GSoC Project Status Update 03: Speech Recognition Facility in Openmoko

saurabh gupta saurabhgupta1403 at
Sun Jun 22 19:44:11 CEST 2008

Hello everyone,

This is the status update of the GSoC project, Speech Recognition facility
in Openmoko. This week, much of the time was devoted in writing codes and
optimizing the existing one. I have written many subroutines like forward
backward procedure, LPC and cepstral analysis of speech signals in frames,
viterbi algorithm and training algorithm using K-means segmental method. All
the source codes have been successfully compiled using GNU C compiler.
     There are various optimizations done in the coding to make it suitable
for working on the ARM 16/32-bit processor running at 266 or 400 MHz
maximum. The whole code is written using fixed point arithmetic.  I used
some external libraries for some subroutines and converted them in fixed
point arithmetic. The other optimization was done by choosing K-means
segmental procedure for training the HMM models rather than Baum Welch
algorithm which requires more processing since it accounts for all the
possible hidden states for a given sequence. On the other hand K-means
segmental method uses viterbi algorithm to find the best state sequence and
then iterates for re-estimation and training the HMM model. K-means
segmental method has been proved to show good results and fast processing
than Baum-Welch. The other optimization is regarding the probability density
function. As this project aims for  a small vocabulary (around 5 or 10) for
recognition, vector quantization will be used instead of continuous
observation sequence. Vector quantization procedure is faster and yields
good result for applications in small embedded devices. The vector
quantization source code is about to finish. Soon after that, the actual
testing of speech recognition code will be done on the speech samples
           I have uploaded all Documents (Design Document version-0.2) and
source codes on the svn repository of Openmoko ( Any comments and
suggestions will be highly appreciated.

Saurabh Gupta
Electronics and Communication Engg.
NSIT,New Delhi
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