adv611 Analog Devices, Inc., adv611 Datasheet - Page 8

• Manufacturer Part Number: adv611
• Description: Closed Circuit Tv Digital Video Codec
• Manufacturer: Analog Devices, Inc.

ADV611/ADV612
THE PROGRAMMABLE QUANTIZER
This block quantizes the filtered image based on the response
profile of the human visual system. In general, the human eye
cannot resolve high frequencies in images to the same level of
accuracy as lower frequencies. Through intelligent “quantiza-
tion” of information contained within the filtered image, the
ADV611/ADV612 achieves compression without compromising
the visual quality of the image. Figure 9 shows the encode and
decode data formats used by the quantizer.
Figure 10 shows how a typical quantization pattern applies over
Mallat block data. The high frequency blocks receive much
larger quantization (appear darker) than the low frequency
blocks (appear lighter). Looking at this figure, one sees some key
point concerning quantization: (1) quantization relates directly
to frequency in Mallat block data and (2) levels of quantization
range widely from high to low frequency block. (Note that the
fill is based on a log formula.) The relation between actual
ADV611/ADV612 bin width factors and the Mallat block fill
pattern in Figure 10 appears in Table III.
40
37
38
41
28
29
36
39
34
31
32
35
19
20
27
25
22
33
30
26
23
18
10
11
16
13
17
14
24
21
9
Figure 10. Typical Quantization of Mallat Data Blocks (Graphed)
Cr COMPONENT
Cb COMPONENT
7
4
8
5
12
15
6
3
1
2
Y COMPONENT
–8–
LOW
WAVELET
NUMBER
15.0 BIN
DATA
Figure 9. Programmable Quantizer Data Flow
9.7
QUANTIZATION OF MALLAT BLOCKS
SIGNED
SIGNED
8.8 BW
1/BW
6.10
UNSIGNED
UNSIGNED
QUANTIZER - ENCODE MODE
1/BW
QUANTIZER - DECODE MODE
BW
SIGNED
SIGNED
0
15.17 DATA
WAVELET DATA
DE-QUANTIZED
23.8
0.5
TRNC
SAT
HIGH
15.0 BIN
NUMBER
9.7
WAVELET
DATA
REV. 0