
71
μ
PD70433
16. CODEC INSTRUCTIONS
The V55PI has 9 codec instructions.
Using these special instructions on the V55PI enables not only image information MH encoding but also MR encoding
which previously required the use of a special device such as an ACEE (advanced compression/expansion engine) to be
implemented by means of a small-scale, high-speed codec.
16.1 FEATURES
The V55PI has the following 9 codec instructions (4 for compression, 5 for expansion):
Compression instructions
(1)
Change point table creation instruction: COLTRP
(2)
Data transmission instruction (transmission of EOL
*1
, FILL, RTC
*2
, etc.): ALBIT
(3)
MH encoding instruction: MHENC
(4)
MR encoding instruction: MRENC
Expansion instructions
(5)
EOL detection instruction: SCHEOL
(6)
1-bit (tag) detection instruction: GETBIT
(7)
MH decoding change point table creation instruction: MHDEC
(8)
MR decoding change point table creation instruction: MRDEC
(9)
Pixel data creation instruction: CNVTRP
MH/MR encoding and MH/MR decoding using these instructions are performed as shown in Figures 16-1 and
16-2.
* 1.
EOL: End Of Line
RTC: Return To Control
2.
Note
When compression/expansion processing is performed using the V55PI codec instructions, the following
should be specified as preconditions.
Compression/expansion is to be performed line by line.
Consideration must be given to task switching and interrupt generation during compression processing.
The number of bits processed per line must not be changed during processing of one page.
The segment value must be changed for data over 64 Kbytes that straddles segments during processing.