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

Michael Niedermayer michaelni
Tue Jun 22 01:22:58 CEST 2010

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
it to them? Then do not be too eager to deal out death in judgement. For
even the very wise cannot see all ends. -- Gandalf
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 189 bytes
Desc: Digital signature
URL: <http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/attachments/20100622/7b0af05e/attachment.pgp>

More information about the ffmpeg-devel mailing list