NetNews Usenet Archive 1992 #27/NN_1992_27.iso/spool/comp/speech/266

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From: [e-mail] (Andrew Hunt)
Subject: FAQ - First Draft
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                       comp.speech

                Frequently Asked Questions
                ==========================

(FAQ = "Frequently Asked Questions")

Compiled: 18-Nov-92

This document is an attempt to answer commonly asked questions and to
reduce the bandwidth taken up by these posts and their associated replies.
If you have a question, please check this file before you post.

The FAQ is not meant to discuss any topic exhaustively.  It will hopefully
provide readers with pointers on where to find useful information.  It also
tries to list as much of the useful information and material available
elsewhere on the Internet.

If you have not already read the Usenet introductory material posted to
"news.announce.newusers", please do.  For help with FTP (file transfer
protocol) look for a regular posting of "Anonymous FTP List - FAQ" in
comp.misc, comp.archives.admin and news.answers amongst others.


The document is an EARLY DRAFT.  There are many unanswered questions and
some answers are not comprehensive.  I hope that it will improve over the next
few months.  If you have any comments, suggestions for inclusions, or answers
then please post or email.

In particular, the sections listing software/hardware to perform both
synthesis, recognition and NLP have lots of gaps.


My appologies to those who have been awaiting the first posting.  I have
been on holidays for most of the last month.


Andrew Hunt
Speech Technology Research Group    email: [e-mail]
Department of Electrical Engineering    Ph:  61-2-692 4509
University of Sydney, Australia.    Fax: [phone]


========================== Acknowledgements ===========================

Thanks to the following for their comments and contributions.

Oliver Jakobs        <[e-mail]>
Tony Robinson        <[e-mail]>


============================ Contents =================================

PART 1 - General

Q1.1: What is comp.speech?
Q1.2: Where are the comp.speech archives?
Q1.3: Common abbreviations and jargon.
Q1.4: What are related newsgroups and mailing lists?
Q1.5: What are related journals and conferences?
Q1.6: What speech databases are available?
Q1.7: Speech File Formats, Conversion and Playing.

PART 2 - Signal Processing for Speech

Q2.1: What speech sampling and signal processing hardware can I use?
Q2.2: Signal processing techniques for speech technology.
Q2.3: How do I convert to/from mu-law format?

PART 3 - Speech Coding and Compression

Q3.1: Speech compression techniques.
Q3.2: What are some good references/books on coding/compression?
Q3.3: What software is available?

PART 4 - Speech Synthesis

Q4.1: What is speech synthesis?
Q4.2: How can speech synthesis be performed?
Q4.3: What are some good references/books on synthesis?
Q4.4: What software/hardware is available?

PART 5 - Speech Recognition

Q5.1: What is speech recognition?
Q5.2: How can I build a very simple speech recogniser?
Q5.2: What does speaker dependent/adaptive/independent mean?
Q5.3: What does small/medium/large/very-large vocabulary mean?
Q5.4: What does continuous speech or isolated-word mean?
Q5.5: How is speech recognition done?
Q5.6: What are some good references/books on recognition?
Q5.7: What packages are available?

PART 6 - Speaker Recognition/Verification

Q6.1: What is speaker recognition/verification?
Q6.2: Where is speaker recognition used?
Q6.3: What are techniques for speaker recognition?
Q6.4: How good is speaker recognition?
Q6.5: What are some good references/books on speaker recognition?
Q6.6: What packages are available?

PART 7 - Natural Language Processing

Q7.1: What is NLP?
Q7.2: What are some good references/books on NLP?
Q7.3: What software is available?

=======================================================================

PART 1 - General

Q1.1: What is comp.speech?

comp.speech is a newsgroup for discussion of speech technology and
speech science.  It covers a wide range of issues from application of
speech technology, to research, to products and lots more.

By nature speech technology is an inter-disciplinary field and the
newsgroup reflects this.  However, computer application should be the
basic theme of the group.

The following is a list of topics but does not cover all matters related
to the field - no order of importance is implied.

[1] Speech Recognition - discussion of methodologies, training, techniques,
results and applications.  This should cover the application of techniques
including HMMs, neural-nets and so on to the field.

[2] Speech Synthesis - discussion concerning theoretical and practical
issues associated with the design of speech synthesis systems.

