ADV611 Просмотр технического описания (PDF) - Analog Devices

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ADV611

Closed Circuit TV Digital Video Codec

Analog Devices 

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.

9.7

WAVELET

DATA

QUANTIZER - ENCODE MODE

15.17 DATA

SIGNED SIGNED

UNSIGNED

6.10

0.5

1/BW

1/BW

TRNC

15.0 BIN

NUMBER

15.0 BIN

NUMBER

QUANTIZER - DECODE MODE

SIGNED SIGNED

23.8

DE-QUANTIZED

WAVELET DATA

SAT

UNSIGNED

8.8 BW

BW

9.7

WAVELET

DATA

Figure 9. Programmable Quantizer Data Flow

39 33 24

36 30

15

27

21

18

12

Y COMPONENT

6

0

9

3

40 34

37 31

25

16

28 22

19

13

10

Cb COMPONENT

7

1

4

41 35

38 32

26

17

29 23

20

14

11

Cr COMPONENT

8

2

5

QUANTIZATION OF MALLAT BLOCKS

LOW

HIGH

Figure 10. Typical Quantization of Mallat Data Blocks (Graphed)

–8–

REV. 0

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