AN2121 Freescale Semiconductor / Motorola, AN2121 Datasheet - Page 13

• Manufacturer Part Number: AN2121
• Description: JPEG2000 Arithmetic Encoding on StarCore SC140
• Manufacturer: Freescale Semiconductor / Motorola

2.3.1
The encoding steps for the BAC can be summarized as follows:
The new interval becomes [C, C+A) with subintervals [C, C+(A Q
The following paragraphs describe the application of these steps to the first three symbols in the example.
Initialization
C = 0.01
0.01
0
1. Initialize A
2. Determine the event values (MPS:True or MPS:False), code register C, Q
3. Update the code word and/or interval depending on the event values
If MPS:True:T
a) Update the code word to point at the lower bound of the interval
b) Update the interval width
If MPS:False: F Leave the code word as it is already pointing to the lower bound
a) Update the interval width
C = 0 and A = 1.0.
16
3
4
3
F (occurs)
BAC Encoding
C = C + (Q
A = A – (Q
A = Q
1
4
0.000011
F
0.0011
Q
1
4
1
4
F
e
0.01
= 3
= 3
e
0
16
64
= 1 and C
A
e
e
0.0111
C = 0.010011
C = 0.01
A)
A)
Freescale Semiconductor, Inc.
For More Information On This Product,
0
= 0
Go to: www.freescale.com
Figure 5. BAC Process
Background Theory
16
3
4
3
T (occurs)
3
4
0.001001
T (occurs)
0.1001
P
3
4
3
4
T
e
0.11
= 9
= 9
e
16
64
)) and [C+(A Q
Binary Arithmetic Coding
e
, and P
e
), C+A)
e
.
0.0111
1
1
9