Eicon Networks 206-412-06 ANNEX B (NORMATIVE): SFF FORMAT, Type, Comment, Parameter, COMMON-ISDN-API, B.1 Introduction, B.2 SFF coding rules, B.2.1 Document header

ANNEX B (NORMATIVE): SFF FORMAT

B.1 Introduction

SFF (Structured Fax File) is a representation specific to fax group 3 documents. As shown below in Fiugre 6 it consists of information concerning the page structure and compressed line data of the fax document. An SFF-formatted document always starts with a header, which is valid for the complete document. Every page starts with a page header. This is followed by the pixel information, line by line. As the SFF format is a file format specification, some entries in header structures (e.g. double-chaining of pages) may not be used or supported by COMMON-ISDN-API.

document	page 1	page 1	page 2	page 2	...	page n
header	header	data	header	data		data

Figure 6: SFF format

B.2 SFF coding rules

The following type conventions are used:

byte	8-bit unsigned
word	16-bit unsigned integer, least significant octet first
dword	32-bit unsigned integer, least significant word first

B.2.1 Document header

Parameter	Type	Comment
SFF_Id	dword	Magic value (identification) of SFF Format: coded as
		0x66666653 ("SFFF")
Version	byte	Version number of SFF document: coded 0x01
reserved	byte	Reserved for future extensions; coded 0x00
User Information	word	Manufacturer-specific user information (not used by COM-
		MON-ISDN-API, coded as 0x0000)
Page Count	word	Number of pages in the document. Must be coded 0x0000 if
		not known (as in the case of receiving a document).
OffsetFirstPageHeader	word	Byte offset of first page header from start of document
		header. This value is normally equal to the size of the docu-
		ment header (0x14), but there could be additional user-
		specific data between the document header and the first page
		header. COMMON-ISDN-APIignores and does not provide
		such additional data.
OffsetLastPageHeader	dword	Byte offset of last page header from start of document header.
		Must be coded 0x00000000 if not known (as in the case of
		receiving a document).
OffsetDocumentEnd	dword	Byte offset of document end from start of document header.
		Must be coded 0x00000000 if not known (as in the case of
		receiving a document).

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