[3] Speech Coding and Compression - both research and application matters.

[4] Phonetic/Linguistic Issues - coverage of linguistic and phonetic issues
which are relevant to speech technology applications.  Could cover parsing,
natural language processing, phonology and prosodic work.

[5] Speech System Design - issues relating to the application of speech
technology to real-world problems.  Includes the design of user interfaces,
the building of real-time systems and so on.

[6] Other matters - relevant conferences, books, public domain software,
hardware and related products.

------------------------------------------------------------------------

Q1.2: Where are the comp.speech archives?

comp.speech is being archived for anonymous ftp.

    ftp site:    svr-ftp.eng.cam.ac.uk (or 129.169.24.20).
    directory:    comp.speech/archive

comp.speech/archive contains the articles as they arrive.  Batches of 100
articles are grouped into a shar file, along with an associated file of
Subject lines.

Other useful information is also available in comp.speech/info.

------------------------------------------------------------------------

Q1.3: Common abbreviations and jargon.

ANN  - Artificial Neural Network.
ASR  - Automatic Speech Recognition.
CELP - Code excited linear prediction.
DTW  - Dynamic time warping.
FAQ  - Frequently asked questions.
HMM  - Hidden markov model.
LPC  - Linear predictive coding.
LVQ  - Linear vector quantisation.
NLP  - Natural Language Processing.
NN   - Neural Network.
TTS  - Text-To-Speech (i.e. synthesis).

------------------------------------------------------------------------

Q1.4: What are related newsgroups and mailing lists?


NEWGROUPS

comp.ai - Artificial Intelligence newsgroup.
     Postings on general AI issues, language processing and AI techniques.
     Has a good FAQ including NLP, NN and other AI information.

comp.ai.nlang-know-rep - Natural Language Knowledge Representation
     Moderated group covering Natural Language.

comp.ai.neural-nets - discussion of Neural Networks and related issues.
     There are often posting on speech related matters - phonetic recognition,
     connectionist grammars and so on.

comp.compression - occasional articles on compression of speech.
     FAQ for comp.compression has some info on audio compression standards.

comp.dcom.telecom - Telecommunications newsgroup.
     Has occasional articles on voice products.

comp.dsp - discussion of signal processing - hardware and algorithms and more.
     Has a good FAQ posting.
     Has a regular posting of a comprehensive list of Audio File Formats.

comp.multimedia - Multi-Media discussion group.
     Has occasional articles on voice I/O.

sci.lang - Language.
     Discussion about phonetics, phonology, grammar, etymology and lots more.


MAILING LISTS

ECTL - Electronic Communal Temporal Lobe
     Founder & Moderator: David Leip
     Moderated mailing list for researchers with interests in computer speech
     interfaces. This list serves a broad community including persons from
     signal processing, AI, linguistics and human factors.

     To subscribe, send the following information to:
        [e-mail]
        name, institute, department, daytime phone & e-mail address

     To access the archive, ftp snowhite.cis.uoguelph.ca, login as anonymous,
     and supply your local userid as a password.  All the ECTL things can be
     found in pub/ectl.

Prosody Mailing List
    Unmoderated mailing list for discussion of prosody.  The aim is
    to facilitate the spread of information relating to the research
    of prosody by creating a network of researchers in the field.
    If you want to participate, send the following one-line
    message to "[e-mail]" :-

        subscribe prosody Your Name

Digital Mobile Radio
     Covers lots of areas include some speech topics including speech
     coding and speech compression.
     Mail Peter Decker ([e-mail]) to subscribe.

------------------------------------------------------------------------

Q1.5: What are related journals and conferences?

Try the following commercially oriented magazines...

    Speech Technology

Try the following technical journals...

    Computational Linguistics
    Computer Speech and Language
    Journal of the Acoustical Society of America
    Transactions of IEEE ASSP

Try the following conferences...

    IEEE Intl. Conf. Acoustics, Speech and Signal Processing
    Intl Conf on Spoken Language Processing

------------------------------------------------------------------------

Q1.6: What speech databases are available?

A wide range of speech databases have been collected.  These databases
are primarily for the development of speech synthesis/recognition and for
linguistic research.  Unfortunately, almost all the information listed
here refers to the English language.

