icytus/opencv-with-ffmpeg-on-qt-for-android

How to compile native/C++ OpenCV with FFmpeg support and use it on Qt for Android

Environment installation and compiling

Install CMake. Version 3.6.0 or higher is required. I got it from packages: apt install cmake.

Install Qt. I installed the latest stable version from Qt Maintenance Tool.

Install JDK version 8 (later versions may lead to some issues, e.g., Qt doesn't accept Android SDK). I picked OpenJDK having executed apt install openjdk-8-jre openjdk-8-jdk.

Install Yasm (FFmpeg dependency). I got it from packages: apt install yasm.

Install Android Studio to get Android SDK https://developer.android.com/studio/index.html. Handling some Android stuff without Android Studio is painful.

Download and unpack Android NDK https://developer.android.com/ndk/downloads.

You also have to add the Android NDK and SDK paths in Qt Creator at Tools > Options > Devices > Android. If Qt Creator doesn't accept your SDK then try to download SDK tools using the link from sdk_tools_url from here https://github.com/qt-creator/qt-creator/blob/master/share/qtcreator/android/sdk_definitions.json and unpack into your SDK. After everything is green click Update Installed inside SDK Manager tab to accept licenses.

Create environment variables OPENCV_SRC_DIR, FFMPEG_SRC_DIR. Consider them to be the paths to future directories opencv and FFmpeg in a directory where you are going to execute the build scripts, e.g., directly in this repository. In order to register environment variables in my system I put these lines

export OPENCV_SRC_DIR=$HOME/opencv-with-ffmpeg-on-qt-for-android/opencv
export FFMPEG_SRC_DIR=$HOME/opencv-with-ffmpeg-on-qt-for-android/FFmpeg

to ~/.profile and relogin.

Now edit NDK_PATH along with ANDROID_SDK_ROOT inside build.sh and run this script to build FFmpeg 4.2.1 and OpenCV 4.1.2 for x86 and armeabi-v7a using Clang. Sources are downloaded automatically.

Running the sample application

Open sample/sample.pro in Qt Creator. Change ARCHITECTURE to the corresponding architecture for your current build. Note that this project uses your previously registered environment variable OPENCV_SRC_DIR in order to obtain libraries. Build and run. Device management is left on you. In case of success the application generates a sample video.