Mapping configuration for the speech/audio parameters.
All parameters except text
can be either:
If a function is used, it should return the desired value for
the speech parameter. The function is called for each speech
event to be played, and receives a context object parameter with
time
, and potentially point
and value
depending on the
track. point
is available if the audio event is related to a
data point, and value
is available if the track is used for a
context track using valueInterval
.