Some databases are free but most appear to be available for a small cost.
The databases normally require lots of storage space - do not expect to be
able to ftp all the data you want.

[There are too many to list here in detail - perhaps someone would like to
 set up a special posting on speech databases?]


LINGUISTIC DATA CONSORTIUM (LDC)

Information about the Linguistic Data Consortium is available via
anonymous ftp from:    ftp.cis.upenn.edu    (130.91.6.8)
in the directory:    /pub/ldc

Here are some excerpts from the files in that directory:

Briefly stated, the LDC has been established to broaden the collection
and distribution of speech and natural language data bases for the
purposes of research and technology development in automatic speech
recognition, natural language processing and other areas where large
amounts of linguistic data are needed.

Here is the brief list of corpora:

   * The TIMIT and NTIMIT speech corpora
   * The Resource Management speech corpus (RM1, RM2)
   * The Air Travel Information System (ATIS0) speech corpus
   * The Association for Computational Linguistics - Data Collection
     Initiative text corpus (ACL-DCI)
   * The TI Connected Digits speech corpus (TIDIGITS)
   * The TI 46-word Isolated Word speech corpus (TI-46)
   * The Road Rally conversational speech corpora (including "Stonehenge"
     and "Waterloo" corpora)
   * The Tipster Information Retrieval Test Collection
   * The Switchboard speech corpus ("Credit Card" excerpts and portions
     of the complete Switchboard collection)

Further resources to be made available within the first year (or two):

   * The Machine-Readable Spoken English speech corpus (MARSEC)
   * The Edinburgh Map Task speech corpus
   * The Message Understanding Conference (MUC) text corpus of FBI
     terrorist reports
   * The Continuous Speech Recognition - Wall Street Journal speech
     corpus (WSJ-CSR)
   * The Penn Treebank parsed/tagged text corpus
   * The Multi-site ATIS speech corpus (ATIS2)
   * The Air Traffic Control (ATC) speech corpus
   * The Hansard English/French parallel text corpus
   * The European Corpus Initiative multi-language text corpus (ECI)
   * The Int'l Labor Organization/Int'l Trade Union multi-language
     text corpus (ILO/ITU)
   * Machine-readable dictionaries/lexical data bases (COMLEX, CELEX)

The files in the directory include more detailed information on the
individual databases.  For further information contact

    Elizabeth Hodas
    441 Williams Hall
    University of Pennsylvania
    Philadelphia, PA 19104-6305
    Phone:   [phone]
    Fax:     [phone]
    e-mail:  [e-mail]


Center for Spoken Language Understanding (CSLU)

1. The ISOLET speech database of spoken letters of the English alphabet.
The speech is high quality (16 kHz with a noise cancelling microphone).
150 speakers x 26 letters of the English alphabet twice in random order.
The "ISOLET" data base can be purchased for $100 by sending an email request
to [e-mail].  (This covers handling, shipping and medium costs).
The data base comes with a technical report describing the data.

2. CSLU has a telephone speech corpus of 1000 English alphabets.  Callers
recite the alphabet with brief pauses between letters.  This database is
available to not-for-profit institutions for $100. The data base is described
in the proceedings of the International Conference on Spoken Language
Processing.  Contact [e-mail] if interested.

------------------------------------------------------------------------

Q1.7: Speech File Formats, Conversion and Playing.

Section 2 of this FAQ has information on mu-law coding.

A very good and very comprehensive list of audio file formats is prepared
by Guido van Rossum.  The list is posted regularly to comp.dsp and
alt.binaries.sounds.misc, amongst others.  It includes information on
sampling rates, hardware, compression techniques, file format definitions,
format conversion, standards, programming hints and lots more.

It is also available by ftp
    from:         ftp.cwi.nl
    directory:    /pub
    file:         AudioFormats<version>



=======================================================================

PART 2 - Signal Processing for Speech

Q2.1: What speech sampling and signal processing hardware can I use?

In addition to the following information, have a look at the Audio File
format document prepared by Guido van Rossum (referred to above).


