maudio-router/src/audio/resampling.rs

use rubato::{Resampler, SincFixedIn, SincInterpolationParameters, SincInterpolationType, WindowFunction};

const MAX_CHUNK_SIZE: usize = 1024;

pub fn resampling(
    current_sample_rate: u32,
    target_sample_rate: u32,
    data: Vec<Vec<f32>>,
) -> Result<Vec<Vec<f32>>, Box<dyn std::error::Error>> {
    let channels = data.len();
    let samples = data[0].len();

    let resample_ratio = target_sample_rate as f64 / current_sample_rate as f64;

    let params = SincInterpolationParameters {
        sinc_len: 256,
        f_cutoff: 0.95,
        interpolation: SincInterpolationType::Linear,
        oversampling_factor: 256,
        window: WindowFunction::BlackmanHarris2,
    };

    let mut output = vec![Vec::new(); channels];
    let expected_output_len = (samples as f64 * resample_ratio).round() as usize;

    for chunk_start in (0..samples).step_by(MAX_CHUNK_SIZE) {
        let chunk_end = (chunk_start + MAX_CHUNK_SIZE).min(samples);
        let chunk_size = chunk_end - chunk_start;

        let mut resampler = SincFixedIn::<f32>::new(
            resample_ratio,
            2.0,
            SincInterpolationParameters {
                sinc_len: 256,
                f_cutoff: 0.95,
                interpolation: SincInterpolationType::Linear,
                oversampling_factor: 256,
                window: WindowFunction::BlackmanHarris2,
            },
            chunk_size,
            channels,
        )?;

        let mut input: Vec<&[f32]> = data
            .iter()
            .map(|channel| &channel[chunk_start..chunk_end])
            .collect();

        let mut chunk_output = vec![vec![0.0; resampler.output_frames_next()]; channels];
        let mut output_buffers: Vec<&mut [f32]> = chunk_output
            .iter_mut()
            .map(|channel| channel.as_mut_slice())
            .collect();

        let (_, output_frames) = resampler.process_into_buffer(&input, &mut output_buffers, None)?;

        for (channel_output, chunk_channel_output) in output.iter_mut().zip(chunk_output.iter()) {
            channel_output.extend_from_slice(&chunk_channel_output[..output_frames]);
        }
    }

    for channel in output.iter_mut() {
        channel.truncate(expected_output_len);
    }

    Ok(output)
}