lsp-plugins-rs

Rust port of lsp-plugins — professional audio DSP processing, exposed as GStreamer plugins.

Overview

┌─────────────────────────────────────────────────┐
│           gst-plugins-lsp (cdylib)              │
│  GStreamer audio processing elements            │
├─────────────────────────────────────────────────┤
│           lsp-dsp-units (lib)                   │
│  High-level DSP: compressor, EQ, limiter, ...   │
├─────────────────────────────────────────────────┤
│           lsp-dsp-lib (lib)                     │
│  Low-level primitives: FFT, biquad, dynamics    │
│  Runtime SIMD dispatch via multiversion         │
└─────────────────────────────────────────────────┘

Crates

Crate	Description
lsp-dsp-lib	Low-level DSP primitives with runtime SIMD dispatch (AVX2/FMA, AVX, SSE4.1, NEON) — FFT, biquad filters, dynamics curves, resampling, convolution
lsp-dsp-units	High-level DSP components — compressor, limiter, gate, expander, equalizer, meters, noise generators
gst-plugins-lsp	GStreamer plugin library (libgstlspdsprs.dylib) exposing DSP units as audio elements

GStreamer Elements

Plugin name: lspdsprs

Element	Description	Type
lsp-rs-compressor	Dynamics compressor with soft-knee and multiple modes	Filter
lsp-rs-gate	Noise gate with hysteresis	Filter
lsp-rs-limiter	Lookahead brickwall limiter	Filter
lsp-rs-expander	Dynamics expander (downward/upward)	Filter
lsp-rs-dither	TPDF dither for bit-depth reduction	Filter
lsp-rs-equalizer	Parametric equalizer with configurable bands	Filter
lsp-rs-meter	Peak, true-peak, and LUFS measurement	Analyzer
lsp-rs-crossover	Multi-band Linkwitz-Riley crossover filter	Filter
lsp-rs-noise	Noise generator (LCG, MLS, Velvet)	Source
lsp-rs-oscillator	Oscillator (sine, triangle, saw, square, pulse)	Source

Building

cargo build --release

Using the GStreamer Plugin

Point GStreamer at the built library:

export GST_PLUGIN_PATH=/path/to/target/release

# List all elements
gst-inspect-1.0 lspdsprs

# Inspect a specific element
gst-inspect-1.0 lsp-rs-compressor

# Example pipeline
gst-launch-1.0 audiotestsrc ! lsp-rs-compressor threshold=-20 ratio=4 ! autoaudiosink

Testing

# Run all tests
cargo test

# Run GStreamer plugin tests only
cargo test -p gst-plugins-lsp

The test suite includes A/B comparison tests against the original C++ implementation to verify numerical equivalence (ULP-based float comparison). The C++ reference is compiled via cc in two configurations: generic (-O2 -ffp-contract=off) for correctness tests and native-optimized (-O3 -march=native) for performance benchmarks.

Benchmarks

# High-level DSP processors: Rust vs upstream hand-tuned SIMD
cargo bench --bench ab_perf -p lsp-dsp-units --features upstream-bench

The upstream-bench feature links against the original lsp-dsp-lib hand-tuned SIMD library (SSE/AVX/NEON assembly) via git submodules in third_party/, enabling direct comparison of Rust high-level processors (compressor, gate, expander, EQ, meters) against upstream SIMD kernels.

Third-party Dependencies

The third_party/ directory contains git submodules used for upstream SIMD benchmarking:

Submodule	Source	Purpose
third_party/lsp-dsp-lib	lsp-plugins/lsp-dsp-lib (tag 1.0.33)	Hand-tuned SIMD DSP library
third_party/lsp-common-lib	lsp-plugins/lsp-common-lib (tag 1.0.38)	Common library dependency

These are only compiled when --features upstream-bench is enabled.

License

LGPL-3.0-or-later — same as the original lsp-plugins.