51e893590c
Rust workspace with 7 crates implementing a custom VoIP protocol designed for extremely lossy connections (5-70% loss, 100-500kbps, 300-800ms RTT). 89 tests passing across all crates. Crates: - wzp-proto: Wire format, traits, adaptive quality controller, jitter buffer, session FSM - wzp-codec: Opus encoder/decoder (audiopus), Codec2 stubs, adaptive switching, resampling - wzp-fec: RaptorQ fountain codes, interleaving, block management (proven 30-70% loss recovery) - wzp-crypto: X25519+ChaCha20-Poly1305, Warzone identity compatible, anti-replay, rekeying - wzp-transport: QUIC via quinn with DATAGRAM frames, path monitoring, signaling streams - wzp-relay: Integration stub (Phase 2) - wzp-client: Integration stub (Phase 2) Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
83 lines
2.4 KiB
Rust
83 lines
2.4 KiB
Rust
//! Simple linear resampler for 48 kHz <-> 8 kHz conversion.
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//!
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//! These are basic implementations suitable for voice. For higher quality,
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//! replace with the `rubato` crate later.
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/// Downsample from 48 kHz to 8 kHz (6:1 decimation with averaging).
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///
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/// Each output sample is the average of 6 consecutive input samples,
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/// providing basic anti-aliasing via a box filter.
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pub fn resample_48k_to_8k(input: &[i16]) -> Vec<i16> {
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const RATIO: usize = 6;
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let out_len = input.len() / RATIO;
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let mut output = Vec::with_capacity(out_len);
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for chunk in input.chunks_exact(RATIO) {
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let sum: i32 = chunk.iter().map(|&s| s as i32).sum();
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output.push((sum / RATIO as i32) as i16);
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}
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output
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}
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/// Upsample from 8 kHz to 48 kHz (1:6 interpolation with linear interp).
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///
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/// Linearly interpolates between each pair of input samples to produce
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/// 6 output samples per input sample.
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pub fn resample_8k_to_48k(input: &[i16]) -> Vec<i16> {
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const RATIO: usize = 6;
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if input.is_empty() {
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return Vec::new();
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}
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let out_len = input.len() * RATIO;
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let mut output = Vec::with_capacity(out_len);
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for i in 0..input.len() {
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let current = input[i] as i32;
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let next = if i + 1 < input.len() {
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input[i + 1] as i32
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} else {
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current // hold last sample
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};
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for j in 0..RATIO {
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let interp = current + (next - current) * j as i32 / RATIO as i32;
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output.push(interp as i16);
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}
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}
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output
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn roundtrip_length() {
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// 960 samples at 48kHz (20ms) -> 160 samples at 8kHz -> 960 samples at 48kHz
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let input_48k = vec![0i16; 960];
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let down = resample_48k_to_8k(&input_48k);
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assert_eq!(down.len(), 160);
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let up = resample_8k_to_48k(&down);
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assert_eq!(up.len(), 960);
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}
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#[test]
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fn dc_signal_preserved() {
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// A constant signal should survive resampling
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let input = vec![1000i16; 960];
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let down = resample_48k_to_8k(&input);
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assert!(down.iter().all(|&s| s == 1000));
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let up = resample_8k_to_48k(&down);
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assert!(up.iter().all(|&s| s == 1000));
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}
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#[test]
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fn empty_input() {
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assert!(resample_48k_to_8k(&[]).is_empty());
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assert!(resample_8k_to_48k(&[]).is_empty());
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}
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}
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