模拟器与真机下ffmpeg的编译方法（总结版）
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如果不了解什么是ffmepg，请移步http://ffmpeg.org 先了解下：）
编译ffmepg模拟器版本：
1. 到https://github.com/gabriel/ffmpeg-iphone-build下载ffmpeg-iphone-build
2.先将gas-preprocessor.pl拷贝到/usr/sbin/目录中。
3.到ffmpeg官网上下载ffmpeg源码
4.在终端下定位到ffmpeg的目录运行
./configure --disable-doc --disable-ffmpeg --disable-ffplay --disable-ffserver --disable-avfilter --disable-debug --disable-encoders --enable-cross-compile --disable-decoders --disable-armv5te --enable-decoder=h264 --enable-pic --cc=/Developer/Platforms/iPhoneSimulator.platform/Developer/usr/bin/gcc --as='gas-preprocessor/gas-preprocessor.pl /Developer/Platforms/iPhoneSimulator.platform/Developer/usr/bin/gcc' --extra-ldflags=-L/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator4.3.sdk/usr/lib/system --sysroot=/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator4.3.sdk --target-os=darwin --arch=i386 --cpu=i386 --extra-cflags='-arch i386' --extra-ldflags='-arch i386'
5.输入make命令
6.将libavcodec.a，libavdevice.a，libavformat.a，libavutil.a，libswscale.a到对应的目录下拷贝出来。
7.在项目中就可以使用了。可以参考开源示例iFrameExtractor （git clone git://github.com/lajos/iFrameExtractor.git）需要将该项目的ffmpeg文件夹库替换为你编译的ffmpeg源码文件夹，在ffmpeg目录下新建lib目录，将刚刚拷贝出来的静态库拷贝进去。打开项目，添加libbz2.1.0.dylib系统库文件。点击编译运行就可以使用了。
8.注意如果使用的是ffmpeg0.8.5的库的话iFrameExtractor中的codec_type需要修改为AVMEDIA_TYPE_VIDEO。（下同）
编译arm7版本，网上搜到的版本，完全按照以下步骤做就行了。可以编译出arm7的库。
1. 下载:
git clone git://github.com/lajos/iFrameExtractor.git
2. 编辑:
build_armv6和build_armv7,修改./configure后面的参数,主要是SDK版本.我的是4.3,修改为:
./configure --disable-doc --disable-ffmpeg --disable-ffplay --disable-ffserver --enable-cross-compile --arch=arm --target-os=darwin --cc=/Developer/Platforms/iPhoneOS.platform/Developer/usr/bin/gcc --as='gas-preprocessor/gas-preprocessor.pl /Developer/Platforms/iPhoneOS.platform/Developer/usr/bin/gcc' --sysroot=/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS4.3.sdk --cpu=arm1176jzf-s --extra-cflags='-arch armv6' --extra-ldflags='-arch armv6'
3. 编译:
出错,提示:
/Developer/Platforms/iPhoneOS.platform/Developer/usr/bin/gcc is unable to create an executable file.
C compiler test failed.
查看config.err文件,最后提示:
ld: file not found: /usr/lib/system/libcache.dylib for architecture armv7
collect2: ld returned 1 exit status
4. 重新修改configure参数为:
./configure --disable-doc --disable-ffmpeg --disable-ffplay --disable-ffserver --enable-cross-compile --arch=arm --target-os=darwin --cc=/Developer/Platforms/iPhoneOS.platform/Developer/usr/bin/gcc --as='gas-preprocessor/gas-preprocessor.pl /Developer/Platforms/iPhoneOS.platform/Developer/usr/bin/gcc' --sysroot=/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS4.3.sdk --cpu=cortex-a8 --extra-cflags='-arch armv7' --extra-ldflags='-arch armv7 -isysroot /Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS4.3.sdk' --enable-pic
5. 编译:
build_armv7
最后生成静态库,在lib目录和armv7目录.
6.用xcode打开iFrameExtractor.xcodeproj,现在编译会出错,需要修改几个地方:
左边选中工程,中间选中target,右面选中Build settings,在Architectures选项卡里面选择Architetures为Optimized(armv7),Base SDK为Latest iOS(iOS 4.3) Valid Architectures填写armv7.
编译目标选择iOS Device,当然,如果有连接电脑的设备,可以选择设备.
编译,提示:
Undefined symbols for architecture armv7:
"_BZ2_bzDecompressInit", referenced from:
_matroska_decode_buffer in libavformat.a(matroskadec.o)
"_BZ2_bzDecompressEnd", referenced from:
_matroska_decode_buffer in libavformat.a(matroskadec.o)
"_BZ2_bzDecompress", referenced from:
_matroska_decode_buffer in libavformat.a(matroskadec.o)
添加库libbz2.1.0.dylib,再次编译,OK通过
