LUFS Generator for Android

Cross-compiled Rust binary that calculates LUFS (Loudness Units Full Scale) for audio files on Android using streaming audio decoders.

Prerequisites

• Android NDK (tested with 23.2.8568313)
• Rust toolchain

Build Steps

Step 1: Set environment variables

export NDK_HOME=/path/to/android-ndk
export CC_aarch64_linux_android=${NDK_HOME}/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android29-clang
export CARGO_TARGET_AARCH64_LINUX_ANDROID_LINKER=${NDK_HOME}/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android29-clang

Step 2: Build Rust Binary

cargo build --release --target aarch64-linux-android

The binary will be at: target/aarch64-linux-android/release/lufsgen

Step 3: Deploy to Android

scp -P 8022 target/aarch64-linux-android/release/lufsgen 192.168.136.29:~/
# or with adb
adb push target/aarch64-linux-android/release/lufsgen /data/local/tmp/
adb shell chmod 755 /data/local/tmp/lufsgen

Step 4: Run on Android

# Calculate LUFS for a single file
~/lufsgen /sdcard/music.mp3

# Scan a directory
~/lufsgen /sdcard/Music

# Save results to file
~/lufsgen /sdcard/Music /sdcard/lufs_results.txt

Usage

lufsgen <audio-file>          Calculate LUFS for a single file
lufsgen <directory>           Scan directory for audio files
lufsgen <file/dir> <output>   Save results to file

Output Format

The binary outputs filename|lufs per line:

song.mp3|-12.5
track2.wav|-10.3

Supported Audio Formats

• MP3 (.mp3)
• WAV (.wav)
• AAC (.aac, .m4a, .mp4)
• OGG (.ogg, .oga)
• FLAC (.flac)

How It Works

This project uses Symphonia, a pure Rust multimedia framework, to decode audio files. The streaming decoder:

1. Auto-detects audio format from file content (not just extension)
2. Decodes audio chunk-by-chunk (8192 samples per chunk)
3. Feeds samples to EBU R128 loudness analyzer
4. Returns the integrated LUFS value

This approach is memory-efficient and suitable for mobile devices.

Desktop Testing

cargo build --release
cargo run --release -- /path/to/music.mp3

Troubleshooting

Build fails

Make sure the NDK path is correct and the clang compiler exists:

ls ${NDK_HOME}/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android29-clang

Permission denied

Make the binary executable:

adb shell chmod 755 /data/local/tmp/lufsgen

Library Usage

This is also a library that can be used in other Rust projects:

use lufsgen::{LufsCalculator, is_audio_file};

// Check if file is supported
if is_audio_file("song.mp3") {
    // Calculate LUFS
    let lufs = LufsCalculator::new().calculate_from_file("song.mp3")?;
    println!("LUFS: {}", lufs);
}

See lib.rs for the full API documentation.