114 Voice API Programming Guide — June 2005
Speed and Volume Control
dx_addvoldig( )
adds a digit that will modify volume by a specified amount
See the Voice API Library Reference for detailed information about these functions.
9.3 Speed and Volume Adjustment Functions
Speed or volume can be adjusted explicitly or can be set to adjust in response to a preset condition,
such as a specific digit. For example, speed could be set to increase a certain amount when “1” is
pressed on the telephone keypad. The functions used for speed and volume adjustment are:
dx_setsvcond()
Sets conditions that adjust speed or volume. Use this function to adjust speed or volume in
response to a DTMF digit or start of play.
dx_adjsv( )
Adjusts speed or volume explicitly. Use this function if your adjustment condition is not a digit
or start of play. For example, the application could call this function after detecting a spoken
word (voice recognition) or a certain key on the keyboard.
See the Voice API Library Reference for detailed information about these functions.
9.4 Speed and Volume Modification Tables
Each channel has a speed or volume modification table for play speed or play volume adjustments.
Except for the value of the settings, the table is the same for speed and volume.
Each speed or volume modification table (SVMT) table has 21 entries, 20 that allow for a
maximum of 10 increases and decreases in speed or volume. The entry in the middle of the table is
referred to as the “origin” entry that represents normal speed or volume. The normal speed or
volume is how playback occurs when the speed and volume control feature is not used. See
Table11, “Default Speed Modification Table”, on page 116 and Table 12, “Default Volume
Modification Table”, on page117.
The origin, or normal speed or volume, is the basis for all settings in the table. Typically, the origin
is set to 0. Speed and volume increases or decreases by moving up or down the tables. Other entries
in the table specify a speed or volume setting in terms of a deviation from normal. For example, if a
speed modification table (SMT) entry is -10, this value represents a 10% decrease from the normal
speed.
Although the origin is typically set to normal speed/volume, changing the setting of the origin does
not affect the other settings, because all values in the SVMT are based on a deviation from normal
speed/volume.
Speed and volume control adjustments are specified by moving the current speed/volume pointer in
the table to another SVMT table entry; this translates to increasing or decreasing the current
speed/volume to the value specified in the table entry.