Digital Signal Processing Reference
In-Depth Information
(a)
(b)
(c)
(d)
FIGURE 9.10
Microview of the block-DCT-encoded
IKONOS
1-m satellite picture with 8
8 pixel blocks, to
show the reduction in the number of constraints available for enhancing a digital image as its bit
rate is decreased. (a) Original satellite picture coded at 0.43 bpp. (b) Block-DCT coding at 0.264
bpp. (c) Block-DCT coding at 0.15 bpp. (d) Block-DCT coding, in which only the DC (lowest fre-
quency) discrete cosine transform coefficient is retained from each 8
×
8 frequency square. Note
that this last case is identical to the downsampled
IKONOS
image with an effective GSD of 8 m.
×
in order to constrain the solution to the observed data present in the refer-
ence frame or field.
H
(
k
)
is not an estimate in this case, because displacement
vectors are not required to downsample and/or subsample
x
. The parameter
λ
(
i
)
represents the confidence in estimating
H
(
i
)
, constructed using the sub-
pixel displacements estimated from
y
(
i
)
with respect to
y
(
k
)
through the appli-
cation of block matching. If only a single, progressively scanned video frame
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