mousiki

A Rust port of the Xiph opus-c reference implementation. The core crate is #![no_std] and uses alloc (some APIs allocate).

Known gaps

Fixed-point decode backend

Quick start

Run the examples

Decode Ogg Opus (SILK-only path used by decoder::Decoder) to a PCM file:

cargo run --example decode -- testdata/tiny.ogg output_mono.pcm

Play directly (requires an audio output device; uses cpal):

cargo run -p playback -- testdata/tiny.ogg

Round-trip a full 48 kHz stereo PCM sample through the trivial encoder/decoder:

cargo run --example trivial_example -- \
  testdata/ehren-paper_lights-96.pcm ehren-paper_lights-96_trivial_out.pcm

Convert the raw PCM output to WAV for playback:

ffmpeg -y -f s16le -ar 48000 -ac 2 \
  -i ehren-paper_lights-96_trivial_out.pcm \
  ehren-paper_lights-96_trivial_out.wav

Run the tests

Full test suite:

cargo test --all-features

Default-build golden regression check for the trivial 48 kHz stereo round-trip configuration:

cargo test --test trivial_example trivial_example_default_build_golden_hash

Decode integration test (ported from opus-c/tests/test_opus_decode.c):

cargo test --all-features --test test_opus_decode

Opt-in to the fuzz-heavy decode section (longer runtime), or to strict final-range checks:

TEST_OPUS_FUZZ=1 cargo test --all-features --test test_opus_decode
TEST_OPUS_STRICT_FINAL_RANGE=1 cargo test --all-features --test test_opus_decode

DRED vector validation (optional; vectors are distributed separately):

# Fetch vectors into testdata/dred_vectors (requires DRED_VECTORS_URL).
./scripts/fetch_dred_vectors.sh --url <vector-archive-url>

# Run the vector checks (uses DRED_VECTORS_PATH or testdata/dred_vectors).
# If deep_plc_weights is disabled, set DNN_BLOB or pass --dnn-blob.
DRED_VECTORS_PATH=testdata/dred_vectors cargo test --all-features --test dred_vectors

Fuzzing (manual/on-demand)

Fuzzing uses cargo-fuzz and is not part of CI by default.

cargo install cargo-fuzz
rustup toolchain install nightly
rustup run nightly cargo fuzz run decode_fuzzer

Seed corpus lives in fuzz/corpus/decode_fuzzer/.

Use in your code

The preferred high-level API is exported at the crate root and wraps the full Opus front-end (SILK/CELT/Hybrid, stereo) with typed enums and method-based state:

use mousiki::{Application, Bitrate, Channels, Decoder, Encoder};

const SAMPLE_RATE: u32 = 48_000;
const FRAME_SIZE: usize = 960;
const MAX_FRAME_SIZE: usize = 6 * 960;
const MAX_PACKET_SIZE: usize = 3 * 1276;

let mut encoder = Encoder::builder(SAMPLE_RATE, Channels::Stereo, Application::Audio)
    .bitrate(Bitrate::Bits(64_000))
    .build()?;
let mut decoder = Decoder::new(SAMPLE_RATE, Channels::Stereo)?;

let pcm_in = [0i16; FRAME_SIZE * Channels::Stereo.count()];
let mut packet = [0u8; MAX_PACKET_SIZE];
let packet_len = encoder.encode(&pcm_in, &mut packet)?;

let mut pcm_out = [0i16; MAX_FRAME_SIZE * Channels::Stereo.count()];
let decoded = decoder.decode(&packet[..packet_len], &mut pcm_out, false)?;
let total_samples = decoded * Channels::Stereo.count();
let _decoded_pcm = &pcm_out[..total_samples];

If you need API parity with the C entry points, use mousiki::c_style_api::*.

If you only need the lightweight SILK-only, single-frame decoder (mono, 48 kHz), use decoder::Decoder directly:

use mousiki::decoder::Decoder;

// `packet` is a single Opus SILK-only, mono packet (already decontainerized; not an Ogg page).
let packet: &[u8] = /* your Opus packet */;

// Output buffer (20 ms -> 960 samples, each sample is 2 bytes for i16)
let mut pcm_bytes = [0u8; 1920];

let mut decoder = Decoder::new();
let (_bandwidth, stereo) = decoder.decode(packet, &mut pcm_bytes)?;
assert!(!stereo, "mono only for now");
// `pcm_bytes` now contains 48 kHz i16 little-endian PCM data

For f32 output, use decode_float32 and a buffer of length 960 for a 20 ms frame. For Ogg input, see the decode example and the mousiki::oggreader module to extract raw Opus packets.

License and acknowledgements

License: MIT (see LICENSE).
Thanks to the upstream pion/opus (Go) implementation and the community.

mousiki 0.2.0