Elektronika 2009-11.pdf - Instytut Systemów Elektronicznych

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The use of speech recognition and user verification
in closed-circuit television systems
(Zastosowanie rozpoznawania mowy i weryfikacji użytkownika
w systemach telewizji przemysłowej)
dr inż. MARIUSZ KUBANEK
Politechnika Częstochowska, Instytut Informatyki Teoretycznej i Stosowanej
Speech recognition systems, and the verification of persons
on the basis of independent speech are widely used. Speech
is the most natural way for humans to communicate with each
other. Over the past decade, much work has been done in
man-machine communications in order to incorporate speech
as a new modality in multimedia applications. The greatest interest
is in two areas which have received considerable interest:
speech recognition, in which the aim is for the machine to
extract and understand the linguistic message in the speech,
and speaker recognition, where the goal is to identify, recognize
or verify the speaker responsible for producing the
speech. Speech recognition systems are used in mobile
phones for dial voice, in operating systems to voice control of
different applications, in text editors to impose sentences, to
recognize voice commands in cars, etc. User identification and
verification based on speech are most often used in access
control systems. The variety of applications of automatic
speech recognition systems, for human computer interfaces,
telephony, or robotics has driven the research of a large scientific
community [1,3].
The most important problem in process of speech recognition
and speaker identification or verification is suitable coding
of signal audio [4]. In general, speech coding is a procedure to
represent a digitized speech signal using a few bits as possible,
maintaining at the same time a reasonable level of speech quality.
Speech coding has matured to the point where it now constitutes
an important application area of signal processing. Due
to the increasing demand for speech communication, speech
coding technology has received augmenting levels of interest
from the research, standardization, and business communities.
Advances in microelectronics and the vast availability of lowcost
programmable processors and dedicated chips have enabled
rapid technology transfer from research to product
development; this encourages the research community to investigate
alternative schemes for speech coding, with the objectives
of overcoming deficiencies and limitations. To
standardization community pursues the establishment of standard
speech coding methods for various applications that will
be widely accepted and implemented by the industry. The business
communities capitalize on the ever-increasing demand
and opportunities in the consumer, corporate and network environments
for speech processing products [1,4].
In this work, it was proposed use speech recognition
method to control the movement of the camera of closed-circuit
television system, and use user verification method to log
on to this system. To extraction of the audio features of person’s
speech, in this work it was applied modified mechanism
of cepstral speech analysis. For acoustic speech coding was
used twenty dimensional MFCC (Mel Frequency Cepstral Coefficients)
as the standard audio features. Speech recognition
is done using hidden Markov models.
Preliminary process of signal
Analysis of audio channel one should to begin from filtration
of signal, removing elements of signal being him disturbances.
In working system in conditions approximate to ideal it was
been possible to skip stage of preliminary filtration in aim of
acceleration of working. In real conditions of work, signal of
audio speech is often considerably disturbed, therefore in
work was applied preliminary filtration [2].
In system of recognizing of isolated word to control the
movement of the camera of closed-circuit television, during
recordings is necessary making a short-lived but clear pauses
in form of silence among individual words. In view of remember
kind of recognizing, after preliminary filtration of signal
next stage is emission clean, proper audio signal, across removal
of silence from before and behind signal [2]. In this
work, it was applied two joint methods of removing of redundancy
silence. First, from the base on calculation energy of
signal and rejection of all samples, no exceeding receive
threshold of energy. Entrance signal is divided onto frame
boxes of 256 samples. Size of frame boxes depends from frequency
of sampling. It was applied frequency of sampling
8000 Hz. Then for every frame box is counted her energy.
Choosing suitably threshold it was been possible to mark
frame box, including beginning of recorded word. Such frame
box crosses receive threshold of energy. Since in moment of
beginning of recording, first some frame boxes contain only
silence, it was been possible to mark threshold of energy on
basis of initial frame boxes. In work, it was accepted doubled
sum of energy of three first frame boxes as threshold. Second
from methods counts number of changes of value of samples
of signal from smaller on larger and onto retreat, in
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