Databases Reference
In-Depth Information
...
SOC
0xFF4F
SOT
Tile 1
markers
SOD
Tile
Part 1
SOT
Tile
Part n
EOC
OxFFD9
Main
0xFF90
0xFF93
0xFF90
F I GU R E 16 . 22
Organization of codestream [
219
].
that generates an embedded bitstream. Each packet contains the binary codestream for each
code-block within a precinct, thus enabling a very high level of spatial random access. The
context of the packet is provided in the packet header and the packet is indexed by layer,
resolution, precinct, and component. The packets are combined into a
layer
that contains
contributions from all code-blocks in a tile.
The bitstream is organized using two-byte markers with the first byte being 0xFF. There
are six kinds of markers: delimiting markers, fixed information markers, functional markers,
pointer markers, in bitstream markers, and informational markers. Some of the markers are
followed by segments that contain the parameters corresponding to the marker.
DelimitingMarkers
The codestream is bracketed by the start of codestream (SOC) marker,
which is the first marker in the main header and the end of codestream (EOC) marker, which
terminates the codestream. The codestream can contain several tiles with each tile header
bracketed by the start of tile-part (SOT) marker followed by the SOT marker segment, and
the start of data (SOD) marker. The SOD marker separates the header from the data. This
organization is shown in Figure
16.22
.
Fixed Information Marker
The fixed information marker provides required information
about the image. There is only one such marker, is the image and tile size marker (SIZ).
The segment following this marker contains information about the uncompressed image. The
information contained in this segment and its organization is as follows:
Parameter
Size (bytes) Description
SIZ
2
Marker (0xFF51)
Lsiz
2
Length of segment in bytes
Rsiz
2
Xsiz
4
Width of reference grid
Ysiz
4
Height of reference grid
XOsiz
4
Horizontal offset from grid origin to left of image area
YOsiz
4
Vertical offset from grid origin to top of image area
XTsiz
4
Width of one reference tile with respect to grid
YTsiz
4
Height of one reference tile with respect to grid
XTOsiz
4
Horizontal offset from grid origin to left side of first tile
YTOsiz
4
Vertical offset from grid origin to top side of first tile
Csiz
2
Number of components in the image
Ssiz
i
1
Precision in bits and sign of the
i
th component
XRSiz
i
1
Horizontal separation of
i
th component with respect to grid
YRSiz
i
1
Vertical separation of
i
th component with respect to grid
