Message-ID: <42C8B510.7080206@xmission.com>
From: Brad Midgley <bmidgley@xmission.com>
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To: BlueZ Mailing List <bluez-devel@lists.sourceforge.net>
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Subject: [Bluez-devel] sbc and fixed-point progress
Sender: bluez-devel-admin@lists.sourceforge.net
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Date: Sun, 03 Jul 2005 22:03:28 -0600

Guys,

just FYI...

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.

Brad


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