How to cross compile ffmpeg for iOS (iPhone and iPad)

출처 : http://blog.fh-kaernten.at/wehr/?p=1764

In one of my latest projects I needed some audio/video streaming capabilities for iOS driven devices.

The first App. which we implemented was a audio/HDVideo low latency conference streaming application for smart phones.

The second app was around  MPEG-TS to Elementary Stream demuxer for some dreambox streaming fun

The framework of choice is the swiss army knife for streaming stuff,.. ffmpeg. To be more precise, ffmpeg consists of serveral libraries and the command line programs ffmpeg, ffplay, ffprobe.

What do you need:

• Xcode4.3
• Apple’s command line tools (Xcode -> Preferences -> Components)
• pkg-config -> download
• gas-preprocessor -> download (extract under your ffmpeg root dir ./gas-preprocessor)
• build-essentials -> you can download an install script

• m4
• autoconf
• automake
• libtool

• last but not least ffmpeg -> download

I used the latest snapshot available at the the time of writing. Extract the snapshot .tar to a folder of our choice.

Thanks Michael, the lead developer of ffmpeg, the ffmpeg source comes with the convenient autotools facilities. So we only need to set the correct configure flags

1. Compiler flags:

As we need to do some cross-compiling we need to select the compiler/assembler which comes with our XCode

–cc=’/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/usr/bin/arm-apple-darwin10-llvm-gcc-4.2′.

–as=’./gas-preprocessor/gas-preprocessor.pl /applications/xcode.app/contents/Developer/Platforms/iPhoneOS.platform/Developer/usr/bin/arm-apple-darwin10-gcc-4.2′

–arch=arm

–target-os=darwin

–cpu=cortex-a8

–enable-pic

–disable-yasm

2. iOs SDK path:

–sysroot=’/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS5.1.sdk’

3. extra flags:

–extra-cflags=’-mfpu=neon -pipe -Os -gdwarf-2 -miphoneos-version-min=5.0′

–extra-ldflags=’-arch armv7 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS5.1.sdk -miphoneos-version-min=5.0′

4. configure ffmpeg library components:

for example:

 –disable-ffmpeg
–disable-ffplay
–disable-ffprobe
–disable-ffserver
–disable-avdevice
–disable-avfilter
–disable-everything

and then enable the components you need

–enable-decoder=xxx
–enable-parser=xxx
–enable-demuxer=xxx

after successful completion of ./configure run make… and voilà

If you get some errors complaining about  “error: invalid operand in inline asm: ” try to disable assembler directives with

–diasble-asm

have fun

Mario