Product: Sun standard audio port (SPARC 1 & 2)
Input:  1 channel, 8 bit mu-law encoded (telephone quality)
Output: 1 channel, 8 bit mu-law encoded (telephone quality)

Product:  Ariel
Platform: Sun + others?
Input:  2 channels, 16bit linear, sample rate 8-96kHz (inc 32, 44.1, 48kHz).
Output: 2 channels, 16bit linear, sample rate 8-50kHz (inc 32, 44.1, 48kHz).
Contact:

Can anyone provide information on Soundblaster, Mac, NeXT and other hardware?

[Help is needed to source more info.  How about the following format?]

Product:  xxx
Platform: PC, Mac, Sun, ...
Rough Cost (pref $US):
Input: e.g. 16bit linear, 8,10,16,32kHz.
Output: e.g. 16bit linear, 8,10,16,32kHz.
DSP: signal processing support
Other:
Contact:

------------------------------------------------------------------------

Q2.2: Signal processing techniques for speech technology.

Would anyone like to write a short intro, list some useful refs, and list
public domain signal processing software?

------------------------------------------------------------------------

Q2.3: How do I convert to/from mu-law format?

Mu-law coding is a form of compression for audio signals including speech.
It is widely used in the telecommunications field because it improves the
signal-to-noise ratio without increasing the amount of data.  Typically,
mu-law compressed speech is carried in 8-bit samples.  It is a companding
technqiue.  That means that carries more information about the smaller signals
than about larger signals.  Mu-law coding is provided as standard for the
audio input and output of the SUN Sparc stations 1&2 (Sparc 10's are linear).

Here is some sample conversion code in C.

# include <stdio.h>

unsigned char linear2ulaw(/* int */);
int ulaw2linear(/* unsigned char */);

/*
** This routine converts from linear to ulaw.
**
** Craig Reese: IDA/Supercomputing Research Center
** Joe Campbell: Department of Defense
** 29 September 1989
**
** References:
** 1) CCITT Recommendation G.711  (very difficult to follow)
** 2) "A New Digital Technique for Implementation of Any
**     Continuous PCM Companding Law," Villeret, Michel,
**     et al. 1973 IEEE Int. Conf. on Communications, Vol 1,
**     1973, pg. 11.12-11.17
** 3) MIL-STD-188-113,"Interoperability and Performance Standards
**     for Analog-to_Digital Conversion Techniques,"
**     17 February 1987
**
** Input: Signed 16 bit linear sample
** Output: 8 bit ulaw sample
*/

#define ZEROTRAP    /* turn on the trap as per the MIL-STD */
#undef ZEROTRAP
#define BIAS 0x84   /* define the add-in bias for 16 bit samples */
#define CLIP 32635

unsigned char linear2ulaw(sample) int sample; {
  static int exp_lut[256] = {0,0,1,1,2,2,2,2,3,3,3,3,3,3,3,3,
                             4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,
                             5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
                             5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
                             6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
                             6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
                             6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
                             6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
                             7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
                             7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
                             7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
                             7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
                             7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
                             7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
                             7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
                             7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7};
  int sign, exponent, mantissa;
  unsigned char ulawbyte;

  /* Get the sample into sign-magnitude. */
  sign = (sample >> 8) & 0x80;        /* set aside the sign */
  if(sign != 0) sample = -sample;        /* get magnitude */
  if(sample > CLIP) sample = CLIP;        /* clip the magnitude */

  /* Convert from 16 bit linear to ulaw. */
  sample = sample + BIAS;
  exponent = exp_lut[( sample >> 7 ) & 0xFF];
  mantissa = (sample >> (exponent + 3)) & 0x0F;
  ulawbyte = ~(sign | (exponent << 4) | mantissa);
#ifdef ZEROTRAP
  if (ulawbyte == 0) ulawbyte = 0x02;    /* optional CCITT trap */
#endif

  return(ulawbyte);
}

/*
** This routine converts from ulaw to 16 bit linear.
**
** Craig Reese: IDA/Supercomputing Research Center
** 29 September 1989
**
** References:
** 1) CCITT Recommendation G.711  (very difficult to follow)
** 2) MIL-STD-188-113,"Interoperability and Performance Standards
**     for Analog-to_Digital Conversion Techniques,"
**     17 February 1987
**
** Input: 8 bit ulaw sample
** Output: signed 16 bit linear sample
*/

int ulaw2linear(ulawbyte) unsigned char ulawbyte; {
  static int exp_lut[8] = { 0, 132, 396, 924, 1980, 4092, 8316, 16764 };
  int sign, exponent, mantissa, sample;

  ulawbyte = ~ulawbyte;
  sign = (ulawbyte & 0x80);
  exponent = (ulawbyte >> 4) & 0x07;
  mantissa = ulawbyte & 0x0F;
  sample = exp_lut[exponent] + (mantissa << (exponent + 3));
  if(sign != 0) sample = -sample;

  return(sample);
}



=======================================================================

PART 3 - Speech Coding and Compression

Q3.1: Speech compression techniques.

