[FFmpeg-devel] [HOWTO] Building FFmpeg for iPhone

[David Conrad]

On Oct 2, 2009, at 6:47 PM, M?ns Rullg?rd wrote:

> David Conrad <lessen42 at gmail.com> writes:
>
>> On Oct 2, 2009, at 6:19 PM, M?ns Rullg?rd wrote:
>>
>>> David Conrad <lessen42 at gmail.com> writes:
>>>
>>>> On Oct 2, 2009, at 4:58 PM, M?ns Rullg?rd wrote:
>>>>
>>>>> 4a. For iPhone 3GS or iPod Touch 3G 32GB/64GB, use this command:
>>>>>  ./configure
>>>>> --cc=/Developer/Platforms/iPhoneOS.platform/Developer/
>>>>> usr/bin/arm-apple-darwin9-gcc-4.2.1 --as='gas-preprocessor.pl /
>>>>> Developer/Platforms/iPhoneOS.platform/Developer/usr/bin/arm-apple-
>>>>> darwin9-gcc-4.2.1' --sysroot=/Developer/Platforms/ 
>>>>> iPhoneOS.platform/
>>>>> Developer/SDKs/iPhoneOS3.1.sdk --enable-cross-compile --target-
>>>>> os=darwin --arch=arm --cpu=cortex-a8 --enable-pic
>>>>> 4b. For other iPhone or iPod Touch models, use this command:
>>>>>  ./configure
>>>>> --cc=/Developer/Platforms/iPhoneOS.platform/Developer/
>>>>> usr/bin/arm-apple-darwin9-gcc-4.2.1 --as='gas-preprocessor.pl /
>>>>> Developer/Platforms/iPhoneOS.platform/Developer/usr/bin/arm-apple-
>>>>> darwin9-gcc-4.2.1' --sysroot=/Developer/Platforms/ 
>>>>> iPhoneOS.platform/
>>>>> Developer/SDKs/iPhoneOS3.1.sdk --enable-cross-compile --target-
>>>>> os=darwin --arch=arm --cpu=arm1176jzf-s
>>>>> 5.  Run make.
>>>>>
>>>>> It is important to specify a correct --cpu option, and not  
>>>>> merely an
>>>>> architecture version.  Failure to specify the exact CPU will  
>>>>> give a
>>>>> broken build.
>>>>
>>>> You should add -arch armv7 to cflags and ldflags for 4a and -arch
>>>> armv6 for 4b (the warning about -force_cpusubtype_ALL indicates  
>>>> that
>>>> this will be required in the future.) This sets a specific cpu
>>>> subtype
>>>> for the mach-o file, which allows you lipo together binaries.
>>>
>>> I tried that, and got this error:
>>>
>>> cc1: error: unrecognized command line option "-arch"
>>>
>>> The warning is harmless, and only shows that Apple's compiler team  
>>> are
>>> a bunch of idiots, but we knew that already.
>>
>> Oops, -arch is only recognized by "gcc" not "arm-apple-darwin9-
>> gcc-4.2.1". So you'd need --cc=/Developer/Platforms/ 
>> iPhoneOS.platform/
>> Developer/usr/bin/gcc
>
> Oh, is that how it works.  Is this documented somewhere, or are you
> supposed to run "strings" on the binaries and guess?

It probably isn't documented for arm, but it comes from the method of  
making universal binaries where you call "gcc" with the matching -arch  
rather than calling <arch>-apple-darwin-gcc-4.2.1.