Festival Speech Synthesis System: - Speech Resource Pages

EST_Utterance *u = get_c_utt(utt);
EST_Item *s;
float end=0.0, dur;
LISP ph_avgs,ldur;
We cannot list the average durations for each phone in the source code as we cannot tell which phoneset we are using
(or what modifications we want to make to durations between speakers). Therefore the phone and average duration
information is held in a Scheme variable for easy setting at run time. To use the information in our C++ domain we
must get that value from the Scheme domain. This is done with the following statement.
ph_avgs = siod_get_lval("phoneme_averages","no phoneme durations");
The first argument to siod_get_lval is the Scheme name of a variable which has been set to an assoc list of
phone and average duration before this module is called. See the variable phone_durations in
`lib/mrpa_durs.scm' for the format. The second argument to siod_get_lval. is an error message to be
printed if the variable phone_averages is not set. If the second argument to siod_get_lval is NULL then no
error is given and if the variable is unset this function simply returns the Scheme value nil.
Now that we have the duration data we can go through each segment in the utterance and add the duration. The loop
looks like
for (s=u->relation("Segment")->head(); s != 0; s = next(s))
{
We can lookup the average duration of the current segment name using the function siod_assoc_str. As
arguments, it takes the segment name s->name() and the assoc list of phones and duration.
ldur = siod_assoc_str(s->name(),ph_avgs);
Note the return value is actually a LISP pair (phone name and duration), or nil if the phone isn't in the list. Here we
check if the segment is in the list. If it is not we print an error and set the duration to 100 ms, if it is in the list the
floating point number is extracted from the LISP pair.
if (ldur == NIL)
{
cerr