Voice Software Reference: Programmer's Guide: Voice Channel Parameters

6.3.1. Driver Buffer Usage Guidelines

6.3. Voice Channel Parameters

The voice channel parameter defines have a "DXCH_" prefix. All time units are in 10 ms unless otherwise noted.

The channel parameter defines, default settings, read/write privileges, and descriptions follow.

Table 5. Voice Channel Parameters

Define

Bytes

Read/
Write

Default

Description

DXCH_AUDIOLINEIN

Enable or disable the ProLine/2V audio jack line-in on voice channel 2

DXCH_CALLID

disabled

Enable or disable Caller ID for the channel as specified in dx_setparm( )
DX_CALLIDDISABLE

DXCH_DFLAGS

2

R/W

0

DTMF detection edge select

DXCH_DTINITSET

2

R/W

0

Specifies which DTMF digits to initiate play on. Values of different DTMF digits may be ORed together to form the bit mask. Possible values are listed below:

Value

DTMF Digit

-DM_1

1

-DM_2

2

-DM_3

3

-DM_4

4

-DM_5

5

-DM_6

6

-DM_7

7

-DM_8

8

-DM_9

9

-DM_0

0

-DM_S

*

-DM_P

#

-DM_A

a

-DM_B

b

-DM_C

c

-DM_D

d

DXCH_DTMFDEB

2

R/W

0

DTMF debounce time (record delay- minimum time for DTMF to be present to be considered valid. Used to remove false DTMF signals during recording. Increase the value for less sensitivity to DTMF.

DXCH_DTMFTLK

2

R/W

5

Sets the minimum time for DTMF to be present during playback to be considered valid. Increasing the value provides more immunity to talk-off/playoff.
Set to -1 to disable.

DXCH_MAXRWINK

1

R/W

20

Maximum Loop Current for Wink - The maximum time that loop current needs to be on before recognizing a wink (10 ms units)

DXCH_MFMODE

2

R/W

2

This is a word-length bit mask that selects the minimum length of KP tones to be detected. The possible values of this field are:
0 - detect KP tone > 40 ms
2 - detect KP tone > 65 ms

If the value is set to 2, any KP tone greater than 65ms will be returned to the application during MF detection. This ensures that only standard-length KP tones (100ms) are detected. If set to 0 (zero), any KP tone longer than 40ms will be detected.

DXCH_MINRWINK

1

R/W

10

Minimum Loop Current for Wink - The minimum time that loop current needs to be on before recognizing a wink (10 ms units)

DXCH_NUMRXBUFFERS

4

R/W

2

Changes the number of record buffers used. Before you can use DXCH_NUMRXBUFFERS, you must set DXCH_VARNUMBUFFERS to 1 and specify the size of the record buffer in DXCH_RXDATABUFSIZE. This value can be 2 or greater.

DXCH_NUMTXBUFFERS

4

R/W

2

Sets the number of play buffers. Before you can use DXCH_NUMTXBUFFERS, you must set DXCH_VARNUMBUFFERS to 1 and specify the size of the play buffer in DXCH_TXDATABUFSIZE. This value can be 2 or greater.

DXCH_PLAYDRATE

2

R/W

6000

Play Digitization Rate - This parameter sets the digitization rate of the voice data that is played on this channel. Voice Data can be played at 6k or 8k sampling rates (voice data must be played at the same rate it was recorded at). Valid parameter values are:
6000 - 6K sampling rate
8000 - 8k sampling rate

DXCH_RECRDRATE

2

R/W

6000

Record Digitization Rate - This parameter sets the rate at which the recorded voice data is digitized. Voice Data can be digitized at 6k or 8k sampling rates. Valid values are:
6000 - 6K sampling rate
8000 - 8k sampling rate

DXCH_RINGCNT

2

R/W

4

Number of rings to wait before returning a ring event.

DXCH_RXDATABUFSIZE

4

R/W

32K

Sets the size of the record buffers only that are used to transfer data (e.g., ADSI data) between the application on the host and the driver to control buffering delay. The buffer is used by the dx_RxIottData( ) and dx_TxRxIottData( ) functions. The minimum buffer size is 128 bytes. The largest available buffer size is 32KB (must be in multiples of 128). If play and record buffers are the same size, use DXCH_XFERBUFSIZE.

DXCH_T_IDD

2

R/W

5

DTMF Interdigit delay (time between digits in DTMF dialing)

DXCH_TTDATA

1

R/W

10

DTMF length (duration) for dialing.

