sonicLens

An audio recognition and music discovery system using audio fingerprinting to identify songs from a Spotify-backed catalog — similar to Shazam, but self-hosted.

Overview

sonicLens lets you upload an audio clip and identify the matching song from a catalog you build from Spotify. It uses FFT-based combinatorial hashing for fingerprinting, similar to the Shazam algorithm.

Key features:

• Audio recognition with confidence scoring
• Song catalog built from Spotify tracks, albums, or playlists
• Full-track audio streaming via a Go/librespot microservice
• Spotify OAuth integration for user authentication and playback
• Recognition history per user
• JWT-authenticated REST API

Architecture

┌─────────────────────────────────┐
│  Client (Browser / API consumer)│
└──────────────┬──────────────────┘
               │
   ┌───────────▼────────────┐     ┌─────────────────────┐
   │  Spring Boot REST API  │────▶│  Go Microservice    │
   │  Java · Port 8082      │     │  Port 8888          │
   │                        │◀────│                     │
   │  - JWT auth            │     │  - Spotify full-    │
   │  - Audio fingerprinting│     │    track streaming  │
   │  - Recognition logic   │     │  - librespot OAuth  │
   │  - Spotify API bridge  │     │  - WAV encoding     │
   │  - Song/history mgmt   │     └─────────────────────┘
   └───────┬────────────────┘
           │
     ┌─────┴──────┐   ┌───────────────────┐
     │ PostgreSQL │   │  GCP Cloud Storage│
     └────────────┘   └───────────────────┘

Prerequisites

• Java 17+
• Go 1.21+
• PostgreSQL
• pkg-config and librespot native dependencies (see Go service setup)
• A Spotify Developer app (Client ID + Secret)
• (Optional) GCP project with Cloud Storage

Getting Started

1. Go Microservice (librespot-service)

The Go service handles full-track audio streaming from Spotify. It must be running before the Spring Boot app starts.

cd librespot-service
PKG_CONFIG_PATH="/opt/homebrew/lib/pkgconfig" go run .

On first run, a browser window opens for Spotify OAuth login. Credentials are saved to ~/.sonicLens/go-librespot/credentials.json and reused on subsequent starts.

Run with pm2 (recommended for persistent deployments):

# Start
pm2 start "go run ." --name librespot-service

# For faster restarts, build a binary first
go build -o librespot-service .
pm2 start ./librespot-service --name librespot-service

Useful pm2 commands:

pm2 list                        # see all running services
pm2 logs librespot-service      # tail logs
pm2 restart librespot-service   # restart
pm2 stop librespot-service      # stop

2. Spring Boot API

Configure src/main/resources/application.properties:

# Database
spring.datasource.url=jdbc:postgresql://<host>:5432/<db>
spring.datasource.username=<user>
spring.datasource.password=<password>

# Spotify
spotify.client-id=<your-client-id>
spotify.client-secret=<your-client-secret>
spotify.redirect-uri=http://<host>:8082/callback

# Go service (must match where librespot-service is running)
librespot.service.url=http://localhost:8888

# JWT
jwt.secret=<your-secret>

# GCP (optional)
gcp.storage.bucket-name=<bucket>
gcp.storage.project-id=<project>

Then build and run:

./gradlew bootRun

The API will be available on port 8082.

API Reference

Authentication

Method	Endpoint	Auth	Description
POST	/auth/register	—	Create a user account
POST	/auth/login	—	Get a JWT token
GET	/auth/spotify	JWT	Get Spotify OAuth authorization URL
GET	/callback	—	Spotify OAuth redirect handler
GET	/auth/spotify/token	JWT	Get/refresh Spotify access token

Song Catalog

Method	Endpoint	Auth	Description
POST	/songs/add	JWT	Add song by Spotify track ID
POST	/songs/add-url	JWT	Add from Spotify track/album/playlist URL
GET	/songs/search?q=	—	Search Spotify
POST	/songs/upload	JWT	Upload a local audio file
POST	/songs/seed	JWT	Bulk-seed catalog from Spotify featured/new releases
GET	/songs	—	List all songs in catalog
GET	/songs/get/{id}	—	Get song by ID

Recognition

Method	Endpoint	Auth	Description
POST	/recognize	JWT	Upload an audio clip for identification

History

Method	Endpoint	Auth	Description
GET	/history	JWT	Get current user's recognition history
DELETE	/history/{id}	JWT	Delete a history entry

Users

Method	Endpoint	Auth	Description
GET	/users/me	JWT	Get current user info
GET	/users/{id}	—	Get user by ID

Admin

Method	Endpoint	Auth	Description
GET	/admin/librespot/status	—	Check Go service readiness
POST	/admin/librespot/reconnect	—	Trigger Spotify re-authentication

Fingerprinting Algorithm

sonicLens uses a Shazam-style combinatorial hash fingerprinting approach:

1. Decode any audio format to mono 16-bit PCM at 11,025 Hz
2. Spectrogram — 4,096-sample FFT with 50% overlap and Hann window
3. Peak detection — find peak magnitude across 6 log-scale frequency bands (40 Hz – 4 kHz)
4. Combinatorial hashing — pair each peak (anchor) with nearby peaks (target) within a time zone to create a hash encoding anchor frequency, target frequency, and time delta
5. Recognition — query the database for matching hashes, vote by (songId, timeDelta), and declare the winner above a 5% confidence threshold

Go Microservice Endpoints

The librespot service runs on port 8888:

Method	Endpoint	Description
GET	/status	Returns {"ready": bool}
POST	/reconnect	Clears credentials and triggers new OAuth login
GET	/stream/{trackId}	Streams full track as WAV (44.1 kHz, stereo, 16-bit PCM)

Tech Stack

Layer	Technology
Backend API	Java 17, Spring Boot, Spring Security (JWT)
Audio streaming	Go, go-librespot
Fingerprinting	JTransforms (FFT)
Database	PostgreSQL (JPA/Hibernate)
File storage	GCP Cloud Storage
Auth	JWT (JJWT), Spotify OAuth2
Build	Gradle
Process mgmt	pm2