  [The FAQ for comp.compression includes a few questions and answers
   on the compression of speech.]

------------------------------------------------------------------------

Q3.2: What are some good references/books on coding/compression?

------------------------------------------------------------------------

Q3.3: What software is available?

A lossless compressor for speech signals is available by anonymous ftp from
svr-ftp.eng.cam.ac.uk in directory misc and file shorten-0.4.shar.  It will
compile and run on UNIX workstations and will cope with a wide variety of
formats.  Compression is typically 50% for 16bit clean speech sampled at
16kHz.

  [ADPCM, CELP and GSM source appear to be available by ftp - can someone
   provide details?]



=======================================================================

PART 4 - Speech Synthesis

Q4.1: What is speech synthesis?

Speech synthesis is the task of transforming written input to spoken output.
The input can either be provided in a graphemic/orthographic or a phonemic
script, depending on its source.

------------------------------------------------------------------------

Q4.2: How can speech synthesis be performed?

There are several algorithms.  The choice depends on the task they're used
for.  The easiest way is to just record the voice of a person speaking the
desired phrases.  This is useful if only a restricted volume of phrases and
sentences is used, e.g. messages in a train station, or schedule information
via phone.  The quality depends on the way recording is done.

More sophisticated but worse in quality are algorithms which split the
speech into smaller pieces.  The smaller those units are, the less are they
in number, but the quality also decreases.  An often used unit is the phoneme,
the smallest linguistic unit.  Depending on the language used there are about
35-50 phonemes in western European languages, i.e. there are 35-50 single
recordings. The problem is combining them as fluent speech requires fluent
transitions between the elements. The intellegibility is therefore lower, but
the memory required is small.

A solution to this dilemma is using diphones. Instead of splitting at the
transitions, the cut is done at the center of the phonemes, leaving the
transitions themselves intact. This gives about 400 elements (20*20) and
the quality increases.

The longer the units become, the more elements are there, but the quality
increases along with the memory required. Other units which are widely used
are half-syllables, syllables, words, or combinations of them, e.g. word stems
and inflectional endings.

------------------------------------------------------------------------

Q4.3: What are some good references/books on synthesis?

MITalk (also known as DECtalk) is one of the most sucessful speech synthesis
systems around.  It is described in:

    John Allen, Sharon Hunnicut and Dennis H. Klatt, "From Text to Speech:
    The MITalk System", Cambridge University Press, 1987.

------------------------------------------------------------------------

Q4.4: What software/hardware is available?

There appears to be very little Public Domain or Shareware speech synthesis
related software available for FTP.  However, the following are available.
Strictly speaking, not all the following sources are speech synthesis - all
are speech output systems.


SIMTEL-20
The following is a list of speech related software available from SIMTEL-20
and its mirror sites for PCs.

Directory PD1:<MSDOS.VOICE>
 Filename   Type Length   Date   Description
 ==============================================
 AUTOTALK.ARC  B   23618  881216  Digitized speech for the PC
 CVOICE.ARC    B   21335  891113  Tells time via voice response on PC
 HEARTYPE.ARC  B   10112  880422  Hear what you are typing, crude voice synth.
 HELPME2.ARC   B    8031  871130  Voice cries out 'Help Me!' from PC speaker
 SAY.ARC       B   20224  860330  Computer Speech - using phonemes
 SPEECH98.ZIP  B   41003  910628  Build speech (voice) on PC using 98 phonemes
 TALK.ARC      B    8576  861109  BASIC program to demo talking on a PC speaker
 TRAN.ARC      B   39766  890715  Repeats typed text in digital voice
 VDIGIT.ZIP    B  196284  901223  Toolkit: Add digitized voice to your programs
 VGREET.ARC    B   45281  900117  Voice says good morning/afternoon/evening