DXCH_TXDATABUFSIZE

4

R/W

32K

Sets the size of the play buffers only that are used to transfer data between the application on the host and the driver. The minimum buffer size is 128 bytes. The largest available buffer size is 32KB (must be in multiples of 128). If play and record buffers are the same size, use DXCH_XFERBUFSIZE.

DXCH_VARNUMBUFFERS

4

R/W

0

Allows you to use more than two play or record buffers when set to 1. This parameter is used in conjunction with DXCH_XFERBUFSIZE, DXCH_RXDATABUFSIZE, DXCH_TXDATABUFSIZE, DXCH_NUMRXBUFFERS and DXCH_NUMTXBUFFERS. Valid parameter values are:
1 (True) - more than 2 buffers
0 (False) - 2 buffers

DXCH_WINKDLY

1

R/W

15

Wink Delay - The delay after a ring is received before issuing a wink (10 ms units)

DXCH_WINKLEN

1

R/W

15

Wink Length - The duration of a wink in the off-hook state (10 ms units)

DXCH_XFERBUFSIZE

4

R/W

32K

This parameter sets the size of both the play and record buffers used to transfer data

between the application on the host and the driver. These buffers are also called driver buffers. The minimum buffer size is 128 bytes. The largest available buffer size is 32KB (must be in multiples of 128).This parm can be used with the dx_getparm( ) function. The dx_setchxfercnt( ) function sets the bulk queue buffer size for the channel. This function can change the size of the buffer used to transfer voice data between a user application and the Dialogic hardware. The dx_setchxfercnt( ) function allows a smaller driver data transfer buffer size. The minimum buffer size is now 1KB. The largest available buffer size is 32KB. In general, this function is used in conjunction with the User I/O feature; for more information, see the dx_setuio( ) function. This function sets up the frequency with which the application-registered read or write functions are called by the voice dll. For applications requiring more frequent access to voice data in smaller chunks, you can use this function on a per channel basis to lower the buffer size.

6.3.1. Driver Buffer Usage Guidelines

The total memory available for record buffers is 64 KB. The default number of buffers is 2 and the default size of each buffer is 32 KB. The default value for DXCH_VARNUMBUFFERS is 0.

There are three possible scenarios for changing these defaults:

Change the buffer size only and use all other defaults.
Change the buffer size only and have the system automatically reproportion the number of buffers to use the entire buffer space.
Change the buffer size and control the number of buffers used.

In the first scenario, let's say you change the buffer size to 4 KB, the following values are used:

DXCH_RXDATABUFSIZE (or DXCH_TXDATABUFSIZE) = 4
DXCH_VARNUMBUFFERS = 0 (default value)
number of buffers used is 2 (default value)

In the second scenario, using a buffer size of 4 KB, the system automatically allocates the number of buffers using the lesser of: (a) 32 or (b) 64 KB divided by the desired buffer size:

DXCH_RXDATABUFSIZE (or DXCH_TXDATABUFSIZE) = 4
DXCH_VARNUMBUFFERS = 1 (True)
number of buffers used is 16 (64 divided by 4 is 16; that is, the maximum number of buffers in the 64 KB space is used)

In the third scenario, using a buffer size of 4 KB, you specify the number of buffers to be 4, for example. In this case, only 16 KB of total available memory is used for the buffers; 48 KB of space is unused:

DXCH_RXDATABUFSIZE (or DXCH_TXDATABUFSIZE) = 4
DXCH_VARNUMBUFFERS = 1 (True)
DXCH_NUMRXBUFFERS (or DXCH_NUMTXBUFFERS) = 4

Note that the number of buffers multiplied by the buffer size cannot exceed 64 KB.

The driver buffer size must be at least 2 times the size of the firmware buffer size. If it isn't, play/record may terminate abruptly and data loss may occur.

The default firmware buffer size is 512; therefore, the driver buffer size must be at least 1024 bytes. If you modify the driver buffer size to be less than 1024, you must adjust the firmware buffer sizes in the voice.prm to be less than 512.

NOTES:: 1. In automatic speech recognition (ASR) applications that use Continuous Speech Processing (CSP), the driver buffer size must be at least 3 times the size of the firmware buffer size. Thus, if the firmware buffer size is 512, the driver buffer size must be at least 1536.

2. The DXBD_TXBUFSIZE and DXBD_RXBUFSIZE parameters in dx_setparm( ) cannot be used to modify the firmware buffer size. The only way to modify the firmware buffer size is to edit the voice.prm parameter file.

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