[FFmpeg-devel] [PATCH] modification of the MMX H264 MC chroma functions to support RV40

[Mathieu Velten]

2008/12/23 Michael Niedermayer <michaelni at gmx.at>:
> On Tue, Dec 23, 2008 at 02:19:56AM +0100, Mathieu Velten wrote:
>> 2008/12/23 Michael Niedermayer <michaelni at gmx.at>:
>> > you are not doing ff_pw_tab[bias>>3], you are doing
>> > "*ff_pw_tab[bias] >>3"
>> >
>> in this case it is the same.
>
> yes both can be done by changing the table
>
> hint:
> %2 and 8+%2 can be then used to address both the original and
> the >>3 variant

Sorry I don't understand what you mean. Should I use an other table
(rv40_bias_div_8 for example) and pass the bias for the 1-dimensional
case in the function call too ?
or use a bigger rv40_bias table and use a shift to find the >>3
variant in the table ?

>>  {
>> -    const uint64_t *rnd_reg;
>>      DECLARE_ALIGNED_8(uint64_t, AA);
>>      DECLARE_ALIGNED_8(uint64_t, DD);
>>      int i;
>> @@ -45,17 +44,16 @@
>>          /* 1 dimensional filter only */
>>          const int dxy = x ? 1 : stride;
>>
>> -        rnd_reg = rnd ? &ff_pw_4 : &ff_pw_3;
>> -
>>          __asm__ volatile(
>>              "movd %0, %%mm5\n\t"
>>              "movq %1, %%mm4\n\t"
>> -            "movq %2, %%mm6\n\t"         /* mm6 = rnd */
>> +            "movq %2, %%mm6\n\t"
>> +            "psrlw $3, %%mm6\n\t"        /* mm6 = bias >> 3 */
>>              "punpcklwd %%mm5, %%mm5\n\t"
>>              "punpckldq %%mm5, %%mm5\n\t" /* mm5 = B = x */
>>              "pxor %%mm7, %%mm7\n\t"
>>              "psubw %%mm5, %%mm4\n\t"     /* mm4 = A = 8-x */
>
>> -            :: "rm"(x+y), "m"(ff_pw_8), "m"(*rnd_reg));
>> +            :: "rm"(x+y), "m"(ff_pw_8), "m"(*bias_reg));
>>
>>          for(i=0; i<h; i++) {
>>              __asm__ volatile(
>
> this renaming is purely cosmetic -> does not belong in this patch,
> besides i dont see the sense in it.

before the patch rnd was a "boolean" and it decided bias value
according to the boolean.
now the bias is directly passed to the function.

Mathieu Velten