Re: [Bluez-devel] sbc and fixed-point progress

[Marcel Holtmann <marcel@holtmann.org>]

Hi Brad,

> I found a decent fixed point multiply that preshifts the values before
> multiplying them. It keeps things in 32 bits. Most of the roundoff error
> is taken care of in two additional terms. I think the result is
> reasonable.
> (http://www.accu.org/acornsig/public/caugers/volume2/issue6/fixedpoint.html)
> 
> If you compile with fixed-point on, libsbc will run both the
> fixed and floating point calculations and flag errors when they differ
> too much. It seems to be working well and has helped me catch a couple
> of fixed-point calculation problems.
> 
> I have the decoder almost finished but I probably need to split some 
> terms into integer and fixed-point components. Loading up 
> frame->sb_sample for example can have a big integer part but we want to 
> use most of the 32 bit fixed-point type for the fractional part.

go ahead and keep on with the good work.

However someone might be looking at the SBC algorithm itself. I've been
told that there are a lot of optimizations possible.

Regards

Marcel




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