[FFmpeg-devel] [PATCH] mpeg2: fix block_last_index when mismatch control modifies last coeff

[Michael Niedermayer]

On Mon, Jun 21, 2010 at 11:42:01PM +0100, M?ns Rullg?rd wrote:
> Jason Garrett-Glaser <darkshikari at gmail.com> writes:
> 
> > On Mon, Jun 21, 2010 at 3:23 PM, Michael Niedermayer <michaelni at gmx.at> wrote:
> >> I dont understand your problem, nor can i relate your rant to the
> >> existing code The code as is, is fast, simple and there are no
> >> special cases in any idct currently You seem to start your
> >> argumentation on the need of a change.
> >
> > We are trying to make things a lot faster.  You are stopping us
> > because we may need to make something very marginally slower in order
> > to get the large speed boost.  You're stopping us from adding a larger
> > engine to a racecar because the bigger exhaust pipe would slightly
> > increase drag.
> >
> > I'm trying to merge parts of a local changeset I have that makes the
> > FLV decoder 30-40% faster overall (many parts may apply to mpegvideo
> > overall).  Some of these parts are unmergable, but others are quite
> > mergable.  And you're stopping us from merging them because we might
> > strip 2 clocks off one function to improve another by 150.
> 
> The corrected block_last_index for mpeg2 will have _no effect at all_
> immediately.  When the idct is optimised, it will be faster when a
> shortcut is possible, unchanged otherwise.  It is true that without
> lots of extra work, mpeg2 will not get the full benefit of such
> optimisations.  However, without the fix, mpeg2 decoding will break
> with the optimised idct.  

why would it break?
I would have expected that we would have a function pointer to a dc idct
that could just be made to point to the normal idct for mpeg2
(and keep in mind we talk about changes that ive never seen)


> Fixing it will allow the idct optimisation
> to be done without complications. 

> If someone wants to squeeze more
> speed out of mpeg2, that can be done later.

of course

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

Many that live deserve death. And some that die deserve life. Can you give
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even the very wise cannot see all ends. -- Gandalf
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