为Android编译FFMpeg

• 新建：build_android.sh

#!/bin/bash

# NDK途径 
export NDK=/Users/lucius/Library/Android/sdk/ndk-bundle 
# NDK东西链 
export PREBUILT=$NDK/toolchains/arm-linux-androideabi-4.9/prebuilt 
# 编译平台 
export PLATFORM=$NDK/platforms/android-14/arch-arm 
# 编译功效输入途径 
export PREFIX=/Users/lucius/development/workspaces/target/ffmpeg/optimized 
# 设置编译功效运转平台 
CPU=arm 
ARCH=arm # -marm -mthumb gcc编译器参数 
# marm功能优于mthumb百分之10到15，mthumb兼容性更好，可以调试用marm，发版用mthumb ADDI_CFLAGS="-marm" 
# 开端编译设置 
./configure / 
# 设置输入途径 
--prefix=$PREFIX / 
# 设置编纂功效目的运转零碎 
--target-os=android / 
# 设置编译效果cpu架构 
--arch=$ARCH / 
# 设置编译效果运转平台 
--sysroot=$PLATFORM / 
# 交织编译东西链 
--cross-prefix=$PREBUILT/darwin-x86_64/bin/arm-linux-androideabi- / 
# gcc编译参数 
--extra-ldflags="$ADDI_LDFLAGS" / 
# 从编译参数 
--extra-cflags="-Os -fpic $ADDI_CFLAGS" / 
# 紧缩编译 --enable-small / 
# 运用GPL，！！！GPL！！！ 
--enable-gpl / 
# 多线程编解码 
--enable-pthreads / 
# 禁用文档 --disable-doc / 
# 禁用ffmpeg下令，android会有本身的出口 
--disable-ffmpeg / 
# 禁用ffplay下令，android不须要 
--disable-ffplay / 
# 禁用ffprobe下令，android不须要 
--disable-ffprobe / 
# 禁用ffserver下令，android不须要 
--disable-ffserver / 
# 禁用network，android不须要 -
-disable-network / 
# 禁用ffplay下令，android不须要 
--disable-shared / 
# 禁用一切编解码器，今后再按照需求增加编解码器 
--disable-encoders / 
--disable-decoders / 
#编解码传输和谈 
--enable-protocols / 
# 滤镜处置 
--enable-filters / 
# 开启mp4音视频相干的编解码器 
--enable-decoder=mpeg4 / 
--enable-decoder=h264 / 
--enable-decoder=mp3 / 
--enable-decoder=aac / 
--enable-encoder=mpeg4 / 
--enable-encoder=libx264 / 
--enable-encoder=aac / 
# 未知选项 
$ADDITIONAL_CONFIGURE_FLAG 
# 清空前次编纂 
make clean 
# 开端四核编译 -j2暗示双核 
make -j4 
# 输入编译效果到指定目次 
make install 
# 以下脚本暗示将分离的so库合并成一个libffmpeg.so,详细指令寄义待研究 
$PREBUILT/darwin-x86_64/bin/arm-linux-androideabi-ld / 
-rpath-link=$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 / 
libavformat/libavformat.a / 
libavutil/libavutil.a / 
libavfilter/libavfilter.a / 
libavdevice/libavdevice.a / 
libpostproc/libpostproc.a / 
libswresample/libswresample.a / 
libswscale/libswscale.a / 
-lc 
-lm 
-lz 
-ldl 
-llog 
--dynamic-linker=/system/bin/linker / 
$PREBUILT/darwin-x86_64/lib/gcc/arm-linux-androideabi/4.9.x/libgcc.a 
$PREBUILT/darwin-x86_64/bin/arm-linux-androideabi-strip 
$PREFIX/libffmpeg.so  

• 需要修改下 ffmpeg/configure，使导出的so库文件名称符合NDK的规范

将

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)'

修改为：

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

• 编译所有的平台：
  ffmpeg + x264编译脚本

• 附：编译fdk-aac脚本：

#!/bin/sh

#!/bin/sh

CPU=armeabi-v7a
PREFIX=$(pwd)/output/$CPU
NDK_HOME=/Users/eraise/Library/Android/ndk
ANDROID_API=android-23
SYSROOT=$NDK_HOME/platforms/$ANDROID_API/arch-arm
ANDROID_BIN=$NDK_HOME/toolchains/arm-linux-androideabi-4.9/prebuilt/darwin-x86_64/bin/
CROSS_COMPILE=${ANDROID_BIN}arm-linux-androideabi-
ARM_INC=$SYSROOT/usr/include 
ARM_LIB=$SYSROOT/usr/lib
LDFLAGS=" -nostdlib -Bdynamic -Wl,--whole-archive -Wl,--no-undefined -Wl,-z,noexecstack  -Wl,-z,nocopyreloc -Wl,-soname,/system/lib/libz.so -Wl,-rpath-link=$ARM_LIB,-dynamic-linker=/system/bin/linker -L$NDK_HOME/sources/cxx-stl/gnu-libstdc++/4.9/libs/$CPU -L$NDK_HOME/toolchains/arm-linux-androideabi-4.9/prebuilt/darwin-x86_64/arm-linux-androideabi/lib -L$ARM_LIB  -lc -lgcc -lm -ldl  "
FLAGS="--host=arm-androideabi-linux --enable-static --disable-shared"
export CXX="${CROSS_COMPILE}g++ --sysroot=${SYSROOT}"
export LDFLAGS="$LDFLAGS"
export CC="${CROSS_COMPILE}gcc --sysroot=${SYSROOT}"

./configure $FLAGS \
--prefix=$PREFIX

make clean 
make -j4
make install

需要注意，脚本中的./configure 如果分行写，"\"右边不能再有空格，否则报configure: error: /bin/sh build/config.sub failed

• 错误:

error: undefined reference to 'av_register_all()'
error: undefined reference to 'avcodec_register_all()'
error: undefined reference to 'avformat_network_init()'

解决方案是把 ffmpeg 的头文件用extern "C" 包起来
(方案来源：贝壳博客):

extern "C" {

#include <libavformat/avformat.h>
#include <libavutil/imgutils.h>

build_android.sh来源