[Mplayer-dev-eng] VP3 Codec

[Nick Kurshev]

Hello, Felix!
On Sat, 22 Sep 2001 16:08:24 +0200, you wrote:

> On Saturday, 22. September 2001 02:15, Arpi wrote:
> > Hi,
> >
> > > > > > 0x10004bd6:     mov    %cr0,%edx
> > > > >
> > > > > Oops.  So a Win32 DLL can mess with %cr0?  Amazing.
> > > >
> > > > yes. you know their slogen: win98 - everything possible
> > > >
> > > > btw that routine just checks some flags in cr0, and depending on their
> > > > value returns eax=0 or eax=1. i think thet can be replaced by a mov
> > > > eax,0/1 and many nops.
> > >
> > > the codec seems to use much asm code, maybe it's some sort of cpu feature
> > > detection.
> >
> > yes:
> >
> > ; check to see if OS supports SIMD instructions
> >     mov     edx,cr0
> >     bt      edx,2                           ; ensure no emulation
> >     jnae    NoXMMSupport
> >
> >     mov     edx,cr4
> >     bt      edx,9                           ; OS support SIMD
> >     jnc     NoXMMSupport
> >
> > ; we support XMM instructions
> >     mov     eax,1
> >     jmp     Exit
> >
> > NoXMMSupport:
> > ;    mov     eax,0                           ; OS does not support XMM
> > instructi
> >
> > so it uses cr0 to check OS support of SSE. this is why it works for
> > Gabucino (his k6 has no sse at all) and crashes for you.
> >
> I've now hacked the vp31vfw.dll removing this check and always assuming os 
> supports sse (so eax==1). I've uploaded the hacked dll to ftp://mphq/.../vp3/.
> I get green picture with YUY2 and black picture with bgr(16) :(
> 
> @ Nick: please fix biew search option for disassembler mode, it's very buggy 
> (doesn't find search results, or finds wrong stuff with one byte searches, ie 
> search for 73 find FF ans stuff like that, I'm using latest p7 version from 
> aug, 11th).
Yes - it's a bug. Thanks you very much!!!
Currently I suggest you to find following constructions:
jn?
with set flags:
- use wildcard (by F6)
- use plugin's output (by F7)
or simply:
jnc
if you want.
Using instruction's mnemonics within search dialog in disassembler mode makes
your search much easy and fanny.
> >
> > A'rpi / Astral & ESP-team
> 
> -- 
> Best Regards,
> 	Atmos
> 
> _____
> Ever tried? Ever failed? No Matter. Try again. Fail again. Fail Better.
> 	- Samuel Becket
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> 


Best regards! Nick