Databases Reference
In-Depth Information
in the previous pass, we replace them with
:
6
1 3
10
−7
7
6
4
4 −4
4 −3
2 −2 −2
0
The first coefficient we encounter has a value of 6. This is less than the threshold value of
8; however, the descendants of this coefficient include coefficients with values of 13 and 10.
Therefore, this coefficient cannot be classified as a zerotree root. This is an example of what
we defined as an isolated zero. The next two coefficients in the scan are
−
7 and 7. Both of
these coefficients have magnitudes less than the threshold value of 8. Furthermore, all of their
descendants also have magnitudes less than 8. Therefore, these two coefficients are coded as
zr
. The next two elements in the scan are 13 and 10, which are both coded as
sp
. The final
two elements in the scan are 6 and 4. These are both less than the threshold, but they do not
have any descendants. We code these coefficients as
iz
. Thus, this dominant pass is coded as
iz zr zr sp sp iz iz
which requires 14 bits, bringing the total number of bits used to 23. The significant coefficients
are reconstructed with values 1
.
5
T
1
=
12. Thus, the reconstruction at this point is
28
0
12
12
0
0
0
0
0000
0000
We add the new significant coefficients to the subordinate list:
L
S
={
26
,
13
,
10
}
In the subordinate pass, we take the difference between the coefficients and their recon-
structions and quantize these to obtain the correction or refinement values for these coefficients.
The possible values for the correction terms are
±
T
1
/
4
=±
2:
−
=−
⇒
=−
26
28
2
Correction term
2
−
=
⇒
=
(3)
13
12
1
Correction term
2
10
−
12
=−
2
⇒
Correction term
=−
2
