[XviD-devel] Porting Xvid ASM

Edouard Gomez ed.gomez at free.fr
Thu Sep 15 18:11:05 CEST 2005

Michael Weiss (mjw at pobox.com) wrote:

> Hi,
> I was wondering if any of you who knew the internals of the Xvid codec
> could  comment  on  what  it  would  be like  porting  it  to  another
> OS--VxWorks in this case, still Intel x86 architecture, though.  I was
> particularly wondering  about the parts  that are written  in assembly
> language.  Are these just optimized  versions of algorithms or do they
> make calls into the kernel, which would pose a big problem because I'd
> be switching kernels.  Sorry for all of the questions, but I am trying
> to establish ASAP whether what I am trying to do is actually feasible.
> Thanks,

To port to another OS you need:
 - See if there is compiler support for your OS in portab.h.
 - Make sure ./configure knows about your platform triple.

That's all, if any of these requirements aren't met, then specific
sections must be added to portab.h and configure.in to support vxworks
(i think mostly about the shared lib extension and little details that
vary among unixes)

The assembly code is just algorithms, absolutly no system code is used
inside of it. So just make sure the compiler C ABI follows the usual
IA32CABI which consists in pushing arguments to the stack upside down
the call stack. That's all.

Edouard Gomez

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