Skip to content

THIRD_PARTY.md

Latest commit

 

History

History
51 lines (42 loc) · 2.8 KB

THIRD_PARTY.md

File metadata and controls

51 lines (42 loc) · 2.8 KB
Raw

Third-party provenance

go-opus is a native Go port of the Opus audio codec. Unlike a clean-room reimplementation, the codec logic here is a deliberate transliteration of libopus: the decoder is specified by RFC 6716, but the encoder is not specified by any RFC, so libopus is effectively the specification and the only sane route is a faithful port of it. go-opus is therefore a derivative work of libopus and is licensed under the same 3-clause BSD license (see LICENSE).

libopus (BSD 3-clause, transliteration reference)

  • Upstream: https://gitlab.xiph.org/xiph/opus (GitHub mirror: xiph/opus).
  • Transliteration reference pinned at tag v1.6.1. Doc line numbers in docs/ cite commit 3da9f7a6 (v1.6.1+50); expect a few lines of drift against the tag.
  • Every transliterated Go file keeps the upstream libopus BSD 3-clause copyright header. The frozen build configuration ported is FIXED_POINT + DISABLE_FLOAT_API, with no QEXT/RES24/dnn/CUSTOM_MODES.
  • Opus is an IETF codec with royalty-free patent grants (see LICENSE for the IPR links). A reimplementation/port is clean with respect to those grants.
  • The pinned libopus sources live under internal/reftest as a git submodule and are built only by the cgo differential-test harness (build tag refc); they are never compiled into the published pure-Go module.

SIMD

  • github.com/tphakala/simd (MIT, same author) is a runtime dependency. It backs the two hot pitch kernels (celt_inner_prod and xcorr_kernel) through i16.DotProduct and i16.XCorr, and the radix-3/radix-5 FFT butterflies (kiss_fft.go) through the cint fixed-point complex ops (cint.Mul / Add / Sub / MulByScalar), mirroring the go-flac scalar-reference-plus-SIMD structure. The library is pure Go plus its own per-arch assembly (SMLAL/SMLAL2 on arm64, PMADDWD/AVX2 on amd64) and has no cgo; it pulls golang.org/x/sys (indirect, also cgo-free) for CPU-feature detection. Each kernel keeps a scalar reference (internal/celt/pitch_ref.go for pitch, the frozen *Scalar butterflies for the FFT) that the library results are asserted bit-exact against (internal/celt/pitch_simd_test.go, internal/celt/fft_cint_oracle_test.go).

Test corpus and conformance vectors

  • RFC 6716 / RFC 8251 official Opus test vectors: fetched and sha256-verified by scripts/fetch-vectors.sh, used for testing only, never committed (see .gitignore and testdata/vectors.sha256). RFC 8251 is the archive that matters; it only revised the .dec reference outputs.
  • Local corpus (bird recordings, speech, music, sine sweeps, silence, noise) is used by differential tests and is not committed.

Ruleguard DSL

  • github.com/quasilyte/go-ruleguard/dsl (BSD 3-clause): build-time-only dependency backing the custom gocritic ruleguard matchers in rules/. Anchored by tools/tools.go; never compiled into the module.