[FFmpeg-devel] [PATCH] HE-AAC v1 decoder try 4

Michael Niedermayer michaelni
Thu Feb 25 03:20:38 CET 2010

On Wed, Feb 24, 2010 at 07:36:53PM -0500, Alex Converse wrote:
> On Tue, Feb 16, 2010 at 6:19 PM, Alex Converse <alex.converse at gmail.com> wrote:
> > On Tue, Feb 16, 2010 at 6:01 PM, Alex Converse <alex.converse at gmail.com>
> > wrote:
> >>
> >> Notes:
> >> *All the computation time is spent in ff_sbr_apply() and it's
> >> children. If it isn't called from ff_sbr_apply() making it 100% faster
> >> isn't going to buy us anything.
> >> *Right now the synthesis filterbank is written on top on an MDCT. With
> >> appropriate SIMD functions it may make sense to move it to an FFT.
> >> Right now the MDCT version is much faster.
> >> *SIMD placeholder patch not included
> >
> > Wrong patch.
> > try 4.1 :)
> Since the last patch I beat on the decoder with the zzuf hammer and
> fixed a few minor things as well as addressing the feeback I've seen
> in this thread.
> So I'm trying to figure out where we stand on this:
> *Does the ffplay issue block this?

what ffplay issue?

> *Is the filterbank blocking this?

Someone should review the filterbank and surrounding code.
either the code as is is the simplest (i doubt it) or it can be
simplified, such review would probably more concretely point at where it
can be improved
in that sense the rest of the code likely also should be properly reviewed
and with review here i mean by someone who understands the algorithms

also as a rule of thumb, if one transform uses a imdct the other likely
can be done based on a mdct

btw, theres quite a bit of copying and shuffling of data in this and i
doubt is unavoidable ...

> *Is anybody interested in playing with the filterbank. If so I can
> give you pages. It's very self contained.

iam interrested but i dont have the time.
also a small selfconstained test application that can test random pieces of
code against the correct code would be usefull


Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Incandescent light bulbs waste a lot of energy as heat so the EU forbids them.
Their replacement, compact fluorescent lamps, much more expensive, dont fit in
many old lamps, flicker, contain toxic mercury, produce a fraction of the light
that is claimed and in a unnatural spectrum rendering colors different than
in natural light. Ah and we now need to turn the heaters up more in winter to
compensate the lower wasted heat. Who wins? Not the environment, thats for sure
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