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ISO/IEC 10918-1 : 1993(E)
The additional logic to interpret these various markers is contained in the box labeled "Interpret markers". DHT markers
shall be interpreted by processes using Huffman coding. DAC markers shall be interpreted by processes using arithmetic
coding. DQT markers shall be interpreted by DCT-based decoders. DRI markers shall be interpreted by all decoders.
APPn and COM markers shall be interpreted only to the extent that they do not interfere with the decoding.
By definition, the procedures in "Interpret markers" leave the system at the next marker. Note that if the expected SOI
marker is missing at the start of the compressed image data, an error condition has occurred. The techniques for detecting
and managing error conditions can be as elaborate or as simple as desired.
E.2.2
Control procedure for decoding a frame
Figure E.7 shows the control procedure for the decoding of a frame.
TISO1290-93/d067
Decode_frame
Interpret markers
Decode_scan
Done
Yes
No
Yes
No
Interpret frame header
SOS marker
?
EOI marker
?
Figure E.7 Control procedure for decoding a frame
Figure E.7 [D67], = 13.5 cm = 528.%
The loop is terminated if the EOI marker is found at the end of the scan.
The markers recognized by "Interpret markers" are listed in Table E.1. Subclause E.2.1 describes the extent to which the
various markers shall be interpreted.
CCITT Rec. T.81 (1992 E)
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