1 修改FFmpeg的configure

下载FFmpeg源代码之后，首先需要对源代码中的configure文件进行修改。由于编译出来的动态库文件名的版本号在.so之后(例如libavcodec.so.5.100.1)，而Android平台不能识别这样文件名，所以需要修改这种文件名。在configure文件中找到下面几行代码：

SLIBNAME_WITH_MAJOR='$(SLIBNAME).$(LIBMAJOR)'

LIB_INSTALL_EXTRA_CMD='$$(RANLIB)"$(LIBDIR)/$(LIBNAME)"'

SLIB_INSTALL_NAME='$(SLIBNAME_WITH_VERSION)'

SLIB_INSTALL_LINKS='$(SLIBNAME_WITH_MAJOR)$(SLIBNAME)'

替换为下面内容即可：

SLIBNAME_WITH_MAJOR='$(SLIBPREF)$(FULLNAME)-$(LIBMAJOR)$(SLIBSUF)'

LIB_INSTALL_EXTRA_CMD='$$(RANLIB)"$(LIBDIR)/$(LIBNAME)"'

SLIB_INSTALL_NAME='$(SLIBNAME_WITH_MAJOR)'

SLIB_INSTALL_LINKS='$(SLIBNAME)'

2 编库

软解库

编译多个库的脚本如下，生成libavcodec-57.so libavdevice.so libavformat-57.so libavutil.so libswscale-4.so libavcodec.so libavfilter-6.so libavformat.so libswresample-2.so libswscale.so libavdevice-57.so libavfilter.so libavutil-55.so libswresample.so等库：

#! /bin/sh

NDK=../../NDK/android-ndk-r12b

SYSROOT=$NDK/platforms/android-9/arch-arm/

TOOLCHAIN=$NDK/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64

CPU=arm

PREFIX=../test

ADDI_CFLAGS="-marm"

build_one()

{

./configure --prefix=$PREFIX --enable-shared --disable-static --disable-doc --disable-ffserver --enable-cross-compile --cross-prefix=$TOOLCHAIN/bin/arm-linux-androideabi- --target-os=linux --arch=arm --sysroot=$SYSROOT --extra-cflags="-Os -fpic $ADDI_CFLAGS" --extra-ldflags="$ADDI_LDFLAGS" $ADDITIONAL_CONFIGURE_FLAG

make clean

make

make install

}

build_one

将编译的多个库整合为一个ffmpeg.so库的编译脚本如下，注意：当整合为一个动态库时，要先编译出.a的静态库(修改./configure后的参数--enable-shared --disable-static为--disable-shared --enable-static)，再将各静态库合并为一个动态库：

#! /bin/sh

NDK=../../NDK/android-ndk-r12b

SYSROOT=$NDK/platforms/android-9/arch-arm/

TOOLCHAIN=$NDK/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64

CPU=arm

PREFIX=../test

ADDI_CFLAGS="-marm"

export PREBUILT=$NDK/toolchains/arm-linux-androideabi-4.9/prebuilt

export PLATFORM=$NDK/platforms/android-14/arch-arm

build_one()

{

./configure --prefix=$PREFIX --disable-shared --enable-static --disable-doc --disable-ffserver --enable-cross-compile --cross-prefix=$TOOLCHAIN/bin/arm-linux-androideabi- --target-os=linux --arch=arm --sysroot=$SYSROOT --extra-cflags="-Os -fpic $ADDI_CFLAGS" --extra-ldflags="$ADDI_LDFLAGS" $ADDITIONAL_CONFIGURE_FLAG

make clean

make

make install

}

build_one

$PREBUILT/linux-x86_64/bin/arm-linux-androideabi-ld -rpath-link=$PLATFORM/usr/lib -L$PLATFORM/usr/lib -L$PREFIX/lib -soname libffmpeg.so -shared -nostdlib -Bsymbolic --whole-archive --no-undefined -o $PREFIX/libffmpeg.so libavcodec/libavcodec.a libavfilter/libavfilter.a libswresample/libswresample.a libavformat/libavformat.a libavutil/libavutil.a libswscale/libswscale.a libavdevice/libavdevice.a -lc -lm -lz -ldl -llog --dynamic-linker=/system/bin/linker $PREBUILT/linux-x86_64/lib/gcc/arm-linux-androideabi/4.9.x/libgcc.a

最初编译脚本如下：

#! /bin/bash

NDK=../../NDK/android-ndk-r12b

SYSROOT=$NDK/platforms/android-9/arch-arm/

TOOLCHAIN=$NDK/toolchains/arm-linux-androideabi-4.8/prebuilt/linux-x86_64

CPU=arm

PREFIX=../test

ADDI_CFLAGS="-marm"

function build_one

{

./configure \

--prefix=$PREFIX \

--enable-shared \

--disable-static \

--disable-doc \

--disable-ffmpeg \

--disable-ffplay \

--disable-ffprobe \

--disable-ffserver \

--disable-doc \

--disable-symver \

--enable-small \

--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

}

build_one

遇到的问题：

0 Cygwin编不出，要在Linux环境下编译

1 执行xxx.sh时提示Permission denied

原因：没有执行权限

解决：执行chmod a+x xxx.sh命令，赋予执行权限

2 --prefix=../test command not found, --enable-shared command not found, --disable-staticcommand not found......

