Re: Re: H.264 codec and optimization issues

The first thig I saw in the mentioned document is that the Interpolation filters consume alot
of CPU. There's a nice MMX implementation suggested
in the jvt ftp pattaya JVT-G025.pdf that's worth examination.

The second "disease" of this codec is the huge amount of function calls, alot of cpu 
time is wasted on them (especially when you get alot of 4x4 subblocks), so smart data structure
and codec design is crucial.


<[email protected]>
Re: [Hdot264-devel] H.264 codec and optimization issues

    I believe that the lesson that should be learned from this paper it's that the way
to optimization comes first from doing detailed profiling to see where the performance
penalties come from.  Real life experience is full of cases of huge blind optimization
efforts that at the end result in to significant speed-ups because the bottleneck was
not there.

    Another lesson is that in H.264 ( and in all codecs in general), the performance
hot-spots are located in a few "kernels" ( like transform, SAD, VLC...).  In this
aspect, the eventual performance penalties deriving from a "clean" implementation
will not impact performance in any significant way, since the bottlenecks will lie
into those kernels.

----- Original Message ----- 
From: Indrajit Chakrabarty 
To: [email protected] 
Sent: Monday, March 31, 2003 10:54 AM
Subject: [Hdot264-devel] H.264 codec and optimization issues


Dear All
Please have a look at the following paper "Implementation of H.264 decoder on general-purpose processors with media instructions" which is available at
http://www.ee.princeton.edu/~ykchen/publications/H264.html
This paper talks about several modules in the JVT codec and there is an interesting discussion about the implementation and optimization of the inverse transform using shifts and adds only. In the end, for an SSE/SSE2 or even MMX implementation, using shifts and adds may not be very optimal!

Cheers,
Indrajit





Do you Yahoo!?
Yahoo! Platinum - Watch CBS' NCAA March Madness, live on your desktop!

-----------------------------------------------------------------------
Walla! Mail, Get Your Private, Free E-mail from Walla! at:
http://mail.walla.co.il