QtMultimedia on Android

Overview

With the introduction of FFmpeg in QtMultimedia for Android starting from version 6.7, developers now have a robust option for handling multimedia tasks. This shift is significant as the MediaCodec-based backend is deprecated from Qt 6.8 and is scheduled for removal in Qt 7.0. Therefore, it is highly recommended to transition to FFmpeg for future-proofing your multimedia applications on Android.

This guide will walk you through the steps to build QtMultimedia with FFmpeg on Android.

Building QtMultimedia with FFmpeg

Before we start building FFmpeg there are some prerequisites that should be taken into account.

For windows

1. Install Msys2 from msys2.org
2. Complete the steps and open Msys2
3. Update package databases pacman -Syu
4. Update rest of base packages pacman -Su
5. Install Mingw-w64: pacman -S --needed base-devel mingw-w64-x86_64-toolchain
6. Install CMake  : pacman -S mingw-w64-x86_64-cmake
7. Install Ninja : pacman -S mingw-w64-x86_64-ninja
8. Make sure to launch MSYS2 MinGW 64-bit

Then follow the below instructions make sure you run the below on MSYS2 MinGW 64-bit

1- Clone the FFmpeg Repository

Start by cloning the official FFmpeg repository:

git clone https://github.com/FFmpeg/FFmpeg.git

2- Create a Build Script

Copy the following script into a file named build-ffmpeg-android.sh. This script will be used to build FFmpeg for Android:

#!/bin/bash

helpFunction() {
    echo "Usage: ./build-ffmpeg-android.sh --arch=ARCH --install-path=PATH"
    echo -e "\t--target-arch     Select target architecture [aarch64, armv7, x86, x86_64]"
    echo -e "\t--host-arch    Select the host machine architecture [linux-x86_64, darwin-x86_64, windows-x86_64]"
    echo -e "\t--install-path    Install in PATH used in make install, full path please"
    exit 1
}

# Parse command-line options
for opt in "$@"; do
    case "$opt" in
        --target-arch=*)
            ARCH="${opt#*=}"
        ;;
        --install-path=*)
            INSTALL_PATH="${opt#*=}"
        ;;
	--host-arch=*)
            HOST_ARCH="${opt#*=}"
        ;;

        *)
            helpFunction
        ;;
    esac
done

# Check for empty parameters
if [ -z "$ARCH" ] || [ -z "$HOST_ARCH" ] || [ -z "$INSTALL_PATH" ]; then
    echo "Some or all of the parameters are empty"
    helpFunction
fi

# Check for required environment variables
if [ -z "$ANDROID_NDK_ROOT" ] || [ -z "$FFMPEG_LIBRARY_PATH" ]; then
    echo "Please set ANDROID_NDK_ROOT, HOST_ARCH, and FFMPEG_LIBRARY_PATH."
    exit 1
fi

# Setup architecture-specific variables
case "$ARCH" in
    aarch64)
        TOOLCHAIN_ARCH="aarch64-linux-android"
        CPU="armv8-a"
    ;;
    armv7)
        TOOLCHAIN_ARCH="armv7a-linux-androideabi"
        CPU="armv7-a"
    ;;
    x86)
        TOOLCHAIN_ARCH="i686-linux-android"
        CPU="i686"
    ;;
    x86_64)
        TOOLCHAIN_ARCH="x86_64-linux-android"
        CPU="x86-64"
    ;;
    *)
        echo "Invalid architecture: $ARCH"
        helpFunction
    ;;
esac

ANDROID_OPTIONS="
--target-os=android
--arch=${ARCH}
--cpu=${CPU}
--enable-cross-compile
--enable-jni
--enable-mediacodec
--enable-pthreads
--disable-indev=android_camera
--sysroot=${ANDROID_NDK_ROOT}/toolchains/llvm/prebuilt/${HOST_ARCH}/sysroot
--sysinclude=${ANDROID_NDK_ROOT}/toolchains/llvm/prebuilt/${HOST_ARCH}/sysroot/usr/include/
--cc=${ANDROID_NDK_ROOT}/toolchains/llvm/prebuilt/${HOST_ARCH}/bin/${TOOLCHAIN_ARCH}24-clang
--cxx=${ANDROID_NDK_ROOT}/toolchains/llvm/prebuilt/${HOST_ARCH}/bin/${TOOLCHAIN_ARCH}24-clang++
--disable-autodetect
--enable-neon
--disable-asm
"

export LDFLAGS="-L${ANDROID_NDK_ROOT}/toolchains/llvm/prebuilt/${HOST_ARCH}/sysroot/usr/lib/${TOOLCHAIN_ARCH} -L${ANDROID_NDK_ROOT}/toolchains/llvm/prebuilt/${HOST_ARCH}/sysroot/usr/lib/${TOOLCHAIN_ARCH}/24 -lm -ldl -llog"
export CFLAGS="-O3 -Wl,exclude-libs,libgcc.a,libunwind.a"

COMMON_OPTIONS="
--prefix=${INSTALL_PATH}
--enable-static
--disable-shared
--host-os=${HOST_ARCH}
--install-name-dir=${INSTALL_PATH}
--disable-logging
--disable-debug
--disable-programs
--enable-pic
"

pushd ${FFMPEG_LIBRARY_PATH}
make clean
make distclean

echo "./configure ${COMMON_OPTIONS} ${ANDROID_OPTIONS}"
./configure ${COMMON_OPTIONS} ${ANDROID_OPTIONS}

sed -i "s/-fPIE/-fPIC/" ffbuild/config.mak
sed -i "s/-pie/-pic/" ffbuild/config.mak

make -j8 install
popd

Note: When building FFmpeg with openssl dependencies. Make sure the below environment variables are set

export ANDROID_OPENSSL_INCLUDE=openssl_include_location 
export ANDROID_OPENSSL_LIBS=openssl_libs_location

Please add the flags below during FFmpeg configuration (Line 104)

--enable-openssl --extra-cflags=-I${ANDROID_OPENSSL_INCLUDE} --extra-ldflags=-L${ANDROID_OPENSSL_LIBS}

3- Set Environment Variables

Set the environment variables as they are needed to build ffmpeg

export ANDROID_NDK_ROOT=android_ndk_location (i.e ~/Library/Android/sdk/ndk/25.1.8937393) (in windows paths are like =/c/Users/usr/AppData/Local/Android/Sdk/ndk/25.1.8937393)
export FFMPEG_LIBRARY_PATH=cloned_ffmpeg_location (i.e ~/Workspace/Ffmpeg/ffmpeg-android/ffmpeg)

4- Build FFmpeg for Android

Run the build script to build FFmpeg for the specified architecture:

sh build-ffmpeg-android.sh --target-arch=aarch64 --host-arch=darwin-x86_64 (for windows: windows-x86_64)--install-path=desired_install_path

5- Configure and Build QtMultimedia

After generating the FFmpeg libraries, configure QtMultimedia with the appropriate flags:

cd /path/to/qt/source
./configure .... 
-D FFMPEG_DIR:PATH=ffmpeg_built_libs_path

If openssl is enabled during FFmpeg configuration make sure you add to the above command

-D OPENSSL_INCLUDE_DIR=openssl_include_folder_path

For more information on how to build qt for Android check Qt from source for Android