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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

header

page 1

header

page 1

data

page 2

header

page 2

data

... page n

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-API ignores 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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