[CELT-dev] improve CELT

nidaa muhsin nidaa_muhsin at yahoo.com
Sat Sep 25 09:10:06 PDT 2010

Thanks for the clarification


--- On Sat, 9/25/10, Timothy B. Terriberry <tterribe at xiph.org> wrote:

> From: Timothy B. Terriberry <tterribe at xiph.org>
> Subject: Re: [CELT-dev] improve CELT
> To: 
> Cc: celt-dev at xiph.org
> Date: Saturday, September 25, 2010, 11:20 AM
> > There are still several ways to
> improve CELT, such as by incorporating better
>  > psychoacoustic masking in the dynamic bit allocation.
> This is a difficult
>  > problem both because there are few bits available for
> coding the 
> allocation
>  > and because the analysis window is short.
> >
> > it is possible to implement that and what are the
> correct approaches to do that.
> Several people have tried, including Garf and Jean-Marc. No
> one has been 
> able to demonstrate an improvement, even when you don't
> count the 
> overhead required to signal the allocation, i.e., even when
> you flat-out 
> cheat. This does not mean it can't be done, but it does
> mean we don't 
> know how to do it.
> We have considered adding a method of coding a boost to one
> or two bands 
> (e.g., reusing the PVQ code), which is signaled with low
> probability. 
> That would have little impact on the normal case where it
> is not used, 
> but the lower the probability, the bigger the gain you'd
> have to get 
> from your psychoacoustics before it would be useful. The
> other drawback 
> is that if the feature is not used in practice, it will not
> be 
> well-tested, and thus unlikely to work if you ever do
> figure out how to 
> use it.
> If anyone _can_ identify a method of doing dynamic
> allocation that makes 
> a consistent improvement, that would be very useful. We are
> hoping to 
> finalize the bitstream in the near future, though, so there
> isn't a lot 
> of time left to try.
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