Dialogic 6.2 manual Fax Infopkt Parameters

The Bfv API Functions

Fax Infopkt Parameters

The T.30 protocol requires two communicating fax machines to agree on several transmission parameters at the beginning of a facsimile transmission. These transmission parameters include the bit rate, scan time, coding scheme, and the basic document format parameters – vertical resolution, page width, and page length. The least capable fax machine determines the values of these parameters; both fax machines adjust to the final values.

Two infopkts:

INFOPKT_T30_PARAMETERS

INFOPKT_DOCUMENT_PARAMETERS

affect the parameters that are negotiated during the T.30 protocol handshaking procedure.

The INFOPKT_T30_PARAMETERS infopkt specifies the desired values of the transmission parameters. Normally the default values are used, but INFOPKT_T30_PARAMETERS is useful, for example, for setting a lower bit rate.

The INFOPKT_DOCUMENT_PARAMETERS infopkt sets the document related parameters: vertical resolution, length, and width (only the vertical resolution is programmable). These parameters format the fax data that is sent out on the phone line.

INFOPKT_DOCUMENT_PARAMETERS is required and specifies the desired resolution. If it appears in the midst of an infopkt stream, both machines might renegotiate to the new parameter values.

While document parameters define an entire fax document sent over the telephone line, page parameters define an entire page only, and strip parameters define horizontal strips of data within a page.

For ASCII data, there are page parameters and strip parameters. For G3 data, there are strip parameters. Because page formatting elements (top and bottom margins, etc.) are inherent in G3 data; there are no separate page parameters.

The INFOPKT_PAGE_PARAMETERS infopkt defines the ASCII page parameters, which apply only to pages. Its use is optional, and when it is not included with ASCII data infopkts, the module uses the default values (see Appendix E in Volume 6 of the Bfv API Reference Manual for default values).

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