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

Jaska Uimonen
2008-11-28T13:35:37Z

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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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