Dialogic COMMON-ISDN-API Справочное руководство - Страница 8

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A
B (N
NNEX
ORMATIVE
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
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
SFF_Id
Version
reserved
User Information
Page Count
OffsetFirstPageHeader
OffsetLastPageHeader
OffsetDocumentEnd
): SFF F
ORMAT
page 1
page 1
header
data
Figure 6: SFF format
Type
Comment
dword
Magic value (identification) of SFF Format: coded as
0x66666653 ("SFFF")
byte
Version number of SFF document: coded 0x01
byte
Reserved for future extensions; coded 0x00
word
Manufacturer-specific user information (not used by COM-
MON-ISDN-API, coded as 0x0000)
word
Number of pages in the document. Must be coded 0x0000 if
not known (as in the case of receiving a document).
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.
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).
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).
page 2
page 2
header
data
...
page n
data
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