Composables & protocol

The data pipelines are also available standalone, if you want to drive your own rendering or combine them with mode="external".

useLocalAudio(options?)

Captures mic or display audio and runs the WASM FFT.

const {
  fftData,        // Ref<Uint8Array> — magnitudes 0–255
  isActive, sourceType, devices, activeDeviceId,
  getDevices,     // () => Promise<AudioDevice[]>
  start,          // (deviceId?) => Promise<void>  — microphone
  startDisplay,   // () => Promise<void>           — tab/system audio
  stop
} = useLocalAudio({ fftSize: 2048, bins: 80, startFreq: 100, endFreq: 18000 })

useWebSocketFft(options?)

Connects to a WebSocket that streams raw PCM and computes the FFT in-browser via WASM (distinct from the component's websocket mode, which expects pre-computed FFT). Feed its fftData into the component with mode="external".

const {
  fftData, fftDataLeft, fftDataRight, isConnected,
  connect,        // (url) => void
  disconnect,
  processSamples  // (Float32Array) => void — feed PCM manually
} = useWebSocketFft({ fftSize: 2048, bins: 80, overlap: 0.5, autoReconnect: true })

The raw WASM FFT processor is also exported from vue-fft-visualizer/wasm for direct use.

WebSocket protocol

mode="websocket" expects a server that sends pre-computed FFT frames.

1. Config message (JSON), once on connect:

{ "type": "config", "mode": "fft", "bins": 80, "fps": 120 }

2. Binary FFT frames, continuously:

• One uint8 (0–255) per frequency bin — bins bytes per frame
• 0 = silence, 255 = maximum amplitude
• Typically 100 Hz – 18 kHz, exponentially spaced

For best results the server should capture at 48 kHz+, apply a Hann/Hamming window, compute a 1024–2048-point FFT, map to exponentially-spaced bands, apply A-weighting, convert to dB, normalize to 0–255, and stream at 60–120 fps.

Reference servers

The repository's backend-examples/ has servers that capture system audio, compute FFT, and stream it: Python (pyalsaaudio + numpy, incl. a Raspberry Pi variant), Node.js (node-audiorecorder + fft.js), and Rust (cpal + rustfft).