Message-ID: <43604483.7070109@xmission.com>
From: Brad Midgley <bmidgley@xmission.com>
MIME-Version: 1.0
To: bluez-devel@lists.sourceforge.net
Subject: Re: [Bluez-devel] fixed-point sbc decoder
References: <C70061B183DE09419568AB2060C52A950104B2D3@arion.intra.local>
In-Reply-To: <C70061B183DE09419568AB2060C52A950104B2D3@arion.intra.local>
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Date: Wed, 26 Oct 2005 21:07:47 -0600

Victor,

> I'll take a look in coming days.

thanks... for now I'm running floating and fixed point side-by-side and
watching for sign errors to find overflow. I was putting too many
precision bits in the fixed point synmatrix and it was overflowing and
coming out with the wrong sign in the product...

hey I noticed something that doesn't look right:

#define SP8(val) (val >> SCALE_PROTO8_TBL)

this is used in the tables for the 32-bit encoder. but this is not right
for negative values. Their sign will flip because it's a logical (not
arithmetic) shift. it's safer to do something like:

#define SP8(val) (val/(1<<SCALE_PROTO8_TBL))

don't you think? the divide will be done at compile time and it will
preserve the sign bit.

Brad


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