[FFmpeg-devel] decoding MPEG4 ASP video on iPhone (armv6, armv7)

David Conrad lessen42
Wed Jan 13 22:46:19 CET 2010


On Jan 13, 2010, at 4:28 PM, Jason Garrett-Glaser wrote:

> On Wed, Jan 13, 2010 at 9:11 AM,  <michelle211 at comcast.net> wrote:
>> 
>> 
>> 
>> I have compiled ffmpeg/ffplay
>> 
>> 
>> 
>> When I play an avi or mpg with ffplay I get a green distorted video.
>> 
>> 
>> 
>> much like what is described here.
>> 
>> 
>> 
>> http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/2009-December/079791.html
>> 
>> 
>> 
>> The post mentions using -arch=c , does that help the issue.
>> 
>> 
>> 
>> Also I read somewhere on another post that the issue is related to sdl, is there a fix for that.
>> 
>> 
>> 
>> Has anyone gotten this to work correctly.
> 
> Just speculation, but this might be related to the fact that the
> iPhone/iPod compilers ignore the ARM ABI and don't maintain 8-byte
> stack alignment, which some functions might assume.

That should only affect Cortex-A8, and iirc Mans fixed the one place that assumed 8-byte alignment.

The specific function that causes issues is reportedly the armv6 idct (and armv5te), but even for users experiencing the issue it assembles correctly. And both work on an A8 iphone with the neon idct disabled.

I've jailbroken my 1g ipod touch and attempted to replicate the issue on the commandline, but everything worked perfectly for me.



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