Databases Reference
In-Depth Information
0
0
0
1
0
0
0
0
0
0
0
1
1
0
0
0
0
0
0
0
0
1
0
0
0 0
0
0
0
0
0
0 0 0 0 0
F I GU R E 16 . 17
The most significant bitplane of the example stripe of coefficients
in Figure
16.16
.
as a 0 in this context. For the next coefficient,
2, which again results
in a zero-coding context of ZC6. The coefficient is insignificant so we encode it as a zero in
the ZC6 context. For the next coefficient
σ
h
=
1
,σ
v
=
0, and
σ
d
=
σ
h
=
,σ
v
=
σ
d
=
1. As this coefficient
is also insignificant, we encode a 0 in the ZC6 context. The next column does not have any
neighbors that are known to be significant; therefore, we switch to the run-length mode. As
all coefficients in the column are insignificant, we encode a 0 in the run-length context. The
same is true for the following three columns which brings us to the end of the stripe.
We now begin encoding the next bitplane. This is shown in Figure
16.18
.
The coefficients that have been declared significant in the previous pass are marked with
darker boxes. As we have some significant coefficients to work off of, we will go through each
of the three passes. In the first pass, the significance propagation pass, we only examine those
coefficients that have neighbors already declared to be significant. The first such coefficient
is the first coefficient in the second column. This coefficient has a diagonal neighbor, which
is significant. In order to encode this bit, we first determine the zero-coding context as all
bits in the significance propagation pass are encoded in the zero-coding mode. For this bit
σ
h
=
1
0, and
1. Using Table
16.3
, we obtain the context as ZC1. As the bit is not
significant, we encode a 0 in the ZC1 context. For the next bit,
0
,σ
v
=
0, and
σ
d
=
0.
This corresponds to a zero-coding context of ZC5. We encode a 0 in the ZC5 context. The
next bit is also insignificant with
σ
h
=
1
,σ
v
=
0, and
σ
d
=
1; therefore, we encode a 0 in the
ZC1 context. The last bit in the column does not have any known significant neighbors so we
skip over it.
σ
h
=
0
,σ
v
=
0, and
σ
d
=
