[RFC/PATCH] sbc: new filtering function for 8 band fixed point encoding

[Jaska Uimonen <jaska.uimonen@nokia.com>]

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Hi All,

I did some testing on the current 8 band fixed point 
encoding and it seems to attenuate frequencies below 800Hz 
and above 18kHz. There might be some other stuff happening 
also, because at least to me the bass seemed to lack some 
"definition".

I didn't quite understand how the current tables are calculated
and how the filtering works so I wrote a new filtering function
and calculated new filter tables for it. It is written
using 16 bit fixed point without any platform specific optimizations.
I only unrolled some loops etc. I tried to follow the
flow chart in MPEG-1 annex c.

With this new filtering the low and high frequencies are there, but
I haven't done any more thorough testing. At least it sounds
a little bit better to my ears :)

br,
Jaska Uimonen

P.S. I could have done some discussion with the list members 
about the current implementation, but I kind of got carried away. 
Sorry about that.

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