adv601lc Analog Devices, Inc., adv601lc Datasheet - Page 4

• Manufacturer Part Number: adv601lc
• Description: Ultralow Cost Video Codec
• Manufacturer: Analog Devices, Inc.

ADV601LC
THE WAVELET KERNEL
This block contains a set of filters and decimators that work on
the image in both horizontal and vertical directions. Figure 6
illustrates the filter tree structure. The filters apply carefully
chosen wavelet basis functions that better correlate to the broad-
band nature of images than the sinusoidal waves used in Dis-
crete Cosine Transform (DCT) compression schemes (JPEG,
MPEG, and H261).
An advantage of wavelet-based compression is that the entire
image can be filtered without being broken into sub-blocks as
required in DCT compression schemes. This full image filtering
eliminates the block artifacts seen in DCT compression and
offers more graceful image degradation at high compression
ratios. The availability of full image sub-band data also makes
image processing, scaling, and a number of other system fea-
tures possible with little or no computational overhead.
The resultant filtered image is made up of components of the
original image as is shown in Figure 3 (a modified Mallat Tree).
Note that Figure 3 shows how a component of video would be
filtered, but in multiple component video luminance and color
components are filtered separately. In Figure 4 and Figure 5 an
actual image and the Mallat Tree (luminance only) equivalent is
shown. It is important to note that while the image has been
filtered or transformed into the frequency domain, no compres-
sion has occurred. With the image in its filtered state, it is now
ready for processing in the second block, the quantizer.
BLOCK A IS HIGH PASS IN X AND DECIMATED BY TWO.
BLOCK B IS HIGH PASS IN X, HIGH PASS IN Y, AND DECIMATED BY EIGHT.
BLOCK C IS HIGH PASS IN X, LOW PASS IN Y, AND DECIMATED BY EIGHT.
BLOCK D IS LOW PASS IN X, HIGH PASS IN Y, AND DECIMATED BY EIGHT.
BLOCK E IS HIGH PASS IN X, HIGH PASS IN Y, AND DECIMATED BY 32.
BLOCK F IS HIGH PASS IN X, LOW PASS IN Y, AND DECIMATED BY 32.
BLOCK G IS LOW PASS IN X, HIGH PASS IN Y, AND DECIMATED BY 32.
M
N
J
K
L
G
Figure 3. Modified Mallat Diagram (Block Letters Correspond to Those in Filter Tree)
H
I
D
F
E
C
B
–4–
BLOCK H IS HIGH PASS IN X, HIGH PASS IN Y, AND DECIMATED BY 128.
BLOCK I IS HIGH PASS IN X, LOW PASS IN Y, AND DECIMATED BY 128.
BLOCK J IS LOW PASS IN X, HIGH PASS IN Y, AND DECIMATED BY 128.
BLOCK K IS HIGH PASS IN X, HIGH PASS IN Y, AND DECIMATED BY 512.
BLOCK L IS HIGH PASS IN X, LOW PASS IN Y, AND DECIMATED BY 512.
BLOCK M IS LOW PASS IN X, HIGH PASS IN Y, AND DECIMATED BY 512.
BLOCK N IS LOW PASS IN X, LOW PASS IN Y, AND DECIMATED BY 512.
Understanding the structure and function of the wavelet filters
and resultant product is the key to obtaining the highest perfor-
mance from the ADV601LC. Consider the following points:
• The data in all blocks (except N) for all components are high
• The data in most blocks is more likely to contain zeros or
• The human visual system is less sensitive to higher frequency
• Attenuation of the selected blocks in luminance or color com-
• High quality filtered/decimated images can be extracted/created
Through leverage of these key points, the ADV601LC not
only compresses video, but offers a host of application features.
Please see the Applying the ADV601LC section for details on
getting the most out of the ADV601LC’s sub-band coding
architecture in different applications.
pass filtered. Therefore, the mean pixel value in those blocks
is typically zero and a histogram of the pixel values in these
blocks will contain a single “hump” (Laplacian distribution).
strings of zeros than unfiltered image data.
blocks than low ones.
ponents results in control over sharpness, brightness, contrast
and saturation.
without computational overhead.
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