ISO/IEC 10918-1 : 1993(E)
E.2.4
Control procedure for decoding a restart interval
The procedure for decoding a restart interval is shown in Figure E.9. The "Reset_decoder" procedure consists at least of
the following:
a)
if arithmetic coding is used, initialize the arithmetic decoder using the "Initdec" procedure described
in D.2.7;
b)
for DCT-based processes, set the DC prediction (PRED) to zero for all components in the scan
(see F.2.1.3.1);
c)
for lossless process, reset the prediction to a default value for all components in the scan (see H.2.1);
d)
do all other implementation-dependent setups that may be necessary.
TISO1310-93/d069
Reset_decoder
Decode_MCU
Find marker
Done
Yes
No
Decode_restart_
interval
More MCU
?
Figure E.9 Control procedure for decoding a restart interval
Figure E.9 [D69], = 12 cm = 469.%
At the end of the restart interval, the next marker is located. If a problem is detected in locating this marker, error handlin g
procedures may be invoked. While such procedures are optional, the decoder shall be able to correctly recognize restart
markers in the compressed data and reset the decoder when they are encountered. The decoder shall also be able to
recognize the DNL marker, set the number of lines defined in the DNL segment, and end the "Decode_restart_interval"
procedure.
NOTE The final restart interval may be smaller than the size specified by the DRI marker segment, as it includes only the
number of MCUs remaining in the scan.
CCITT Rec. T.81 (1992 E)
85