解决：将./configure后的\换行删除，该命令并成一行

3 arm-linux-androideabi-gcc is unable to create an executable file.

原因：TOOLCHAIN路径错误

解决：将arm-linux-androideabi-4.8改为arm-linux-androideabi-4.9，android-ndk-r12b下没有4.8路径

硬解库

编译脚本如下：

#!/bin/bash

export NDK=../../NDK/android-ndk-r12b

echo "Fetching Android system headers"

git clone --depth=1 --branch gingerbread-release git://github.com/CyanogenMod/android_frameworks_base.git ../android-source/frameworks/base

git clone --depth=1 --branch gingerbread-release git://github.com/CyanogenMod/android_system_core.git ../android-source/system/core

echo "Fetching Android libraries for linking"

# Libraries from any froyo/gingerbread device/emulator should work

# fine, since the symbols used should be available on most of them.

if [ ! -d "../android-libs" ]; then

if [ ! -f "../update-cm-7.0.3-N1-signed.zip" ]; then

wget https://jaist.dl.sourceforge.net/project/nexusoneandroid/update-cm-7.0.3-N1-signed.zip -P../

fi

unzip ../update-cm-7.0.3-N1-signed.zip system/lib/* -d../

mv ../system/lib ../android-libs

rmdir ../system

fi

SYSROOT=$NDK/platforms/android-9/arch-arm

# Expand the prebuilt/* path into the correct one

TOOLCHAIN=`echo $NDK/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64`

export PATH=$TOOLCHAIN/bin:$PATH

ANDROID_SOURCE=../android-source

ANDROID_LIBS=../android-libs

ABI="armeabi-v7a"

rm -rf ../build/stagefright

mkdir -p ../build/stagefright

DEST=../build/stagefright

FLAGS="--target-os=linux --cross-prefix=arm-linux-androideabi- --arch=arm --cpu=armv7-a"

FLAGS="$FLAGS --sysroot=$SYSROOT"

FLAGS="$FLAGS --disable-avdevice --disable-decoder=h264 --disable-decoder=h264_vdpau --enable-decoder=libstagefright_h264"

EXTRA_CFLAGS="-I$ANDROID_SOURCE/frameworks/base/include -I$ANDROID_SOURCE/system/core/include"

EXTRA_CFLAGS="$EXTRA_CFLAGS -I$ANDROID_SOURCE/frameworks/base/media/libstagefright"

EXTRA_CFLAGS="$EXTRA_CFLAGS -I$ANDROID_SOURCE/frameworks/base/include/media/stagefright/openmax"

EXTRA_CFLAGS="$EXTRA_CFLAGS -I$NDK/sources/cxx-stl/gnu-libstdc++/4.9/include -I$NDK/sources/cxx-stl/gnu-libstdc++/4.9/libs/$ABI/include"

EXTRA_CFLAGS="$EXTRA_CFLAGS -march=armv7-a -mfloat-abi=softfp -mfpu=neon"

EXTRA_LDFLAGS="-Wl,--fix-cortex-a8 -L$ANDROID_LIBS -Wl,-rpath-link,$ANDROID_LIBS -L$NDK/sources/cxx-stl/gnu-libstdc++/4.9/libs/$ABI -lstagefright -lstdc++ -lutils -lbinder -lgnustl_static -lgnustl_shared"

#EXTRA_LDFLAGS="$EXTRA_LDFLAGS -lcutils -ldl -lstlport -lc -lm -lz -ldl -llog -lstdc++ -lstagefright -lbinder -lstlport -lstdc++ -lstl"

EXTRA_CXXFLAGS="-Wno-multichar -fno-exceptions -fno-rtti"

DEST="$DEST/$ABI"

FLAGS="$FLAGS --prefix=$DEST"

mkdir -p $DEST

echo $FLAGS --extra-cflags="$EXTRA_CFLAGS" --extra-ldflags="$EXTRA_LDFLAGS" --extra-cxxflags="$EXTRA_CXXFLAGS" > $DEST/info.txt

./configure $FLAGS --extra-cflags="$EXTRA_CFLAGS" --extra-ldflags="$EXTRA_LDFLAGS" --extra-cxxflags="$EXTRA_CXXFLAGS" | tee $DEST/configuration.txt

[ $PIPESTATUS == 0 ] || exit 1

make clean

make -j4 || exit 1

make install

export PREBUILT=$NDK/toolchains/arm-linux-androideabi-4.9/prebuilt

export PLATFORM=$NDK/platforms/android-14/arch-arm

PREFIX=../build/stagefright/armeabi-v7a

#合并包

$PREBUILT/linux-x86_64/bin/arm-linux-androideabi-ld -rpath-link=$PLATFORM/usr/lib -L$PLATFORM/usr/lib -L$PREFIX/lib -soname libffmpeg.so -shared -nostdlib -Bsymbolic --whole-archive --no-undefined -o $PREFIX/libffmpeg.so libavcodec/libavcodec.a libavfilter/libavfilter.a libswresample/libswresample.a libavformat/libavformat.a libavutil/libavutil.a libswscale/libswscale.a -lc -lm -lz -ldl -llog --dynamic-linker=/system/bin/linker $PREBUILT/linux-x86_64/lib/gcc/arm-linux-androideabi/4.9.x/libgcc.a