Other Sources

Package:     Text to phoneme program
Platform:    unknown
Description: Text to phoneme program.  Possibly based on Naval Research Lab's
         set of text to phoneme rules.
Availablity: By FTP from "shark.cse.fau.edu" (131.91.80.13) in the directory
        /pub/src/phon.tar.Z

Package:     Text to speech program
Platform:    Sun SPARC
Description: Text to speech program based on concatenation of pre-recorded
         speech segments.
Hardware:    SPARC audio I/O
Availablity: by FTP from "wilma.cs.brown.edu" as /pub/speak.tar.Z


Package:     xxx
Platform:    (PC, Mac, Sun, NeXt etc)
Rough Cost:  (if appropriate)
Description: (keep it brief)
Hardware:    (requirement list)
Availablity: (ftp info, email contact or company contact)


Can anyone provide information on the following packages?

    MacIntalk (Mac) - formant based speech synthesis
    Narrator (Amiga) - formant based synthesis
    Bliss software
    CSRE software
    JSRU software
    Klatt Software
    Sensimetrics products

Can anyone provide information on speech synthesis chip sets?

Please email or post suitable information for this list.  Commercial and
research packages are both appropriate.

[This list may be large enough to justify a separate posting]


=======================================================================

PART 5 - Speech Recognition

Q5.1: What is speech recognition?

Anyone got a good definition?

------------------------------------------------------------------------

Q5.2: How can I build a very simple speech recogniser?

Doug Danforth provides a detailed account in article 253 in the comp.speech
archives - also available as file info/DIY_Speech_Recognition.

The first part is reproduced here.

  QUICKY RECOGNIZER sketch:

  Here is a simple recognizer that should give you 85%+ recognition
  accuracy.  The accuracy is a function of WHAT words you have in
  your vocabulary.  Long distinct words are easy.  Short similar
  words are hard.  You can get 98+% on the digits with this recognizer.

  Overview:
  (1) Find the begining and end of the utterance.
  (2) Filter the raw signal into frequency bands.
  (3) Cut the utterance into a fixed number of segments.
  (4) Average data for each band in each segment.
  (5) Store this pattern with its name.
  (6) Collect training set of about 3 repetitions of each pattern (word).
  (7) Recognize unknown by comparing its pattern against all patterns
      in the training set and returning the name of the pattern closest
      to the unknown.

Many variations upon the theme can be made to improve the performance.
Try different filtering of the raw signal and different processing methods.

------------------------------------------------------------------------

Q5.2: What does speaker dependent/adaptive/independent mean?

A speaker dependent system is developed (trained) to operate for a single
speaker.  These systems are usually easier to develop, cheaper to buy and
more accurate, but are not as flexible as speaker adaptive or speaker
independent systems.

A speaker independent system is developed (trained) to operate for any
speaker or speakers of a particular type (e.g. male/female, American/English).
These systems are the most difficult to develop, most expensive and currently
accuracy is not as good.  They are the most flexible.

A speaker adaptive system is developed to adapt its operation for new
speakers that it encounters usually based on a general model of speaker
characteristics.  It lies somewhere between speaker independent and speaker
adaptive systems.

Each type of system is suited to different applications and domains.

------------------------------------------------------------------------

Q5.3: What does small/medium/large/very-large vocabulary mean?

The size of vocabulary of a speech recognition system affects the complexity,
processing requirements and the accuracy of the system.  Some applications
only require a few words (e.g. numbers only), others require very large
dictionaries (e.g. dictation machines).

There are no established definitions but the following may be a helpful guide.

    small vocabulary - tens of words
    medium vocabulary - hundreds of words
    large vocabulary - thousands of words
    very-large vocabulary - tens of thousands of words.

[Does anyone have a more precise definition?]

------------------------------------------------------------------------

Q5.4: What does continuous speech or isolated-word mean?

An isolated-word system operates on single words at a time - requiring a
pause between saying each word.  This is the simplest form of recognition
to perform, because the pronunciation of the words tends not affect each
other.  Because the occurrences of each particular word are similar they are
easier to recognise.

