[Tremor] Re: [Vorbis-dev] Fixed point encoder for vorbis

[Hans Petter Selasky]

On Tuesday 20 December 2005 16:55, Robin Getz wrote:
> Hi.
>
> I was wondering if there is any work on a fixed point encoder for vorbis?
> If not, does anyone want to help with something?
>
> The purpose would be to make an icecast server on a low cost Linux
> platform, like Blackfin/uClinux, which doesn't have a floating point unit,
> but does have plenty of fixed point mips.
>

Hi,

I am planning a master project for next year, at my school, where I will look 
at making Ogg Vorbis use integer arithmetics, among other things. One of the 
ideas I have is to use multiplicative division instead of regular division to 
reduce rounding errors and consequently noise. One challenge is to convert a 
multiplicative fraction back into its numerator and denumerator, but it is 
not impossible. Maybe one has to use tables.

Currently I have created a small floating point library that uses 
multiplicative fractions. I have created routines for square root, 
logarithmics and the exponential function. Here are some extracts:

http://home.c2i.net/hselasky/math/fp_num.c


Does anyone have any comments on this? 


Have anyone tried anything similar before?


--HPS