• 5.11.1. DX_SVCB Overview
• 5.11.2. DX_SVCB Definition
• 5.11.3. DX_SVCB Parameters
• 5.11.4. Example of Setting a DTMF Digit To Adjust Playback Volume

5.11. DX_SVCB: Speed/Volume Adjustment Condition Block

The DX_SVCB data structure contains parameters for the Speed/Volum Adjustment Condition Block.

5.11.1. DX_SVCB Overview

This strucutre is used by dx_setsvcond( ) function to specify a play adjustment condition that is added to the internal Speed and Volume Condition Table (SVCT). The play adjustment conditions in the SVCT are used to adjust speed or volume automatically at the beginning of playback or in response to digits entered by the user during playback.

The dx_setsvcond( ), dx_addspddig( ), and dx_addvoldig( ) functions can be used to add play adjustment conditions to the SVCT. These functions tie a speed or volume adjustment to an external event, such as a DTMF digit.

You cannot change an existing speed or volume adjustment condition in the SVCT without using the dx_clrsvcond( ) function to clear the SVCT of all conditions and then adding a new set of adjustment conditions to the SVCT.

This structure is used to specify the following:

• table type (Speed Modification Table, Volume Modification Table)
• adjustment type (step, index, toggle)
• adjustment size or action
• adjustment condition (incoming digit, beginning of play)
• level/edge sensitivity for incoming digits

NOTE:

To reset or remove any DX_SVCB adjustment condition blocks, you must clear all the speed/volume adjustment conditions using dx_clrsvcond( ).

5.11.2. DX_SVCB Definition

The typedef for the structure is as follows:

    typedef struct DX_SVCB {

       unsigned short type;      /* Bit Mask */

       short adjsize;            /* Adjustment Size */

       unsigned char digit;      /* ASCII digit value that causes the action */

       unsigned char digtype;    /* Digit Type (e.g., 0 = DTMF) */

    } DX_SVCB;




5.11.3. DX_SVCB Parameters

Parameter	Description
type	Type of Playback Adjustment: Specifies an OR combination of the following:   Adjustment Table Type (required): specifies one adjustment type, either speed or volume   Adjustment Method (required): specifies one adjustment method (step, index, or toggle), which also determines how the adjsize value is used   Options: specifies one or no options (level/edge digit detection, or automatic adjustment for beginning of next playback)
	Table Type	Description
	SV_SPEEDTBL	selects speed table
	SV_VOLUMETBL	selects volume table
	Adjustment Method	Description
	SV_ABSPOS	Index: Sets adjsize field to use an absolute adjustment position (index) in the Speed or Volume Modification Table. The index value can be from -10 to +10, based on position 0, the origin, or center, of the table.
	SV_RELCURPOS	Step: Sets adjsize field to use a number of steps by which to adjust the speed or volume. The number of steps is relative to the current position in the table. Specify the adjustment in a positive or negative number of steps to increase or decrease the current speed or volume. For example, specify -2 to lower the speed or volume by 2 steps in the Speed or Volume Modification Table.
	SV_TOGGLE	Toggle: Sets adjsize field to use one of the toggle defines, which control the values for the current and last-modified speed and volume settings and allow you to toggle the speed or volume between standard (the origin) and any setting selected by the user.
	Options	Description
	SV_LEVEL	Level: Sets the digit adjustment condition to be level sensitive. At the start of play, existing digits in the digit buffer will be checked to see if they are level-sensitive play adjustment digits. If the first digit in the buffer is a level-sensitive play adjustment digit, it will cause a play adjustment and be removed from the buffer. Subsequent digits in the buffer will be treated the same way until the first occurrence of any digit that is not an SV_LEVEL play adjustment digit. If SV_LEVEL is not specified, the digit adjustment condition is edge sensitive; Existing edge-sensitive play adjustment digits in the digit buffer will not cause a play adjustment; but after the playback starts, edge-sensitive digits will cause a play adjustment.
	SV_BEGINPLAY	Automatic: Sets the play adjustment to occur automatically at the beginning of the next playback. This sets a speed or volume level without using a digit condition. The digit and digtype fields are ignored.
adjsize	Adjustment Size: Specifies the adjustment size. The valid values follow according to the adjustment method:   Step (SV_RELCURPOS)   Index (SV_ABSPOS)   Toggle Method (SV_TOGGLE)
	Step Values	Description
	+/- integer	a positive or negative integer representing the number of steps to adjust the level relative to the current setting in the SVMT.
	Index Values	Description
	-10 to +10 (integer)	an integer from -10 to +10 representing an absolute position in the SVMT.
	Toggle Methods	Description
	SV_TOGORIGIN	Sets the digit to toggle between the origin and the last modified speed or volume level (for example, between the -5 and 0 levels).
	SV_CURORIGIN	Resets the current speed or volume level to the origin (same effect as SV_ABSPOS with adjsize 0).
	SV_CURLASTMOD	Sets the current speed or volume to the last modified speed volume level (swaps the current and last-modified settings).
	SV_RESETORIG	Resets the current speed or volume to the origin and the last modified speed or volume to the origin.
digit	Digit: Specifies an ASCII digit that will adjust the play: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, a, b, c, d, #, *
digtype	Digit Type: Specifies the type of digit:
	DG_DTMF	DTMF digits

5.11.4. Example of Setting a DTMF Digit To Adjust Playback Volume

The following DX_SVCB structure is set to decrease the volume by one step whenever the DTMF digit 1 is detected:

    svcb[0].type    = SV_VOLUMETBL | SV_RELCURPOS;  
    svcb[0].adjsize = - 1;  
    svcb[0].digit    = '1';  
    svcb[0].digtype    = DG_DTMF;

The following DX_SVCB structure will set the playback speed to the value in the Speed Modification Table position 5 whenever the DTMF digit 2 is detected:

    svcb[0].type    = SV_SPEEDTBL | SV_ABSPOS;  
    svcb[0].adjsize = 5;  
    svcb[0].digit    = '2';  
    svcb[0].digtype    = DG_DTMF;

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