In the iCubie Camera app, we used FFmpeg to encode video in MPEG-4 part-12 format only for Android devices of of API 18 (4.3 Jelly Bean) or older. FFmpeg is linked in the app as four shared NDK libraries (ibavcodec-55.so, libavformat-55.so, libavutil-52.so and libswresample-0.so).

We mainly followed the instructions by roman10 to compile FFmpeg source code package for Android platform. Below are steps we actually took.

It is assumed that you have already had Android NDK toolchain installed and have the knowledge building NDK library for Android applications. In the following paragraphs, NDK_INSTALLATION refers to your NDK installation. In our case, it is $HOME/android-ndk-r9d on Mac OS X machine.

1. Download the latest FFmpeg source code package from the official FFmpeg web site.

   At the time of this writing, the FFmpeg version is 2.2.3.

   cd NDK_INSTALLATION/sources
   git clone git://source.ffmpeg.org/ffmpeg.git ffmpeg
   

2. Edit the file NDK_INSTALLATION/sources/ffmpeg/configure.

   Replace the following lines

   LIBNAME_WITH_MAJOR='$(SLIBNAME).$(LIBMAJOR)'
   LIB_INSTALL_EXTRA_CMD='$$(RANLIB) "$(LIBDIR)/$(LIBNAME)"'
   SLIB_INSTALL_NAME='$(SLIBNAME_WITH_VERSION)'
   SLIB_INSTALL_LINKS='$(SLIBNAME_WITH_MAJOR) $(SLIBNAME)'
   

   with

   SLIBNAME_WITH_MAJOR='$(SLIBPREF)$(FULLNAME)-$(LIBMAJOR)$(SLIBSUF)'
   LIB_INSTALL_EXTRA_CMD='$$(RANLIB) "$(LIBDIR)/$(LIBNAME)"'
   SLIB_INSTALL_NAME='$(SLIBNAME_WITH_MAJOR)'
   SLIB_INSTALL_LINKS='$(SLIBNAME)'
   

3. Decide which FFmpeg components you will need. In our case, all we needed were mpeg4 video encoder and mp4 muxer so we disabled everything else. Doing so can significantly reduce the footprint of the FFmpeg libraries. In our case the sizes are:

   -rwxr-xr-x  1 pico pico  515548 Jun 11 11:50 libavcodec-55.so
   -rwxr-xr-x  1 pico pico  214912 Jun 11 11:50 libavformat-55.so
   -rwxr-xr-x  1 pico pico  177704 Jun 11 11:50 libavutil-52.so
   -rwxr-xr-x  1 pico pico   79260 Jun 11 11:50 libswresample-0.so
   

4. Create the file NDK_INSTALLATION/sources/ffmpeg/build_android.sh with the following lines as the build shell script. Enable whatever components you will need.

   #!/bin/bash
   
   NDK=$HOME/android-ndk-r9d
   SYSROOT=$NDK/platforms/android-12/arch-arm/
   TOOLCHAIN=$NDK/toolchains/arm-linux-androideabi-4.8/prebuilt/darwin-x86_64
   
   function build_one
   {
   ./configure \
       --prefix=$PREFIX \
       --enable-small \
       --enable-shared \
       --disable-static \
       --disable-encoders \
       --disable-decoders \
       --disable-muxers \
       --disable-demuxers \
       --disable-parsers \
       --disable-bsfs \
       --disable-protocols \
       --disable-filters \
       --enable-encoder=mpeg4 \
       --enable-muxer=mp4 \
       --enable-protocol=file \
       --disable-doc \
       --disable-ffmpeg \
       --disable-ffplay \
       --disable-ffprobe \
       --disable-ffserver \
       --disable-avdevice \
       --disable-doc \
       --disable-symver \
       --cross-prefix=$TOOLCHAIN/bin/arm-linux-androideabi- \
       --target-os=linux \
       --arch=arm \
       --enable-cross-compile \
       --sysroot=$SYSROOT \
       --extra-cflags="-Os -fpic $ADDI_CFLAGS" \
       --extra-ldflags="$ADDI_LDFLAGS" \
       $ADDITIONAL_CONFIGURE_FLAG
   
   make clean
   make
   make install
   }
   
   CPU=armv7-a
   PREFIX=$(pwd)/android/$CPU 
   ADDI_CFLAGS="-marm -march=$CPU -mfpu=neon"
   
   build_one
   

   We only targeted the armv7-a CPU architecture as it is widely supported by most Android devices out there. Tailor your own.

