[FFmpeg-devel] [PATCH] Optimization of original IFF codec

[Michael Niedermayer]

On Mon, Apr 26, 2010 at 12:19:28AM +0200, Sebastian Vater wrote:
> Hi Michael!
> 
> Michael Niedermayer a ?crit :
> > On Sun, Apr 25, 2010 at 01:49:54PM +0200, Sebastian Vater wrote:
> >   
> >>> that loop then can be unrolled by a factor of 4 and its inside for the
> >>> uint8_t type case be implemented like:
> >>>     v= lut[get_bits(&gb, 4)];
> >>>     AV_WN32A(dst+b, AV_RN32A(dst+b) | v);
> >>>   
> >>>       
> >> The thing is that type can be both uint8_t and uint32_t. It's a #define
> >> macro which gets the type (uint8_t or uint32_t) passed by.
> >>
> >> So not fixed yet because I'm unsure here, if those two lines can be done
> >> with dst being uint32_t also.
> >>     
> >
> > they can, and it will speed the uint8 case up significantly
> >   
> When I understand you right, I have to create a lookup table the
> following way:
> For each of the 4-pair read bits:
> {0000 = 0, 0001 = 1 << plane, 0010 = 0x100 << plane, 0011 = (1 << plane)
> | (0x100 << plane), 0100 = (0x10000 << plane), ...}
> 
> Is that correct?

yes, with endianness correct

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

Many that live deserve death. And some that die deserve life. Can you give
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