# Raspberry Pi Real-Time Audio Mixer

RPi4B-based multi-channel real-time audio mixer with custom PREEMPT_RT kernel.

## Architecture

- **Platform:** Raspberry Pi 4 Model B (8GB RAM)
- **OS:** Raspberry Pi OS Lite (64-bit, Bookworm) + custom PREEMPT_RT kernel
- **Audio:** USB audio interface with multi-channel I/O
- **Goal:** Low-latency (<10ms round-trip) multi-channel audio mixing

## Project Structure

```
├── docs/           Research, architecture decisions, manuals
│   ├── research/   Technical research reports
│   ├── decisions/  Architecture Decision Records (ADRs)
│   └── manuals/    Hardware/software manuals and references
├── src/            Source code (audio engine, DSP, UI)
├── build/          Build scripts and cross-compilation tooling
├── recipes/        Buildroot/Yocto recipes (if applicable)
├── scripts/        Utility and deployment scripts
└── wiki/           Local wiki pages
```

## Status

**Phase 1-7: Complete audio mixer stack with SD card image builder**

- [x] P1-R1: System Research — USB audio, PREEMPT_RT kernel analysis
- [x] P1-R2: Base OS Selection — RPiOS Lite 64-bit + custom PREEMPT_RT
- [x] P2-R1: ALSA + JACK2 Low-Latency Config
- [x] P3-R1: Core Mixer Engine — DSP pipeline, channel strips, routing
- [x] P3-R2: Backing Track Player — sync'd audio playback
- [x] P3-R3: Multi-Track Recording — WAV capture + session
- [x] P4-R1: MIDI Controller Support — Binding + Learn Mode
- [x] P5-R3: Web App Frontend — touch-optimized mixer UI
- [x] P6-R1: Streaming Pipeline — GStreamer H.264 to YouTube/Twitch
- [x] P6-R2: Session Manager — save/load mixer states + setlists
- [x] P7-R1: Build Script — automated SD card image creation

## SD Card Image Builder

```bash
# Build a ready-to-flash SD card image
./build/build.sh --skip-kernel    # Quick build (10-15 min)
./build/build.sh                  # Full build with RT kernel (30-45 min)
```

See [build/README.md](build/README.md) for flashing instructions and full documentation.

## Getting Started

*Documentation coming in Phase 2+*

## License

TBD