GSoC Project status update 2: Speech Recognition in Open Moko

saurabh gupta saurabhgupta1403 at
Tue Jun 17 00:21:36 CEST 2008

hi Erland,

On Tue, Jun 17, 2008 at 2:04 AM, Erland Lewin <erland at> wrote:

> Hello Saurabh,
> 2008/6/16 saurabh gupta <saurabhgupta1403 at>:
>> So, I have written fixed point codes in which all calculations are handled
>> through fixed point. I have used the 16:16 notation for fixed point and used
>> 32 bit integer to represent a fixed point.
> FWIW, when I wrote an embedded speech recognition engine, I used 16 bits
> for most of the data in the models etc. If you could manage to store values
> in 16 bits rather than 32, then I your memory requirements could be halved,
> and probably performance increase significantly, since the cpu to memory
> bandwidth would be lower, and I think that might be a performance
> bottleneck. However, it required careful tracking of what range of values
> were actually required in various stages of the algorithm.

This was the point where I thought this way. Please correct me if I am
wrong. Since the word length of ARM processor of FR is 32bit, I chose 32 bit
size for the fixed point notation. In using 32 bit fixed point notation, my
range of both integer and fraction part also increases.

> Multiplication and division procedures for fixed point are implemented
>> through macros. As the project progresses, the stress will be given to
>> optimize the codes
>> more.
> I hope you won't have to do much if any division because division is quite
> slow. If there are variables you need to divide by, try storing 1/x instead
> of x, and then doing multiplication instead of division if you can manage
> that.

I did do that whenever I had to divide by the constant numbers. But at some
points, the situation happens to perform the division by run time variables
and so, I had to implement the fixed point division too.

> Good luck,
> Erland
> _______________________________________________
> Openmoko community mailing list
> community at

Saurabh Gupta
Electronics and Communication Engg.
NSIT,New Delhi
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