mousiki

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

Current coverage (high level)

• Opus decode path mirrors opus_decode_native, including SILK/CELT/Hybrid, PLC/FEC, final-range reporting, and packet parsing; multistream decode and projection front-ends are wired.
• Opus encode front-end supports SILK-only 10/20/40/60 ms packets (plus repacketized

  60 ms frames), CELT-only multiframe packing, and hybrid single-frame 10/20 ms payloads.

• Repacketizer, packet helpers, extension padding, mapping/projection matrices, and tonality analysis are available.

Known gaps

• Full encoder parity (hybrid multiframe, full CELT/HYBRID packing, remaining CTLs) is still pending.
• Fixed-point decode backend, SIMD back-ends, and optional DRED/Deep PLC paths are not complete.
• See PORTING_STATUS.md for detailed status.

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 --example playback -- testdata/tiny.ogg

Run the tests

• Full test suite:

cargo test --all-features

• 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 snippet below uses the lightweight decoder::Decoder (SILK-only, single-frame) to decode a single Opus packet into i16 PCM (mono, 48 kHz):

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:

use mousiki::decoder::Decoder;

let packet: &[u8] = /* your Opus packet */;
let mut pcm_f32 = [0.0f32; 960];

let mut decoder = Decoder::new();
let (_bandwidth, stereo) = decoder.decode_float32(packet, &mut pcm_f32)?;
assert!(!stereo);

Tip: If you need the full Opus API surface (stereo, CELT/Hybrid, multistream), use opus_decoder instead of decoder::Decoder. For Ogg input, see the oggreader example to extract raw Opus packets.

Compatibility and roadmap

• Target environments: no_std + alloc, constrained memory, real-time systems.
• The decoder::Decoder path remains SILK-only and single-frame; the full Opus API surface is exposed via opus_decoder/opus_encoder.
• For detailed porting milestones, see PORTING_STATUS.md.

License and acknowledgements

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