NSAM266SA Datasheet, PDF (27/52 Pages) National Semiconductor (TI) – NSAM266SA CompactSPEECHTM Digital Speech Processor with Serial Flash Interface

2 0 Software (Continued)
2 9 SPEECH SYNTHESIS
Speech synthesis is the technology that is used to create
messages out of predefined words and phrases stored in a
vocabulary
There are two kinds of predefined messages fixed mes-
sages (e g voice menus in a voice-mail system) and pro-
grammable messages (e g time and day stamp or the You
have n messages announcement in a DAM)
A vocabulary includes a set of predefined words and phras-
es needed to synthesize messages in any language Appli-
cations which support more than one language require a
separate vocabulary for each language
2 9 1 International Vocabulary Support (IVS)
IVS is a mechanism by which the CompactSPEECH proces-
sor can use several vocabularies stored on an external stor-
age device IVS enables CompactSPEECH to synthesize
messages with the same meaning but in different lan-
guages from separate vocabularies
Among IVS features
 Multiple vocabularies are stored on a single storage de-
vice
 Plug-and-play The same microcontroller code is used for
all languages
 Synthesized and recorded messages use the same voice
compression algorithm to achieve equal quality
 Argumented sentences (For example You have ^kn ^l
messages )
 Auto-synthesized time-and-day stamp (driven by the
CompactSPEECH’s clock)
 Support for various language and sentence structures
One versus many (for example You have one
message vs You have two messages)
None versus many (for example You have no mes-
sages vs You have two messages)
Number synthesis (English–Eighty vs French–
Quatre-vingt )
Word order (English–Twenty one vs German–Ein-
undzwanzig )
Days of the week (Monday through Sunday vs
Sunday through Saturday)
2 9 2 Vocabulary Design
There are several issues sometimes conflicting which must
be addressed when designing a vocabulary
Vocabulary If memory space is not an issue the vocabu-
content
lary could contain all the required sentences
each recorded separately
If memory space is a concern the vocabulary
must be compact it should contain the mini-
mum set of words and phrases required to
synthesize all the sentences The least mem-
ory is used when phrases and words that are
common to more than one sentence are re-
corded only once and the IVS tool is used to
synthesize sentences out of them
A good combination of sentence quality and
memory space is achieved if you take the
‘‘compact’’ approach and extend it to solve
pronunciation problems For example the
word twenty is pronounced differently when
used in the sentences You have twenty mes-
sages and You have twenty two messages
To solve this problem words that are pro-
nounced differently should be recorded more
than once each in the correct pronunciation
Vocabulary
recording
When recording vocabulary words there is a
compromise between space and quality On
one hand the words should be recorded and
saved in a compressed form and you would
like to use the best voice compression for that
purpose On the other hand the higher the
compression rate the worse the voice quality
Another issue to consider is the difference in
voice quality between synthesized and re-
corded messages (e g between time-and-
day stamp and incoming messages (ICMs) in
a DAM environment) It is more pleasant to
the human ear to hear them both in the same
quality
Vocabulary Sometimes compactness and high quality are
access
not enough There should be a simple and
flexible interface to access the vocabulary el-
ements Not only the vocabulary but also the
code to access it should be compact
When designing for a multi-lingual environ-
ment there are more issues to consider
Each vocabulary should be able to handle
language-specific structures and designed in
a cooperative way with the other vocabularies
so that the code to access each vocabulary is
the same When you use the command to
synthesize the sentence Monday 12 30 PM
you should not care in what language it is go-
ing to be played back
2 9 3 IVS Vocabulary Components
This section describes the basic concept of an IVS vocabu-
lary its components and the relationships between them
The basic
concepts
An IVS vocabulary consists of words sen-
tences and special codes that control the
behavior of the algorithm which Compact-
SPEECH uses to synthesize sentences
The word
table
The words are the basic units in the vocab-
ulary You create synthesized sentences
by combining words in the vocabulary
Each word in the vocabulary is given an
index which identifies it in the word table
Note that depending on the language
structures and sentences that you wish to
synthesize you may need to record some
words more than once in the vocabulary
For example if you synthesize the sen-
tences you have twenty messages and
you have twenty five messages the word
twenty is pronounced differently They
should therefore be defined as two differ-
ent words
The number The number tables allow you to treat num-
tables
bers differently depending on the context
Example 1 The number 1 can be an-
nounced as one as in mes-
sage number one or as first as
in first message
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