167278, -0.28380156,
            -7.2491307, 8.2373905, 7.9681587, 12.655432, 23.266579, 13.15513, 5.5212536, 12.821712, 10.402097, -1.8669,
            17.029139, 7.877034, -3.6022367, -13.437171, -10.018736, 6.7936516, 12.0322485, 17.809977, -13.797862,
            -19.886257, -20.896944, -13.391824, -3.7870193, -6.042081, 9.495218, -8.35246, -16.302475, -16.089418,
            -2.2239032, 5.133191, -1.9499176, -12.571083, -26.08479, -8.472019, -4.010655, 5.987412, -1.6527638,
            -5.525652, -1.8339038, -6.3098893, -2.546278, -14.999996, -4.8673024, -21.751396, -23.044847, 0.98999345,
            3.2206738, 1.6813838, -5.9552116, -2.9898171, -6.6439576, 10.739187, -0.41604716, -6.192164, 10.029629,
            -8.77803, -3.0170813, -3.2569091, -16.77877, -12.368547, 2.8054588, -1.341449, 4.0487995, 9.832774,
            9.444449, 19.458578, -5.653375, -5.7151184, -1.1136432, 2.3793151, 5.6741295, -4.6841993, -0.53913784,
            -5.0413313, -4.085096, -17.153347, -1.8630176, 11.785563, 1.1223254, -0.71278524, -4.503395, 1.1829545,
            -10.829809, -1.1153163, 3.7169714, -0.4367964, -0.591923, -2.8435392, 1.75674, -4.178983, 4.8031635,
            -5.574907, -0.26360065, -4.317787, -11.108944, 12.20769, 3.0794377, -0.6653844, -2.5413795, -2.403656,
            -0.8925853, 13.288289, 6.883606, -15.778875, -1.6005001, 5.696593, 8.6179, -7.1294184, -5.413874,
            5.2202096, 2.9486847, -2.3101602, -2.2582812, 15.61281, -0.8072282, -0.08025418, -4.076133, -9.068343,
            4.1847715, -2.2272792, -1.0373013, -4.7336984, 1.2461259, -0.5397187, 0.18704754, -0.1272373, 0.41515422,
            4.11998, -5.550728, 0.5320622, 3.4917614, 8.215734, -10.053921, -7.784162, 3.4075887, -8.748142,
            0.87312615, -1.6497533, 1.9920977, -0.20973617, -1.9895163, -3.3932712, 1.6009337, 7.0630236, -3.209106,
            5.2722173, -5.2088814, -1.2551317, 2.55086, -3.7561512, -1.9274446, -2.2996173, 5.709345, -2.3815656,
            -0.94840765, 0.60572165, 4.09223, -2.2723556, -4.731332, 2.7107785, -2.495332, 3.3961606, -2.640641,
            -1.3273795,
        ];
        let x_q = [
            102, -146, -18, -14, -104, -128, 264, 254, -417, -180, 94, -28, 20, -38, 21, -62, -125, 10, -15, -4, 27,
            -9, -4, 3, 3, -1, 0, -13, -2, 0, -11, 3, 5, 4, -10, -18, -22, 4, 10, -5, 17, 4, -6, 2, 6, 11, -3, -3, 29,
            16, -15, 3, 4, 7, 4, -3, 5, 0, 6, 0, -6, 1, 0, -1, -2, 7, 6, 2, -9, -4, 3, -5, 3, 6, 4, -1, 3, 5, -1, -10,
            -16, 1, 1, 0, -4, -1, 7, -5, -4, -2, 0, -4, 1, 4, -1, -2, -7, 1, -2, 1, 1, -7, 1, 4, -1, -1, 2, 0, -1, -2,
            1, 3, -5, -1, 0, 2, 0, 0, 2, 0, 1, -3, 1, 2, 0, -5, -1, 5, -1, 0, -3, 0, 0, -1, 0, -2, 2, -3, 0, 1, -2, -1,
            -2, 0, 1, 2, -2, 0, -1, -3, -2, -1, 3, -2, -2, 0, 1, 0, -3, 1, 0, 0, -1, 0, 1, 0, 1, -2, 1, 1, 0, -1, 0, 0,
            1, 2, -1, 0, -1, 1, 0, -1, 1, -1, 1, -1, 0, 0, 0, -1, -1, 0, -2, 1, -1, -1, -1, -1, 0, -2, 0, -1, -1, 0, 0,
            0, 1, 0, -1, 0, 1, 1, 0, 0, 0, -1, 0, 0, -2, -1, 0, 1, 0, 0, 0, 1, -1, -1, 1, 0, 0, -1, -2, -1, -1, 0, 0,
            0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, -1, -1, 0, 0, 0, 0, 0, -1, -1, 0, 0, 0, 0, -1, 0, 0,
            0, 0, 0, 0, 0, 0, 0, 0, -1, -1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, -1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0,
            0, 0, 0, 0, 0, -1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, -1, 0,
            0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        ];
        let p_bw = 4;
        let gg = 24.709114;

        let noise_factor = estimator.calc_noise_factor(&x_f, &x_q, p_bw, gg);

        assert_eq!(noise_factor, 6);
    }
}