Voice API Programming Guide — June 2005 117
Speed and Volume Control
The default volume modification table is shown in Table12.
Consider the following usage information on the volume modification table:
•Each entry in the table is a deviation in decibels from the starting point or volume (“origin”).
Each entry in the table is equivalent to 2dB from the origin. Volume can be decreased 2 dB by
specifying position 1 in the table, or by moving one step down. For example, the increase[1]
position (two steps from the origin) increases volume by 4 dB.
•The total volume modification range is from -20 dB to +10 dB. In this table, the highest
position utilized is the increase[4] position. The remaining increase fields are set to -128 (80h).
If these “non-adjustment” positions are selected, the default action is to play at the increase[4]
volume. These fields can be reset, as long as no values higher than +10 are used; for example,
you could spread the 10 dB volume increase over 10 steps rather than 5.
•In the volume modification table, the default entries for index values +6 to +10 are -128 which
represent a null-entry. To customize the table entries, you must use the dx_setsvmt() function.
•On DM3 boards, when adjustment is associated with a DTMF digit, volume can be increased
or decreased in increments of 1 (2 dB) only. To achieve an increase in volume of 6dB for
example, the user would press the DTMF digit three times.
Table12. Default Volume Modification Table
Table Entry Default Value (dB) Absolute Position
decrease[0] -20 -10
decrease[1] -18 -9
decrease[2] -16 -8
decrease[3] -14 -7
decrease[4] -12 -6
decrease[5] -10 -5
decrease[6] -08 -4
decrease[7] -06 -3
decrease[8] -04 -2
decrease[9] -02 -1
origin 0 0
increase[0] +02 1
increase[1] +04 2
increase[2] +06 3
increase[3] +08 4
increase[4] +10 5
increase[5] -128 (80h) 6
increase[6] -128 (80h) 7
increase[7] -128 (80h) 8
increase[8] -128 (80h) 9
increase[9] -128 (80h) 10