<HR>

<H2><A name=random>Random Number Generation</A></H2>
<UL>
  <LI>The routine <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/randvec.txt">randvec 
  </A>generates random vectors with a given mean and covariance. 
  <LI>The routine <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/usasi.txt">usasi 
  </A>generates noise with a USASI spectrum. 
  <LI>The routine <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/randfilt.txt">randfilt</A> 
  generates filtered gaussian noise without any startup transients. </LI></UL>
<HR>

<H2><A name=distance>Vector Distance</A></H2>
<UL>
  <LI>The routine <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/disteusq.txt">disteusq 
  </A>calculates the squared euclidean distance between all pairs of rows of two 
  matrices. 
  <LI>The routines <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/distitar.txt">distitar</A>, 
  <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/distisar.txt">distisar</A> 
  and <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/distchar.txt">distchar</A> 
  calculate the Itakura, Itakura-Saito and COSH spectral distances between sets 
  of AR coefficients. 
  <LI>The routines <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/distitpf.txt">distitpf</A>, 
  <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/distispf.txt">distispf</A> 
  and <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/distchpf.txt">distchpf</A> 
  calculate the Itakura, Itakura-Saito and COSH spectral distances between power 
  spectra. </LI></UL>
<HR>

<H2><A name=analysis>Speech Analysis</A></H2>
<UL>
  <LI>The routine <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/enframe.txt">enframe</A> 
  can be used to split a signal up into frames. It can optionally apply a window 
  to each frame. 
  <LI>The routine <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/ewgrpdel.txt">ewgrpdel</A> 
  calculates the energy-weighted group delay waveform. 
  <LI>The routine <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/activlev.txt">activlev 
  </A>calculates the active level of a speech segment according to ITU-T 
  recommendation P.56. 
  <LI>The routine <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/spgrambw.txt">spgrambw 
  </A>draws a monochrome spectrogram with a dB scale. 
  <LI>The routine <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/schmitt.txt">schmitt 
  </A>passes a signal through a schmitt trigger. 
  <LI>The routine <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/txalign.txt">txalign</A> 
  finds the best alignment (in a least squares sense) between two sets of time 
  markers (e.g. glottal closure instants). </LI></UL>
<HR>

<H2><A name=enhance>Speech Enhancement</A></H2>
<UL>
  <LI>The routine <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/specsubm.txt">specsubm</A> 
  implements spectral subtraction using an algorithm of Martin. </LI></UL>
<HR>

<H2><A name=lpc>LPC Analysis of Speech</A></H2>
<UL>
  <LI>The routines <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/lpcauto.txt">lpcauto</A> 
  and <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/lpccovar.txt">lpccovar</A> 
  perform linear predictive coding (LPC) analysis. The routines relating to LPC 
  are described in more detail on <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/lpc.html">another page</A>. 
  A large number of <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/lpc.html">conversion 
  routines</A> are included for changing the form of the LPC coefficients (e.g. 
  AR coefficients, reflection coefficients etc.): these are of the form lpcxx2yy 
  where xx and yy denote the coefficient sets. The routine <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/lpcrr2am.txt">lpcrr2am 
  </A>calculates LPC filters for all orders up to a given maximum. 
  <LI>The routine <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/lpcbwexp.txt">lpcbwexp 
  </A>performs bandwidth expansion on an LPC filter. 
  <LI>The routine <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/ccwarpf.txt">ccwarpf 
  </A>performs frequency warping in the complex cepstrum domain. 
  <LI>The routine <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/lpcifilt.txt">lpcifilt 
  </A>performs inverse filtering to estimate the glottal waveform from the 
  speech signal and the lpc coefficients. 
  <LI>The routine <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/lpcrand.txt">lpcrand</A> 
  can be used to generate random, stable filters for testing purposes. </LI></UL>
<HR>

<H2><A name=synthesis>Speech Synthesis</A></H2>
<UL>
  <LI>The routines <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/glotros.txt">glotros</A> 
  and <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/glotlf.txt">glotlf</A> 
  implement two common models for the waveform of airflow through the vocal 
  folds. </LI></UL>
<HR>

<H2><A name=coding>Speech Coding</A></H2>
<UL>
  <LI>The routines <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/lin2pcma.txt">lin2pcma</A>, 
  <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/lin2pcmu.txt">lin2pcmu</A>, 
  <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/pcma2lin.txt">pcma2lin</A>, 
  and <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/pcmu2lin.txt">pcmu2lin</A> 
  convert audio waveforms to and from the 8-bit A-law and Mu-law PCM formats 
  that are used in telecommunications: Mu-law is used in the USA and Japan while 
  A-law is used in the rest of the world. The two formats are very similar and, 
  for speech waveforms, give about the same perceived quality as 12-bit linear 
  encoding. Alternate bits in the A-law format are usually inverted before 
  transmission: the conversion routines can optionally include this. The 
  conversions are defined by ITU standard G.711. 
  <LI>The routines <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/kmeans.txt">kmeans 
  </A>and <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/kmeanlbg.txt">kmeanlbg 
  </A>perform vector quantisation using the kmeans algorithm. 
  <LI>The routine <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/potsband.txt">potsband 
  </A>calculates a bandpass filter corresponding to the standard telephone 
  passband. </LI></UL>
<HR>

<H2><A name=recog>Speech Recognition</A></H2>
<UL>
  <LI>The routine <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/melcepst.txt">melcepst 
  </A>implements a mel-cepstrum front end for a recogniser. The associated 
  bandpass filter matrix is generated by <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/melbankm.txt">melbankm 
  </A>. 
  <LI>The routines <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/cep2pow.txt">cep2pow 
  </A>and <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/pow2cep.txt">pow2cep 
  </A>convert state means and variances between the mel-cepstrum and power 
  domains. 
  <LI>The routine <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/gaussmix.txt">gaussmix</A> 
  fits a gaussian mixture distribution to a collection of observation vectors. 
  </LI></UL>
<HR>

<H2><A name=utility>Utility Functions</A></H2>
<UL>
  <LI><A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/voicebox.txt">voicebox</A> 
  contains a number of installation-dependent global parameters and may need 
  editing. 
  <LI>The routine <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/zerotrim.txt">zerotrim 
  </A>removes from a matrix any trailing rows and columns that are all zero. 
  <LI>The routine <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/logsum.txt">logsum</A> 
  calculates log(sum(exp(x))) without overflow problems. 
  <LI>The routine <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/dualdiag.txt">dualdiag</A> 
  simultaneously diagonalises two matrices: this is useful in computing LDA or 
  IMELDA transforms. 
  <LI>The routines <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/permutes.txt">permutes 
  </A>and <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/choosenk.txt">choosenk 
  </A>generate respectively all possible permutations of the numbers 1:n and all 
  possible ways of choosing k elements out of the numbers 1:n without 
  duplications. They are equivalent to the standard MATLAB routines PERMS and 
  NCHOOSEK but much faster. 
  <LI>The routine <A 
  href="http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/txt/zerotrim.txt">sprintsi 
  </A>prints a value with the correct standard SI multiplier (e.g. 2100 prints 
  as 2.1 k). </LI></UL></BODY></HTML>