[FFmpeg-devel] [Fwd: Summer of code small task patch]

[Michael Niedermayer]

On Mon, Mar 30, 2009 at 10:52:32PM +0200, Dylan Yudaken wrote:
> Michael Niedermayer wrote:
>>
>>> Also - in the earlier versions of my code the IDCT was wrong. I have 
>>> fixed it now but it doesnt get the exact values of the previous versions. 
>>> My version has a lower error^2 but a higher systematic error. I dont have 
>>> much experience to tell if this trade off is acceptable.
>>>     
>>
>> it would be nice if your code would produce the same values as the current
>> ref in svn
>>
>>   
> does so now. it meant I had to take out that whole optimizing thing. most 
> of the other comments were related to this so they are fixed.

[...]

> --- a/libavcodec/Makefile
> +++ b/libavcodec/Makefile
> @@ -541,4 +541,4 @@ DIRS = alpha arm bfin mlib ppc ps2 sh4 sparc x86
>  
>  include $(SUBDIR)../subdir.mak
>  
> -$(SUBDIR)dct-test$(EXESUF): $(SUBDIR)fdctref.o $(SUBDIR)aandcttab.o
> +$(SUBDIR)dct-test$(EXESUF): $(SUBDIR)dctref.o $(SUBDIR)aandcttab.o

functional change


> diff --git a/libavcodec/dct-test.c b/libavcodec/dct-test.c
> index 0e27e1c..82e4137 100644
> --- a/libavcodec/dct-test.c
> +++ b/libavcodec/dct-test.c
> @@ -46,9 +46,9 @@
>  void *fast_memcpy(void *a, const void *b, size_t c){return memcpy(a,b,c);};
>  
>  /* reference fdct/idct */
> -void fdct(DCTELEM *block);
> -void idct(DCTELEM *block);
> -void init_fdct(void);
> +void ff_ref_fdct(DCTELEM *block);
> +void ff_ref_idct(DCTELEM *block);
> +void ff_ref_dct_init(void);

cosmetic change

please split these in 2 patches

[...]
> +    /* out = coefficients*block */
> +    for (i = 0; i < 64; i+=8) {
> +        for (j = 0; j < 8; ++j) {
> +            double tmp = 0;
> +            for (k = 0; k < 8; ++k) {
> +                /* cast the block - dont want overruns */
> +                tmp += coefficients[i + k] * ((int)block[k * 8 + j] * 8);
> +            }
> +            out[i + j] = tmp;
> +        }
> +    }

the *8 can be factorized out


[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Observe your enemies, for they first find out your faults. -- Antisthenes
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