ISO/IEC 10918-1 : 1993(E)
The marker and parameters shown in Figure B.14 are defined below. The size and allowed values of each parameter are
given in Table B.11.
EXP:
Expand reference components marker Marks the beginning of the expand reference components
segment.
Le:
Expand reference components segment length Specifies the length of the expand reference components
segment (see B.1.1.4).
Eh:
Expand horizontally If one, the reference components shall be expanded horizontally by a factor of two.
If horizontal expansion is not required, the value shall be zero.
Ev:
Expand vertically If one, the reference components shall be expanded vertically by a factor of two.
If vertical expansion is not required, the value shall be zero.
Both Eh and Ev shall be one if expansion is required both horizontally and vertically.
Table B.11 Expand segment parameter sizes and values
Values
Parameter
Size (bits)
Sequential DCT
Progressive DCT
Lossless
Baseline
Extended
Le
16
3
,1
Eh
1
4
0, 1
Ev
1
4
0, 1
B.4
Abbreviated format for compressed image data
Figure B.2 shows the high-level constituent parts of the interchange format. This format includes all table specifications
required for decoding. If an application environment provides methods for table specification other than by means of the
compressed image data, some or all of the table specifications may be omitted. Compressed image data which is missing
any table specification data required for decoding has the abbreviated format.
B.5
Abbreviated format for table-specification data
Figure B.2 shows the high-level constituent parts of the interchange format. If no frames are present in the compressed
image data, the only purpose of the compressed image data is to convey table specifications or miscellaneous marker
segments defined in B.2.4.1, B.2.4.2, B.2.4.5, and B.2.4.6. In this case the compressed image data has the abbreviated
format for table specification data (see Figure B.15).
TISO0970-93/d033
SOI
EOI
Compressed image data
[Tables/misc.]
Figure B.15 Abbreviated format for table-specification data syntax
Figure B.15 [D33], = 3 cm = 117.% dim. à 100
B.6
Summary
The order of the constituent parts of interchange format and all marker segment structures is summarized in Figures B.16
and B.17. Note that in Figure B.16 double-lined boxes enclose marker segments. In Figures B.16 and B.17 thick-lined
boxes enclose only markers.
The EXP segment can be mixed with the other tables/miscellaneous marker segments preceding the frame header but not
with the tables/miscellaneous marker segments preceding the DHP segment or the scan header.
CCITT Rec. T.81 (1992 E)
47