<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"> <HTML> <HEAD> <META NAME="GENERATOR" CONTENT="SGML-Tools 1.0.9"> <TITLE>The CVoiceControl Handbook: Technical Issues </TITLE> <LINK HREF="index-5.html" REL=next> <LINK HREF="index-3.html" REL=previous> <LINK HREF="index.html#toc4" REL=contents> </HEAD> <BODY> <A HREF="index-5.html">Next</A> <A HREF="index-3.html">Previous</A> <A HREF="index.html#toc4">Contents</A> <HR> <H2><A NAME="s4">4. Technical Issues </A></H2> <P> <H2><A NAME="sound-recording"></A> <A NAME="ss4.1">4.1 Sound Recording</A> </H2> <P> <P>Sound is recorded at 16 kHz, 16 bit, mono. This should be supported by any state-of-the-art standard sound card ?! <P><B>Note:</B> <P>To be able to record sound data (on a Linux system) you need to introduce a user group that is allowed to access the sound device. In the following explanation I will assume that <CODE>/dev/dspW</CODE> is the sound device we want to use, <CODE>audio</CODE> is the name of the group that we want to grant access to the sound device and <CODE>bill</CODE> is the user id of the user who wants to use CVoiceControl. <P>To introduce the user group <CODE>audio</CODE> and to add the user <CODE>bill</CODE> to this group and to make sure that the new group may record from the sound device, open a console window and type (as <CODE>root</CODE>): <P> <BLOCKQUOTE><CODE> <PRE> adduser --group audio adduser bill audio chgrp audio /dev/dspW chmod g+r /dev/dspW </PRE> </CODE></BLOCKQUOTE> <P>Now "ls -l /dev/dspW" should output something like <P> <BLOCKQUOTE><CODE> <PRE> crw-rw--w- 1 root audio 14, 5 Jan 9 22:38 /dev/dspW </PRE> </CODE></BLOCKQUOTE> <P>Then you have to restart Windows to complete the installation ;-) <P>For answers to further questions concerning Linux and sound have a look at the Linux Sound-HOWTO which is available from ftp://metalab.unc.edu/pub/Linux/docs/HOWTO/Sound-HOWTO <P> <H2><A NAME="ss4.2">4.2 Recognizer Details</A> </H2> <P> <P> <UL> <LI>Isolated word recognition </LI> <LI>Template matching using non-linear time normalization (DTW) <UL> <LI>DTW, using symmetric Sahoe&Chiba warping function</LI> <LI>Starting corner sloppiness: 4</LI> <LI>Parallel warping planes and Branch&Bound recognition</LI> <LI>Nearest neighbour wins template matching (roughly)</LI> </UL> </LI> <LI>Preprocessing: <UL> <LI>Hamming window</LI> <LI>Fast Hartley Transform (FFT) to calculate power spectrum</LI> <LI>(log) melscale coefficients</LI> <LI>Channel mean substraction</LI> <LI>IMPORTANT: Amplitude normalization is not yet performed on the wave data so it is important to keep about the same distance between microphone and mouth and to speak at about a constant loudness level</LI> </UL> </LI> </UL> <P> <HR> <A HREF="index-5.html">Next</A> <A HREF="index-3.html">Previous</A> <A HREF="index.html#toc4">Contents</A> </BODY> </HTML>
