DeltaSleep

Your sleep data stays in your bed.

Free, open-source Android app for sleep phase and snore tracking. Every byte of analysis happens on your device. The app ships without the INTERNET permission and a CI job verifies this on every commit.

Website · Changelog · F-Droid (planned)

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Features (v0.1 MVP)

Sleep phases	Awake / Light / Deep classified every 30 s via audio heuristics
Snore detection	Spectral band-power analysis (20–300 Hz), per-epoch yes/no flag
Hypnogram	On-device canvas chart, color-coded by phase
CSV export	Full epoch data to any folder via the system file picker
Zero network	No analytics, no crash reporting, no telemetry — ever

Privacy guarantees

• INTERNET permission is absent from the manifest
• CI fails if http, socket, URL, or fetch appear in source
• Only three permissions requested: RECORD_AUDIO, FOREGROUND_SERVICE, POST_NOTIFICATIONS
• Raw audio is never written to disk
• "Delete all data" overwrites the database before deletion

Architecture

Jetpack Compose UI
      │
      ▼
Room (SQLite, app-private)   ←   SleepTrackingService (foreground)
                                        │
                                        ▼
                              EpochProcessor (Kotlin)
                                        │
                                        ▼
                              DspBridge (JNI)
                                        │
                                        ▼
                       libdeltasleep_dsp.so  (Rust via NDK)
                       └── features.rs  (RMS · ZCR · IIR band-pass)
                       └── classifier.rs (Awake / Light / Deep)
                       └── snore.rs     (band-ratio threshold)

Audio is captured at 16 kHz in 10 ms frames. The Rust library accumulates features for 30 s, classifies the epoch, and discards the PCM. The foreground service writes one SleepEpoch row per 30 s to SQLite.

Building

Prerequisites

# Rust targets for Android
rustup target add aarch64-linux-android x86_64-linux-android
cargo install cargo-ndk

# Android NDK r26+ via Android Studio or sdkmanager
# Java 17 (Temurin recommended)

# Gradle wrapper (one-time, requires Gradle 8.6 on PATH)
gradle wrapper --gradle-version 8.6

Commands

# Build debug APK (also compiles Rust DSP automatically)
./gradlew :app:assembleDebug

# Install on connected device
./gradlew :app:installDebug

# Rust DSP only
cd dsp && cargo ndk -t arm64-v8a -t x86_64 -o ../app/src/main/jniLibs build --release

# Privacy check (must return no matches)
grep -rE '\b(http|socket|URL|fetch)\b' app/src/main/java/

Tech stack

Layer	Technology
UI	Kotlin + Jetpack Compose
Database	Room (SQLite)
DSP	Rust → .so via Android NDK
Build	Gradle 8.6 + cargo-ndk
Min SDK	Android 8.0 (API 26)

License

GPLv3 — if you improve it, everyone benefits. See LICENSE.