如何将ffmpeg移植到Android平台

编译带h264编码器的ffmepg库在Android4.6平台上运行，主要步骤如下:

1、下载ffmpeg源码(我使用的2.7版本)

2、下载h264编码器

3、编译h264编码器静态库(build_h264.sh)

export NDK=/home/juhaowangluo/ndk/android-ndk-r10dexport PREBUILT=$NDK/toolchains/arm-linux-androideabi-4.6/prebuiltexport PLATFORM=$NDK/platforms/android-19/arch-armexport PREFIX=/home/juhaowangluo/LiuCongkuan/ffmpeg/Android_ndk/android-x264./configure --prefix=$PREFIX --cross-prefix=/home/juhaowangluo/ndk/android-ndk-r10d/toolchains/arm-linux-androideabi-4.6/prebuilt/linux-x86_64/bin/arm-linux-androideabi- --sysroot=/home/juhaowangluo/ndk/android-ndk-r10d/platforms/android-19/arch-arm --enable-static --enable-pic --disable-asm --disable-cli --host=arm-linux

编译成功后会在ffmpeg/Android_ndk/android-x264/lib目录中出现一个libx264.a文件

4、编译ffmpeg库(build_ffmepg.sh)

     这一步问题最多，大家遇到了慢慢解决，我只把我遇到问题列一下。

     网上编译脚本很多，但都很复杂，这个相对来说简单点(我对make file脚本不熟)。

#!/bin/shNDK="/home/juhaowangluo/ndk/android-ndk-r10d"PREBUILT="/home/juhaowangluo/ndk/android-ndk-r10d/toolchains/arm-linux-androideabi-4.6/prebuilt"PLATFORM="/home/juhaowangluo/ndk/android-ndk-r10d/platforms/android-19/arch-arm"PREFIX="/home/juhaowangluo/LiuCongkuan/ffmpeg/Android_ndk/android-x264"build_one(){./configure --target-os=linux --prefix=/home/juhaowangluo/LiuCongkuan/ffmpeg/Android_ndk/android-x264 \--enable-cross-compile \--enable-runtime-cpudetect \--disable-asm \--arch=arm \--cc=/home/juhaowangluo/ndk/android-ndk-r10d/toolchains/arm-linux-androideabi-4.6/prebuilt/linux-x86_64/bin/arm-linux-androideabi-gcc \--cross-prefix=/home/juhaowangluo/ndk/android-ndk-r10d/toolchains/arm-linux-androideabi-4.6/prebuilt/linux-x86_64/bin/arm-linux-androideabi- \--disable-stripping \--nm=/home/juhaowangluo/ndk/android-ndk-r10d/toolchains/arm-linux-androideabi-4.6/prebuilt/linux-x86_64/bin/arm-linux-androideabi-nm \--sysroot=/home/juhaowangluo/ndk/android-ndk-r10d/platforms/android-19/arch-arm \--enable-nonfree \--enable-version3 \--disable-everything \--enable-gpl \--disable-doc \--enable-avresample \--enable-demuxers \--enable-muxers \--disable-ffplay \--disable-ffserver \--disable-ffmpeg \--disable-ffprobe \--disable-devices \--disable-avdevice \--enable-encoders \--enable-decoders \--enable-libx264 \--enable-encoder=libx264 \--enable-decoder=h264 \--enable-protocols \--enable-hwaccels \--enable-zlib \--enable-decoder=flv \--enable-encoder=flv \--enable-decoder=rawvideo \--enable-decoder=h263 \--enable-parser=h263 \--enable-demuxer=h263 \--extra-cflags="-I/home/juhaowangluo/LiuCongkuan/ffmpeg/Android_ndk/android-x264/include -fPIC -DANDROID -D__thumb__ -mthumb -Wfatal-errors -Wno-deprecated -mfloat-abi=softfp -mfpu=vfpv3-d16 -marm -march=armv7-a" \--extra-ldflags="-L/home/juhaowangluo/LiuCongkuan/ffmpeg/Android_ndk/android-x264/lib"make -j4 install/home/juhaowangluo/ndk/android-ndk-r10d/toolchains/arm-linux-androideabi-4.6/prebuilt/linux-x86_64/bin/arm-linux-androideabi-ar d libavcodec/libavcodec.a inverse.o/home/juhaowangluo/ndk/android-ndk-r10d/toolchains/arm-linux-androideabi-4.6/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  -z noexecstack -Bsymbolic --whole-archive --no-undefined -o ${PREFIX}/libffmpeg.so libavcodec/libavcodec.a libavfilter/libavfilter.a libavresample/libavresample.a libavformat/libavformat.a libavutil/libavutil.a libswscale/libswscale.a libswresample/libswresample.a -lc -lm -lz -ldl -llog -lx264 --dynamic-linker=/system/bin/linker ${PREBUILT}/linux-x86_64/lib/gcc/arm-linux-androideabi/4.6/libgcc.a}build_one

编译成功后会在Android_ndk\android-x264下面生成一个libffmpeg.so文件，到此带h264编码的ffmepg库编译完成。

这次编译过程遇到问题，这里也列一下，整改过程中h264编译很顺畅，一次通过。主要说下ffmepg编码的问题:

1、链接h264库

--enable-libx264 \
--enable-encoder=libx264 \
--enable-decoder=h264 \

设置h264库和h文件的路径:

--extra-cflags="-I/home/juhaowangluo/LiuCongkuan/ffmpeg/Android_ndk/android-x264/include“

--extra-ldflags="-L/home/juhaowangluo/LiuCongkuan/ffmpeg/Android_ndk/android-x264/lib"

2、错误1: 报h263链接错误

解决方法，如下

--enable-decoder=rawvideo \
--enable-decoder=h263 \
--enable-parser=h263 \
--enable-demuxer=h263 \

3、错误2: h263编译链接错误通过上面的方法解决后，又出现”opusdec.c  error: undefined reference to 'swr_is_initialized'“的类似链接错误

解决方法，如下

加入libswresample.a链接库