   Make sure you set up environment variables $NDK, $SYSROOT and $TOOLCHAIN accordingly.

   Also make sure your build shell script can be executed.

   chmod +x NDK_INSTALLATION/sources/ffmpeg/build_android.sh
   

5. Build FFmpeg

   cd NDK_INSTALLATION/sources/ffmpeg/
   ./build_android.sh
   

   It may take a while, really. Once done, the compiled libraries and needed include files are placed in the folder NDK_INSTALLATION/sources/ffmpeg/android.

6. Make all the compiled FFmpeg libraries available to your NDK project.

   Create the file NDK_INSTALLATION/sources/ffmpeg/android/Android.mk with the following lines.

   LOCAL_PATH:= $(call my-dir)
   
   include $(CLEAR_VARS)
   
   LOCAL_MODULE:= libavcodec
   LOCAL_SRC_FILES:= lib/libavcodec-55.so
   LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/include
   include $(PREBUILT_SHARED_LIBRARY)
   
   include $(CLEAR_VARS)
   
   LOCAL_MODULE:= libavformat
   LOCAL_SRC_FILES:= lib/libavformat-55.so
   LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/include
   include $(PREBUILT_SHARED_LIBRARY)
   
   include $(CLEAR_VARS)
   LOCAL_MODULE:= libswscale
   LOCAL_SRC_FILES:= lib/libswscale-2.so
   LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/include
   include $(PREBUILT_SHARED_LIBRARY)
   
   include $(CLEAR_VARS)
   
   LOCAL_MODULE:= libavutil
   LOCAL_SRC_FILES:= lib/libavutil-52.so
   LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/include
   include $(PREBUILT_SHARED_LIBRARY)
   
   include $(CLEAR_VARS)
   
   LOCAL_MODULE:= libavfilter
   LOCAL_SRC_FILES:= lib/libavfilter-4.so
   LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/include
   include $(PREBUILT_SHARED_LIBRARY)
   
   include $(CLEAR_VARS)
   
   LOCAL_MODULE:= libswresample
   LOCAL_SRC_FILES:= lib/libswresample-0.so
   LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/include
   include $(PREBUILT_SHARED_LIBRARY)
   

7. Import FFmpeg libraries into your NDK build project.

   Append the following lines to your Android project's NDK makefile jni/Android.mk.

   $(call import-module,ffmpeg/android/armv7-a)
   

   Here is an example how we built our videoencoder NDK library using the imported FFmpeg library modules.

   LOCAL_PATH := $(call my-dir)
   
   include $(CLEAR_VARS)
   
   LOCAL_MODULE    := videoencoder
   LOCAL_SRC_FILES := videoencoder.c
   
   LOCAL_LDLIBS := -llog
   
   LOCAL_SHARED_LIBRARIES := libavformat libavcodec libavutil libswresample
   
   include $(BUILD_SHARED_LIBRARY)
   
   $(call import-module,ffmpeg/android/armv7-a)
   

8. Load the NDK libraries in your Java class that calls native NDK functions.

   Here is an example of our VideoEncoderFFmpeg class.

   public class VideoEncoderFFmpeg {
       ...
   
       /* load up shared libraries */
       static {
           System.loadLibrary("avutil-52");
           System.loadLibrary("avcodec-55");
           System.loadLibrary("avformat-55");
           System.loadLibrary("swresample-0");
           System.loadLibrary("videoencoder");
       }
   }
   

That is all it takes. Have fun building FFmpeg and NDK. Let us know if you need help from us. You can leave us a message at the bottom of this page.