Festival Speech Synthesis System: - Speech Resource Pages

Also if syllabification is required there is an opportunity to run a set of "letter-to-sound"-rules on the input (actually
an arbitrary re-write rule system). If the variable lex_lts_set is set, the lts ruleset of that name is applied to the
flat input before syllabification. This allows simple predictable changes such as conversion of final r into longer
vowel for English RP from American labelled lexicons.
A list of all matching entries in the addenda and the compiled lexicon may be found by the function
lex.lookup_all. This function takes a word and returns all matching entries irrespective of part of speech.
You can optionall intercept the words as they are lookup up, and after they have been found through pre_hooks
and post_hooks for each lexicon. This allows a function or list of functions to be applied to an word and feature
sbefore lookup or to the resulting entry after lookup. The following example shows how to add voice specific entries
to a general lexicon without affecting other voices that use that lexicon.
For example suppose we were trying to use a Scottish English voice with the US English (cmu) lexicon. A number of
entgries will be inapporpriate but we can redefine some entries thus
(set! cmu_us_awb::lexicon_addenda
'(
("edinburgh" n (((eh d) 1) ((ax n) 0) ((b r ax) 0)))
("poem" n (((p ow) 1) ((y ax m) 0)))
("usual" n (((y uw) 1) ((zh ax l) 0)))
("air" n (((ey r) 1)))
("hair" n (((hh ey r) 1)))
("fair" n (((f ey r) 1)))
("chair" n (((ch ey r) 1)))))
We can the define a function that chesk to see if the word looked up is in the speaker specific exception list and use
that entry instead.
(define (cmu_us_awb::cmu_lookup_post entry)
"(cmu_us_awb::cmu_lookup_post entry)
Speaker specific lexicon addeda."
(let ((ne
(assoc_string (car entry) cmu_us_awb::lexicon_addenda)))
(if ne
ne
entry)))
And then for the particualr voice set up we need to add both a selection part and a reset part. Thuis following the
FestVox vonventions for voice set up.
(define (cmu_us_awb::select_lexicon)
)
...
...
(lex.select "cmu")
;; Get old var for reset and to append our function to is
(set! cmu_us_awb::old_cmu_post_hooks
(lex.set.post_hooks nil))
(lex.set.post_hooks
(append cmu_us_awb::old_cmu_post_hooks
(list cmu_us_awb::cmu_lookup_post)))
...
(define (cmu_us_awb::reset_lexicon)
...
;; reset CMU's post_hooks back to original
(lex.set.post_hooks cmu_us_awb::old_cmu_post_hooks)
...