wdsp/README.md

WDSP

DSP library for SDR (Software Defined Radio) applications.

Originally written for Windows by Warren Pratt, NR0V. Ported to Linux and Android by John Melton G0ORX/N6LYT.

Project structure

wdsp/
├── *.c / *.h                    — WDSP library sources
├── org_openhpsdr_dsp_Wdsp.c/.h  — JNI bridge
├── Makefile                     — host build (Linux / macOS)
├── Makefile.android             — Android cross-build
├── java/
│   └── org/openhpsdr/dsp/Wdsp.java
├── third_party/
│   ├── fftw/              — FFTW source (download manually, see below)
│   ├── rnnoise/           — RNNoise noise suppression
│   └── libspecbleach/     — spectral noise reduction
├── obj/                   — object files (generated)
└── lib/                   — built libraries (generated)

---

Host build (Linux / macOS)

Dependencies

Linux:

sudo apt install build-essential libfftw3-dev pkg-config default-jdk

macOS:

brew install fftw pkg-config

Build

# Full build: static + shared + JNI library + Java classes
make

# Individual targets
make static        # lib/libwdsp.a
make shared        # lib/libwdsp.so  (or .dylib on macOS)
make java          # lib/libwdspj.so + java/build/

Install

sudo make install                    # installs to /usr/local/lib and /usr/local/include
sudo make PREFIX=/opt/wdsp install   # custom prefix
sudo make install_java               # install libwdspj alongside libwdsp

Options

Variable	Default	Description
PREFIX	/usr/local	Install prefix
NR34LIB	off	Set to ON to skip bundled rnnoise/libspecbleach
CC	gcc	C compiler
CFLAGS	-pthread -O3 ...	Compiler flags

make NR34LIB=ON    # build without NR3/NR4 noise reduction
make CC=clang

Clean

make clean

---

Android build

Prerequisites

1. Android NDK r23 or newer
2. FFTW source — download and extract into third_party/fftw/:

wget https://www.fftw.org/fftw-3.3.10.tar.gz
tar xf fftw-3.3.10.tar.gz
mv fftw-3.3.10 third_party/fftw

3. Java compiler — for building the .class file (Android Studio's JBR or any JDK)

Build

make android
# or directly
make -f Makefile.android

Output is placed into:

lib/android/
├── arm64-v8a/
│   ├── libfftw3.so
│   ├── libfftw3f.so
│   ├── libwdsp.so
│   └── libwdspj.so
├── armeabi-v7a/
│   └── ...
├── x86_64/
│   └── ...
└── java/
    └── org/openhpsdr/dsp/Wdsp.class

libwdsp.so has FFTW linked statically — no separate FFTW dependency at runtime on the device.

Options

Variable	Default	Description
ANDROID_NDK	/home/vladimir/Android/Sdk/ndk/29.0.14206865	Path to Android NDK
ANDROID_API	24	Minimum API level
ANDROID_ABIS	arm64-v8a armeabi-v7a x86_64	Target ABIs
ANDROID_HOST_TAG	auto-detected	Host platform (linux-x86_64, darwin-x86_64, etc.)
FFTW_SRC	third_party/fftw	Path to FFTW source
JAVAC	/opt/android-studio/jbr/bin/javac	Java compiler

make -f Makefile.android \
    ANDROID_NDK=~/Android/Sdk/ndk/26.3.11579264 \
    ANDROID_API=26 \
    ANDROID_ABIS=arm64-v8a

Clean

make -f Makefile.android clean
# removes obj/android/ and lib/android/

---

Using in an Android project

Copy lib/android/{abi}/ into your Android project's jniLibs:

app/src/main/jniLibs/
├── arm64-v8a/
│   ├── libwdsp.so
│   └── libwdspj.so
├── armeabi-v7a/
│   └── ...
└── x86_64/
    └── ...

Add Wdsp.java to your source tree and load the libraries at startup:

System.loadLibrary("wdsp");
System.loadLibrary("wdspj");

Or use the singleton:

Wdsp wdsp = Wdsp.getInstance();