GSoC Project status update 2: Speech Recognition in Open Moko

Erland Lewin erland at
Mon Jun 16 22:34:23 CEST 2008

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.

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

Good luck,

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