[XviD-devel] About xvid source assembly language optimize(why it does not work?)

Michael Militzer michael at xvid.org
Tue Nov 18 18:05:28 CET 2008


make sure you really compiled xvid with assembly optimizations enabled. You
need yasm or nasm present - or otherwise xvid will be compiled with c-code

Also note that the -m option will write out data to your disk. It might be
that more time is spent on I/O than on the actual decoding. In that case,
asm and noasm options could seem to perform similar.


Quoting ?? <bing.li at autosoft.com.cn>:

> Dear  Everybody:
>    I download the  xvid 1.1.3 source code , and i compiled the   
> source  under Fedora Core 8.
>   Then I compile xvid_decraw.c.
>   And I run with the command:
>   ./xvid_decraw   -i input.m4v   -m
>   then it work well, and output the bitmap file. but it is rather slow.
>   Then I use the command below:
>   ./xvid_decraw   -i input.m4v   -asm -m
>   Hence I think i used  -asm option ,  the decoding speed should be   
>  accelerated.
>   But .... I find that the result is unchanged with the  non-asm   
> execution result .
>   input.m4v is a raw 720x568 mpeg4 video sequence, .
>   I wonder whether the -asm  option worked!
>   So i test  the fdct and idct, they have been assigned to    
> fdct_mmx_skal and idct_mmx respectly.
>   But why it does not accelerate?
>   So i use a small script to test the  fdct_c and  fdct_mmx_skal.    
> To run 1000000 times ,
>   the fdct_c consume 2.7 seconds  and fdct_mmx_skal need 0.8 second   
> on my computer.
>   It seems that asm code should be much faster.  But why xvid   
> decoding can not be speeded up?
>   Thanks very much !
> 2008-11-18
> Ice Lee
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