Android USB Audio Recorder Context

This skill provides specialized guidance for developing an Android USB audio recorder application focused on 384kHz high-frequency recording and real-time ultrasonic visualization, inspired by BatRecorder app analysis.

Project Description

A new Android application for high-frequency USB audio recording (384kHz sampling rate) with real-time visualization, specifically designed for ultrasonic and bat call recording applications. The project integrates Android USB Host APIs with native C++ processing for optimal performance.

Key Technical Capabilities

USB Audio Architecture

Audio Processing Pipeline

Custom Visualization Components

Instructions for AI Agent

When working on this project, follow these guidelines:

1. Project Structure Understanding

**Primary source directory:** `app/src/main/java/com/example/usbaudio/`

**Core components to modify:**

**Reference materials (read-only):**

2. Code Development Guidelines

**When modifying existing code:**

**When adding features:**

**Native method integration pattern:**

```java

// Declare native methods in MainActivity/Service

private native int ReadFrameFromAudioBuffer();

private native void StartRecord(String filename);

private native void StopRecord();

private native float[] analyzeSpectrum(short[] audioData);

```

3. Critical Technical Requirements

**USB Audio Configuration:**

**Real-Time Performance:**

**Android Requirements:**

4. Current Development Priorities

**Phase 1 (Completed):**

✅ Basic USB audio infrastructure

✅ 384kHz spectrogram visualization

✅ USB Host mode integration

✅ Release APK build system

**Phase 2 (In Progress):**

**Phase 3 (Future):**

5. Testing and Validation

**Required test cases:**

**Performance benchmarks:**

6. Code Quality Standards

**When reading decompiled reference code:**

**When writing new code:**

7. Build and Release Process

**Build outputs:** `release/` directory contains distribution APKs

**Release checklist:**

8. Common Pitfalls to Avoid

Example Usage Scenarios

**Scenario 1: Adding new FFT library**

```

User: "Integrate KissFFT for better performance"

AI should:

1. Read current FFT implementation in native code

2. Add KissFFT dependency to CMakeLists.txt

3. Create JNI wrapper for KissFFT functions

4. Update analyzeSpectrum() native method

5. Benchmark performance vs. current O(N²) implementation

6. Update SpectrogramView to handle new spectrum data format

```

**Scenario 2: Implementing trigger-based recording**

```

User: "Add amplitude threshold triggering"

AI should:

1. Review current recording flow in UsbAudioService

2. Add threshold configuration UI in MainActivity

3. Implement native peak detection in audio buffer reader

4. Add recording state machine (armed/triggered/stopped)

5. Update UI indicators for trigger status

6. Test with synthetic ultrasonic signals

```

Constraints

Additional Notes

This project requires understanding of:

When uncertain about hardware-specific behavior, consult Android USB documentation and test with physical USB audio devices supporting 384kHz sample rates.