[FFmpeg-devel] [PATCH] h264 CAVLC coeff_token decoder based on CLZ

[Michael Niedermayer]

On Sat, Jan 23, 2010 at 04:15:28PM -0800, Jason Garrett-Glaser wrote:
> On Sat, Jan 23, 2010 at 11:03 AM, Pascal Massimino
> <pascal.massimino at gmail.com> wrote:
> > On Sat, Jan 23, 2010 at 10:18 AM, Michael Niedermayer <michaelni at gmx.at>wrote:
> >
> >> On Sat, Jan 23, 2010 at 03:28:53AM +0300, Anatoliy Nenashev wrote:
> >> > Hi all!
> >> > I have made some investigations in H264 CAVLC coeff_token decoder.
> >> > In attached patch you can see special implementation of VLC decoder for
> >> > coeff_token which is based on CLZ (count leading zeros).
> >> > This method reduce size of VLC decoding tables for coeff_token from
> >> > (520+332+280+256)*2 = 2776 byte to (2*4*16 + 64 + 67 + 63 + 63) = 385
> >> byte.
> >>
> >
> > FWIW: these table are not called that often,
> 
> ~8-24 times per MB isn't that often?

at least 12 times per MB isnt often because the loop filter SSE2 code is
writen in yasm and thus cant be inlined forcing us to do 12 calls per MB
;)
thats in addition to the 12 calls that we have to do because gcc cant
inline a bunch of trivial wraper functions without messing up. I would have
loved to try to inline the SSE2 code in these wraper functions ...

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

The educated differ from the uneducated as much as the living from the
dead. -- Aristotle 
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