# AudioKit

## Welcome to AudioKit

Your guide to understanding the codebase

### Learning Path

16 units • 5 levels

### Orchestration & APIs

- Pipelines, workflows, public interfaces • 4 units

### AudioEngine Core & Node Architecture

- Architecture·5

### Audio Engine Core & Node Protocol

- Architecture·4

### Audio File Processing & Timing

- Data Model·5

### Basic Audio Playback & Recording

- Workflow·10

### Core Logic & Data

- Business rules, schemas, models • 3 units

### Signal Routing & Mixing

- Architecture·5

### MIDI Fundamentals

- Patterns·28

### Audio Processing & Effects

- Workflow·6

### Interaction & Integration

- UI components, external connectors • 2 units

### MIDI Integration & Synchronization

- Integration·8

### Sequencing & Synthesis

- Workflow·5

### Cross-Cutting Concerns

- Auth, logging, config, testing • 2 units

### Production & Deployment

- Infrastructure·7

### Analysis & Rendering

- Workflow·5

### Edge Cases & Resilience

- Error handling, fault tolerance • 2 units

### Additional Data Model Patterns

- Data Model·10

### Additional Error Handling Patterns

- Error Handling·5

## Test Your Knowledge

Test your deep understanding of the codebase

### Question Tiers

- **Why** 8
- **Purpose & Problem** Architecture 10
- **Design & Patterns** Code 8
- **Implementation**

## Hands-On Assignment

2-3 hours

### Your Challenge

Build a real-time audio visualizer node that analyzes incoming audio and generates frequency spectrum data that can be used to drive visual displays. Your node should:
- Tap into the audio engine's processing chain
- Perform FFT analysis on the audio buffer
- Expose frequency bins through a callback mechanism
- Follow AudioKit's node architecture patterns
- Work seamlessly with existing audio players and effects

### Starting Points

```bash
Package.swift:1-17
```
Examine the package structure and dependencies to understand how AudioKit is organized and what audio processing capabilities are available.

```bash
Sources/AudioKit/Nodes/
```
Explore existing node implementations to understand the base node architecture, how nodes connect to the audio engine, and how they process audio buffers.

```bash
Sources/AudioKit/Nodes/Effects/
```
Study how effect nodes tap into the audio stream without interrupting playback - your visualizer should work similarly.

```bash
Sources/AudioKit/Nodes/Analysis/
```
This is where you'll create your new FFTVisualizerNode class that performs frequency analysis.

```bash
Sources/AudioKit/AudioEngine.swift
```
Understand how nodes attach to the engine and how audio buffers flow through the processing chain.

### Success Criteria

- Node can be inserted into an audio chain without affecting audio playback quality
- Frequency spectrum data (array of magnitude values) is delivered via callback at regular intervals
- Works with both audio file playback and live microphone input
- FFT size is configurable (support at least 1024, 2048, and 4096 sample windows)
- No audio dropouts or glitches occur during visualization
- Example playground or test app demonstrates the visualizer with a simple bar graph display
- Memory usage remains stable during extended operation (no leaks)

### Hints

- **Hint 1:** Understanding AudioKit's node architecture conceptual
- **Hint 2:** FFT processing in audio context implementation
- **Hint 3:** Real-time callback pattern implementation
- **Hint 4:** Integration with existing audio chain code location
- **Hint 5:** Performance considerations implementation

### Prerequisites

- Audio buffer processing
- FFT fundamentals
- Swift closures and callbacks
- AVFoundation basics