Information Technology Reference
In-Depth Information
Fig. 1(a) shows CI with the junction of scene changes. It is easy to find that the
inverses of CI are consistent with the PSNR curve.
(a)
CI and 1/CI of 'Mother and Daughter'
sequence
(b)
PSNR results for 'Mother and Daughter'
sequence
Fig. 1.
CI, 1/ CI and PSNR for 'Mother and Daughter' sequence (
ζ
=1/6)
3.2 Improved Buffer Allocation Scheme
CI is a simple and accurate measure of frame complexity and importance. Therefore,
it can provide a mechanism to control estimation of the target bit. If the frames' CIs
are large, it should allocate more remaining bits and buffer resource to them. From
Eq.(4), it can be concluded that
T
ref
(
n
j
) is directly with CI. Meanwhile, a frame with
large CI should take more buffer resource. From Eq.(3), if we want to allocate more
buffer resource to a frame, should enlarge
Tbl
(
n
j
). From Eq.(2b), if we want to large
Tbl
(
n
j
), we should reduce
D
deltp
. For computational simplicity, the improved buffer
allocation scheme is presented to adjust the allocation of remaining bits and buffer
resource by
Tn
Tn=CI
R
()
(12)
r
i, j
()
ref
j
(1)
j-
PN
Tbl n
()
- B /
8
C
σ
(13)
D
=
2
s
×
deltp
N-
1
p
where
is a constant range from 0.4 to 0.6. It is noted that the parameters used in the
above function all come from empirical experiments with different resolution and-
frame rate. The objective of this improvement is to save bits from those frames with
relatively less complexity or less importance and allocate more bits to frames with
higher complexity or more importance. The final target bits
R
for the new P-frame can
be calculated using equation (5), where
σ
increases to 0.55 from 0.5 so that
T
ref
has
β
more weight than
T
buf
.
4 Experimental Results and Analyses
To evaluate performances of the proposed method, rate control experiments are
implemented on QCIF video sequences with different activity and motion features.
Search WWH ::
Custom Search