First,download gas-preprocessor.pl

URL: https://github.com/yuvi/gas-preprocessor
copy 'gas-preprocessor.pl' to ./usr/local/bin/gas-preprocessor.pl

Then,
1.Get Source :
- svn co svn://svn.ffmpeg.org/ffmpeg/trunk .

2.Configure :
You need to chanege your sdk index :  iPhoneOS4.3.sdk
- ./configure --cc=/Developer/Platforms/iPhoneOS.platform/Developer/usr/bin/gcc --as='gas-preprocessor.pl /Developer/Platforms/iPhoneOS.platform/Developer/usr/bin/gcc' --sysroot=/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS4.3.sdk --extra-ldflags=-L/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS4.3.sdk/usr/lib/system --target-os=darwin --arch=arm --extra-cflags='-arch armv7' --extra-ldflags='-arch armv7' --prefix=compiled/armv7 --enable-pic --enable-cross-compile

3.Make :
- make

4. find . -name *.a
./libavcodec/libavcodec.a
./libavcore/libavcore.a
./libavdevice/libavdevice.a
./libavfilter/libavfilter.a
./libavformat/libavformat.a
./libavutil/libavutil.a
./libswscale/libswscale.a










5. replace *.a to libs path