background image
ISO/IEC 10918-1 : 1993(E)
SOI
EOI
TISO09 50-93/d 031
Compressed image data
[Tables/misc.]
DHP segment
Frame
1
Frame
last
Figure B.13 Syntax for the hierarchical mode of operation
Figure B.13 [D31], = 3 cm = 117.%
Hierarchical mode syntax requires a DHP marker segment that appears before the non-differential frame or frames. The
hierarchical mode compressed image data may include EXP marker segments and differential frames which shall follow
the initial non-differential frame. The frame structure in hierarchical mode is identical to the frame structure in non-
hierarchical mode.
The non-differential frames in the hierarchical sequence shall use one of the coding processes specified for SOF
n
markers:
SOF
0
, SOF
1
, SOF
2
, SOF
3
, SOF
9
, SOF
10
and SOF
11
. The differential frames shall use one of the processes specified for
SOF
5
, SOF
6
, SOF
7
, SOF
13
, SOF
14
and SOF
15
. The allowed combinations of SOF markers within one hierarchical
sequence are specified in Annex J.
The sample precision (P) shall be constant for all frames and have the identical value as that coded in the DHP marker
segment. The number of samples per line (X) for all frames shall not exceed the value coded in the DHP marker segment.
If the number of lines (Y) is non-zero in the DHP marker segment, then the number of lines for all frames shall not exceed
the value in the DHP marker segment.
B.3.2
DHP segment syntax
The DHP segment defines the image components, size, and sampling factors for the completed hierarchical sequence of
frames. The DHP segment shall precede the first frame; a single DHP segment shall occur in the compressed image data.
The DHP segment structure is identical to the frame header syntax, except that the DHP marker is used instead of the
SOF
n
marker. The figures and description of B.2.2 then apply, except that the quantization table destination selector
parameter shall be set to zero in the DHP segment.
B.3.3
EXP segment syntax
Figure B.14 specifies the marker segment structure for the EXP segment. The EXP segment shall be present if (and only
if) expansion of the reference components is required either horizontally or vertically. The EXP segment parameters apply
only to the next frame (which shall be a differential frame) in the image. If required, the EXP segment shall be one of the
table-specification segments or miscellaneous marker segments preceding the frame header; the EXP segment shall not be
one of the table-specification segments or miscellaneous marker segments preceding a scan header or a DHP marker
segment.
TISO0960-93/d032
EXP
Le
Eh Ev
Expand segment
Figure B.14 Syntax of the expand segment
Figure B.14 [D32], = 2.5 cm = 98.%
46
CCITT Rec. T.81 (1992 E)
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