RustyOpus

Pure-Rust in-process audio conversion for Elixir. WAV, MP3, and Ogg Opus blobs are handled without C codecs, ffmpeg, Ports, or external processes; raw Opus packets remain available through the compatible packet API.

Headline: convert supported file blobs or metadata-carrying PCM with one small API:

{:ok, opus} = RustyOpus.convert(mp3_blob, to: :ogg_opus, bitrate: 20_000)
{:ok, wav} = RustyOpus.convert(opus, to: :wav, sample_format: :s16)
{:ok, pcm} = RustyOpus.convert(wav, to: :pcm)

That is the whole call. Useful bitrate ladder values: 8_000, 12_000, 16_000, 20_000, 24_000, 32_000.

Quick start

# Dedicated Ogg Opus re-encode retains its compatibility surface
{:ok, smaller} = RustyOpus.reencode(ogg_blob, bitrate: 20_000)

# WAV/MP3/Ogg Opus conversion uses content detection
{:ok, mp3} = RustyOpus.convert(wav_blob, to: :mp3, bitrate: 64_000, bitrate_mode: :vbr)
{:ok, pcm} = RustyOpus.convert(mp3, to: :pcm)

# Raw packets / PCM (no container)
{:ok, packets} = RustyOpus.encode(pcm, 16_000, 1, bitrate: 24_000)
{:ok, pcm}     = RustyOpus.decode(packets, 16_000, 1)

Data contract

• Ogg Opus — RFC 7845 family-0 binaries (audio/ogg / .ogg) for the dedicated module.
• MP3 — MPEG Layer III mono/stereo (audio/mpeg / .mp3), including bounded leading ID3.
• WAV — RIFF/WAVE uncompressed integer PCM or IEEE float (audio/wav / .wav).
• PCM — %RustyOpus.PCM{} carrying little-endian IEEE-754 f32, interleaved for stereo.
• Opus packets — raw binaries (no container), unchanged from earlier releases.

Metadata is not preserved, file paths and streaming are not supported, and only mono/stereo is accepted. WebM, MP4, AAC, FLAC, compressed WAV, and other Ogg mapping families remain out of scope. Never launches an external process. See the codec guide.

Features

• RustyOpus.convert/2 — common WAV/MP3/Ogg Opus/PCM conversion facade
• RustyOpus.WAV, RustyOpus.MP3, RustyOpus.OggOpus — dedicated three-verb file APIs
• RustyOpus.reencode/2 — backward-compatible Ogg Opus blob → lower bitrate Ogg Opus blob
• RustyOpus.encode/4, decode/4, transcode/5 — whole-stream raw packet/PCM path
• RustyOpus.Encoder / Decoder — per-frame control
• Dirty-scheduled codec work; panic containment at the NIF boundary
• Checksum-verified precompiled NIFs with source-build fallback

Supported OS

Precompiled NIFs are published for:

• Apple Silicon macOS (aarch64-apple-darwin)
• Intel macOS (x86_64-apple-darwin)
• ARM64 Linux glibc (aarch64-unknown-linux-gnu)
• ARM64 Linux musl / Alpine (aarch64-unknown-linux-musl)
• x86-64 Linux glibc (x86_64-unknown-linux-gnu)
• x86-64 Linux musl / Alpine (x86_64-unknown-linux-musl)

Other targets can build from source with RUSTY_OPUS_BUILD=1 and Rust 1.89.0.

Technology

Development

bin/qa_check.sh

Committed fixtures include an Ogg Opus speech blob for reencode/2 tests. Tests need neither a live database nor ffmpeg.

Release

1. Bump the version in mix.exs and native/rusty_opus_native/Cargo.toml.
2. Run bin/qa_check.sh and push the green version commit.
3. Tag v0.4.0; the release workflow builds and smoke-tests every precompiled NIF.
4. Publish the Hex package and GitHub release (maintainer step).

License

RustyOpus is licensed under the Apache License 2.0. Bundled codecs: opus-rs (BSD-3-Clause) and rusty_mp3 (Apache-2.0) — see NOTICE and provenance.