Voice API Programming Guide — June 2005 113
9
9.Speed and Volume Control
This chapter describes how to control the speed and volume of play on a channel. The following
topics are discussed:
•Speed and Volume Control Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
•Speed and Volume Convenience Functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
•Speed and Volume Adjustment Functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
•Speed and Volume Modification Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
•Play Adjustment Digits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
•Setting Play Adjustment Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
•Explicitly Adjusting Speed and Volume . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
9.1 Speed and Volume Control Overview
The voice software contains functions and data structures to control the speed and volume of play
on a channel. This allows an end user to control the speed or volume of a message by entering a
DTMF tone, for example.
On DM3 boards, speed can be controlled on playbacks using the following encoding methods:
•OKI ADPCM 32 kbps
•G.711 PCM A-law or mu-law encoding 64 kbps
•linear PCM 64 kbps and 128 kbps
On Springware boards, speed can be controlled on playbacks using 24 kbps or 32 kbps ADPCM
only.
Volume can be controlled on all playbacks regardless of the encoding algorithm. For a list of
supported encoding methods, see Section 8.5, “Voice Encoding Methods”, on page89.
9.2 Speed and Volume Convenience Functions
The convenience functions set a digit that will adjust speed or volume, but do not use any data
structures. These convenience functions will only function properly if you use the default settings
of the speed or volume modification tables. These functions assume that the modification tables
have not been modified. The convenience functions are:
dx_addspddig( )
adds a digit that will modify speed by a specified amount