Meshtastic Codec2 Android JNI

Open source speech codec designed for communications quality speech between 700 and 3200 bit/s. The main application is low bandwidth HF/VHF digital radio.

This repository contains the JNI (Java Native Interface) wrapper and build scripts to compile the Codec2 library for Android. It was developed to support the Voice Burst feature in the Meshtastic Android application.

This module has been isolated in its own repository and licensed under LGPL-2.1 to maintain strict compliance with the original Codec2 library licensing terms, allowing it to be dynamically linked by the GPLv3 Meshtastic application without licensing conflicts.

Architecture

This standalone library does not contain the core Android App code. It is responsible solely for:

1. Downloading the upstream Codec2 C source (v1.2.0).
2. Patching and executing CMake for the arm64-v8a and x86_64 Android ABIs.
3. Compiling the JNI wrapper (cpp/codec2_jni.cpp) which acts as the bridge between Android's Kotlin/JVM layer and the native C layer.
4. Exporting the libcodec2.so and libcodec2_jni.so binary files.

16 KB Page Alignment (Android 15+)

To ensure compatibility with modern Android 15 devices that enforce 16 KB page sizes, the script explicitly passes -Wl,-z,max-page-size=16384 to the linker.

How to Build

Prerequisites

• Android Studio or Command Line Tools installed.
• Android NDK (r25+ recommended).
• CMake installed via Android SDK Tools.
• Git for Windows/Linux/macOS.

Build Instructions

Run the automated build script:

cd scripts/
bash build_codec2.sh

The script will automatically:

1. Fetch Codec2 upstream.
2. Cross-compile libcodec2.so via Android CMake toolchains.
3. Compile libcodec2_jni.so using c++_static to avoid missing libc++ dependencies on the target Android devices.
4. Output the .so files for each ABI.

After the build, copy the generated .so files into the jniLibs/ directory of your Android application.

In the Meshtastic-Android fork, these .so files are bundled in the jniLibs directory, and dynamically loaded at runtime using:

System.loadLibrary("codec2_jni")

License

This project is licensed under the LGPL-2.1 license. See the LICENSE file for details.