opus-rs 0.1.4

pure Rust implementation of Opus codec
Documentation

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 all benchmarks:

cargo bench

Run a specific benchmark:

cargo bench -- silk_pitch_analysis_core  # Pitch analysis only
cargo bench -- silk_nsq               # Noise shape quantizer
cargo bench -- silk_burg_modified_fix  # LPC analysis

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) Time (8kHz NB)
burg_modified_fix 3.1 µs —
autocorrelation ~0.5 µs ~0.2 µs
inner product ~0.2 µs ~0.1 µs
pitch_analysis_core 7.5 µs 3.1 µs
nsq (voiced) 8.3 µs 4.4 µs
nsq (unvoiced) 6.9 µs 3.5 µs

License

See COPYING for the original Opus license (BSD-3-Clause).

Links