Realtime BPM Analyzer

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What is Realtime BPM Analyzer? ​

Realtime BPM Analyzer is a powerful, dependency-free TypeScript/JavaScript library that enables you to detect the beats-per-minute (BPM) or tempo of audio and video sources directly in the browser.

Key Features ​

🎵 Real-Time Analysis ​

Analyze BPM while audio or video is playing. Get instant feedback with both continuous updates and stable BPM detection events.

⚡ Zero Dependencies ​

Built entirely on the Web Audio API with no external dependencies. This keeps the library lightweight (< 5KB gzipped) and ensures compatibility across modern browsers.

🎯 Accurate Detection ​

Uses an advanced algorithm based on:

  • Amplitude threshold scanning - Detects peaks in the audio signal
  • Interval analysis - Identifies patterns in peak timing
  • Tempo grouping - Groups similar tempos and selects the best candidates

🎬 Multiple Input Sources ​

Works with various audio sources:

  • HTML <audio> and <video> elements
  • File uploads (MP3, FLAC, WAV)
  • Microphone/getUserMedia streams
  • Network audio streams
  • Any source compatible with Web Audio API

📦 TypeScript Support ​

Written in TypeScript with complete type definitions for excellent IDE integration and type safety.

How It Works ​

The library analyzes audio data in real-time using the Web Audio API's AudioWorkletProcessor. Here's a simplified flow:

  1. Audio Input → Audio is captured from your source
  2. Filtering → Optional low-pass filter to isolate bass frequencies
  3. Peak Detection → Identifies peaks in the audio signal at various threshold levels
  4. Interval Analysis → Calculates time intervals between peaks
  5. BPM Calculation → Converts intervals to BPM and groups similar tempos
  6. Result Output → Emits BPM candidates with vote counts and a confidence share

Use Cases ​

Perfect for:

  • 🎧 DJ Applications - Auto-sync tracks, beatmatching
  • 🎵 Music Players - Display current track tempo
  • 📊 Audio Visualization - Sync visuals to detected BPM
  • 💪 Fitness Apps - Match workout intensity to music tempo
  • 🎹 Music Production Tools - Analyze and catalog track tempos
  • 🎪 Interactive Experiences - Create tempo-reactive installations

Browser Support ​

Works in all modern browsers that support:

  • ✅ Web Audio API
  • ✅ AudioWorklet

TIP

For older browser support, consider using a polyfill or fallback strategy.

Next Steps ​

Ready to get started?