A continuous speech system operates on speech in which words are connected
together, i.e. not separated by pauses.  Continuous speech is more difficult
to handle because of a variety of effects.  One effect is "coarticulation" -
the production of each phoneme is affects by the production of surrounding
phonemes and the so the start and end of words are affected by the preceding
and following words.  The recognition of continuous speech is affected by
the rate of speech (fast speech tends to be harder).

------------------------------------------------------------------------

Q5.5: How is speech recognition done?

A wide variety of techniques are used to perform speech recognition.
There are many types of speech recognition.  There are many levels of
speech recognition/processing/understanding.

Typically speech recognition starts with the digital sampling of speech.
The next stage would be acoustic signal processing.  Common techniques
include a variety of spectral analyses, LPC analysis, the cepstral transform,
cochlea modelling and many, many more.

The next stage will typically try to recognise phonemes, groups of phonemes
or words.  This stage can be achieved by many processes such as DTW (Dynamic
Time Warping),  HMM (hidden Markov modelling), NNs (Neural Networks), and
sometimes expert systems.  In crude terms, all these processes to recognise
the patterns of speech.  The most advanced systems are statistically
motivated.

Some systems utilise knowledge of grammar to help with the recognition
process.

Some systems attempt to utilise prosody (pitch, stress, rhythm etc) to
process the speech input.

Some systems try to "understand" speech.  That is, they try to convert the
words into a representation of what the speaker intended to mean or achieve
by what they said.

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Q5.6: What are some good references/books on recognition?

Suggestions?

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Q5.7: What packages are available?

Package Name: xxx
Platform:     PC, Mac, UNIX, ....
Description:  (e.g. isolated word, speaker independent...)
Rough Cost:   (if applicable)
Requirements: (hardware/software needs - if applicable)
Misc:
Contact:      (email, ftp or address)


Can anyone provide info on

    DragonDictate
    SayIt (from Qualix)
    HTK (HMM Toolkit)
    Voice Navigator (from Articulate Systems)
    IN3 Voice Command
    Votan


I would like information on any software/hardware/packages that you know about.
Commercial, public domain and research packages are all appropriate.

[If there is enough information a separate posting could be started.]


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PART 6 - Speaker Recognition/Verification

Q6.1: What is speaker recognition/verification?

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Q6.2: Where is speaker recognition used?

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Q6.3: What are techniques for speaker recognition?

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Q6.4: How good is speaker recognition?

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Q6.5: What are some good references/books on speaker recognition?

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Q6.6: What packages are available?


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PART 7 - Natural Language Processing

There is a lot of useful information on the following questions in the
FAQ for comp.ai.  The FAQ lists available software and useful references.
Included is a substantial list of software, documentation and other info
which is available by ftp.

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Q7.1: What is NLP?

Natural Language Processing is a field of great breadth.  It covers everything
from syntax and semantic analysis or text, to methods of "understanding"
texts, to methods of generating text from abstract representations, to
language translations and more.

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Q7.2: What are some good references/books on NLP?

Any recommendations?  A few references/books for each area such as parsing,
translation, knowledge representation etc, would be suitable.

The FAQ for the "comp.ai" newsgroup includes some useful refs also.

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Q7.3: What software is available?

The FAQ for the "comp.ai" newsgroup lists a variety of language processing
software that is available.  That FAQ is posted monthly.

Natural Language Software Registry
The Natural Language Software Registry is available from the German Research
Institute for Artificial Intelligence (DFKI) in Saarbrucken.

The current version details
+ speech signal processors, e.g. Computerized Speech Lab (Kay Electronics)
+ morphological analyzers, e.g. PC-KIMMO (Summer Institute for Linguistics)
+ parsers, e.g. Alveytools (University of Edinburgh)
+ knowledge representation systems, e.g. Rhet (University of Rochester)
+ multicomponent systems, such as ELU (ISSCO), PENMAN (ISI), Pundit (UNISYS),
        SNePS (SUNY Buffalo),
+ applications programs (misc.)

This document is available on-line via anonymous ftp to ftp.dfki.uni-sb.de
(directory: registry; or: tira.uchicago.edu, IP 128.135.96.31), by email to
[e-mail].

If you have developed a piece of software for natural language
processing that other researchers might find useful, you can include
it by returning a description form, available from the same source.