bbx_dsp

A block-based audio DSP system for building signal processing graphs.

Features

• Graph-based architecture: Connect blocks to form processing chains
• Generic sample type: Works with f32 or f64 precision
• Realtime-safe processing: Stack-allocated buffers, no allocations in audio thread
• Parameter modulation: LFOs and envelopes can modulate block parameters
• Parameter smoothing: Click-free parameter changes with configurable ramp times via set_smoothing()
• Topological sorting: Automatic execution order based on connections

Block Types

Generators

• OscillatorBlock - Waveform generator (sine, square, saw, triangle, pulse, noise)

Effectors

• GainBlock - Level control in dB
• OverdriveBlock - Asymmetric soft-clipping distortion
• PannerBlock - Stereo, surround (VBAP), and ambisonic panning
• DcBlockerBlock - DC offset removal
• ChannelRouterBlock - Simple stereo channel routing
• ChannelSplitterBlock - Split multi-channel to mono outputs
• ChannelMergerBlock - Merge mono inputs to multi-channel
• MatrixMixerBlock - NxM mixing matrix
• AmbisonicDecoderBlock - Ambisonics B-format decoder
• BinauralDecoderBlock - Ambisonics B-format to stereo binaural for headphones
• LowPassFilterBlock - SVF-based TPT low-pass filter with cutoff/resonance

Modulators

• LfoBlock - Low-frequency oscillator for parameter modulation
• EnvelopeBlock - ADSR envelope generator

I/O

• FileInputBlock - Read audio from files
• FileOutputBlock - Write audio to files (non-blocking I/O)
• OutputBlock - Terminal graph output

Multi-Channel System

Beyond basic stereo, bbx_dsp supports surround and ambisonic formats:

Channel Layouts

• Mono - 1 channel
• Stereo - 2 channels (default)
• Surround51 - 6 channels (5.1)
• Surround71 - 8 channels (7.1)
• AmbisonicFoa - 4 channels (1st order)
• AmbisonicSoa - 9 channels (2nd order)
• AmbisonicToa - 16 channels (3rd order)
• Custom(n) - Arbitrary channel count

Channel Config

Blocks declare how they handle multi-channel audio:

• Parallel (default) - Process each channel independently
• Explicit - Block handles routing internally (panners, mixers, decoders)

Use GraphBuilder::with_layout() to create graphs with specific channel configurations.

Cargo Features

simd

Enables SIMD optimizations for supported blocks. Requires nightly Rust.

[dependencies]
bbx_dsp = { version = "...", features = ["simd"] }

Optimized blocks:

• OscillatorBlock - Vectorized waveform generation
• LfoBlock - Vectorized modulation signal generation
• GainBlock - Vectorized gain application

PluginDsp Trait

For plugin integration, implement PluginDsp with optional MIDI support:

• process() receives midi_events: &[MidiEvent] parameter
• Override note_on(), note_off(), control_change(), pitch_bend() for MIDI handling

Benchmarking

Run performance benchmarks to measure SIMD optimization effectiveness:

# Scalar baseline
cargo bench --benches -p bbx_dsp -- --save-baseline scalar

# SIMD comparison (requires nightly)
cargo +nightly bench --benches -p bbx_dsp --features simd -- --save-baseline scalar

HTML reports are generated in target/criterion/. See the full documentation for details.

Usage

use bbx_dsp::{graph::GraphBuilder, waveform::Waveform};

// Create a graph with 44.1kHz sample rate, 512 sample buffer, stereo output
let mut builder = GraphBuilder::<f32>::new(44100.0, 512, 2);

// Add an oscillator
let osc = builder.add_oscillator(440.0, Waveform::Sine, None);

// Build the graph (automatically adds output block)
let mut graph = builder.build();

// Process audio
let mut left = vec![0.0f32; 512];
let mut right = vec![0.0f32; 512];
let mut outputs: [&mut [f32]; 2] = [&mut left, &mut right];
graph.process_buffers(&mut outputs);

License

MIT