The basic building block for Festival is the utterance. The
structure consists of a set of relations over a set of
items. Each item represents a object such as a word, segment,
syllable, etc. while relations relate these items together. An item may
appear in multiple relations, such as a segment will be in a
Segment relation and also in the SylStructure relation.
Relations define an ordered structure over the items within them, in
general these may be arbitrary graphs but in practice so far we have
only used lists and trees Items may contain a number of
features.
There are no built-in relations in Festival and the names and use of
them is controlled by the particular modules used to do synthesis.
Language, voice and module specific relations can easy be created and
manipulated. However within our basic voices we have followed a number
of conventions that should be followed if you wish to use some of the
existing modules.
The relation names used will depend on the particular structure chosen
for your voice. So far most of our released voices have the same
basic structure though some of our research voices contain quite
a different set of relations. For our basic English voices the
relations used are as follows
- Text
Contains a single item which contains a feature with the input character
string that is being synthesized
- Token
A list of trees where each root of each tree is the white space
separated tokenized object from the input character string. Punctuation
and whitespace has been stripped and placed on features on these token
items. The daughters of each of these roots are the list of words
that the token is associated with. In many cases this is a one
to one relationship, but in general it is one to zero or
more. For example tokens comprising of digits will typically
be associated with a number of words.
- Word
The words in the utterance. By word we typically mean something
that can be given a pronunciation from a lexicon (or letter-to-sound
rules). However in most of our voices we distinguish pronunciation by
the words and a part of speech feature. Words with also be leaves of the
Token relation, leaves of the Phrase relation and roots of
the SylStructure relation.
- Phrase
A simple list of trees representing the prosodic phrasing on the
utterance. In our voices we only have one level of prosodic phrase
below the utterance (though you can easily add a deeper hierarchy
if your models require it). The tree roots are labeled with
the phrase type and the leaves of these trees are in the
Word relation.
- Syllable
A simple list of syllable items. These syllable items are intermediate
nodes in the SylStructure relation allowing access to the words
these syllables are in and the segments that are in these syllables.
In this format no further onset/coda distinction is made explicit but can
be derived from this information.
- Segment
A simple list of segment (phone) items. These form the leaves of
the SylStructure relation through which we can find where each
segment is placed within its syllable and word. By convention
silence phones do not appear in any syllable (or word) but will
exist in the segment relation.
- SylStructure
A list of tree structures over the items in the Word,
Syllable and Segment items.
- IntEvent
A simple list of intonation events (accents and boundaries).
These are related to syllables through the Intonation relation.
- Intonation
A list of trees whose roots are items in the Syllable relation,
and daughters are in the IntEvent relation. It is assumed that a
syllable may have a number of intonation events associated with it (at
least accents and boundaries), but an intonation event may only by
associated with one syllable.
- Wave
A relation consisting of a single item that has a feature with the
synthesized waveform.
- Target
A list of trees whose roots are segments and daughters are
F0 target points. This is only used by some intonation modules.
- Unit, SourceSegments, Frames, SourceCoef TargetCoef
A number of relations used the the UniSyn module.
