opus-rs

A pure-Rust implementation of the Opus audio codec (RFC 6716), ported from the reference C implementation (libopus 1.6).

Status: Production-ready — SILK-only, CELT-only, and Hybrid modes are functional. Stereo encoding (SILK and CELT) is supported.

Features

• Pure Rust — no C dependencies, no unsafe code in the codec core
• SILK encoder & decoder — narrowband (8 kHz), mediumband (12 kHz), wideband (16 kHz)
• CELT encoder & decoder — fullband (48 kHz) with MDCT, PVQ, energy quantization
• Hybrid mode — SILK for low frequencies + CELT for high frequencies
• Range coder — entropy coding with ICDF tables and Laplace distribution
• VAD — voice activity detection
• HP filter — variable-cutoff high-pass filter for VOIP mode
• CBR / VBR — both constant and variable bitrate modes
• LBRR — in-band forward error correction
• Resampler — high-quality resampling (up2, up2_hq)
• Stereo — mid-side encoding for both SILK and CELT

Quick Start

use opus_rs::{OpusEncoder, OpusDecoder, Application};

// Encode
let mut encoder = OpusEncoder::new(16000, 1, Application::Voip).unwrap();
encoder.bitrate_bps = 16000;
encoder.use_cbr = true;

let input = vec![0.0f32; 320]; // 20ms frame at 16kHz
let mut output = vec![0u8; 256];
let bytes = encoder.encode(&input, 320, &mut output).unwrap();

// Decode
let mut decoder = OpusDecoder::new(16000, 1).unwrap();
let mut pcm = vec![0.0f32; 320];
let samples = decoder.decode(&output[..bytes], 320, &mut pcm).unwrap();

Testing

cargo test

All 156 tests pass, covering MDCT identity, PVQ consistency, SILK/CELT/Hybrid encode/decode roundtrip, resampler tests, and more.

WAV Roundtrip

# Rust encoder/decoder
cargo run --example wav_test

# Compare with C libopus (requires opusic-sys)
cargo run --example wav_test_c

Stereo Tests

cargo run --example stereo_test

Performance

Run benchmarks with cargo bench.

SILK Encoder (Rust, complexity=0)

Sample Rate	Frame Size	Time per Frame	Throughput
8 kHz	20 ms	13.6 µs	22.4 MiB/s
16 kHz	20 ms	25.2 µs	24.2 MiB/s
16 kHz	10 ms	13.9 µs	22.0 MiB/s

SILK vs C Reference (libopus)

Config	8kHz/20ms	16kHz/20ms	16kHz/10ms
Rust (cx0)	15.1 µs	25.2 µs	13.9 µs
C libopus (cx0)	14.6 µs	18.3 µs	11.4 µs
C libopus (cx9)	67.7 µs	130.8 µs	66.2 µs

Rust implementation uses complexity=0 (fast mode). Performance is comparable to C at the same complexity level. C at complexity=9 (default quality) is 4-5x slower.

SILK Core Algorithms

Function	Time (16kHz WB)
burg_modified_fix	3.1 µs
autocorrelation	~0.5 µs
inner product	~0.2 µs

License

This project is a clean-room Rust port of the Opus reference implementation. See COPYING for the original Opus license (BSD-3-Clause).

Links

• Rustpbx: https://github.com/restsend/rustpbx