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ADV601

–7–

REV. 0

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

ADV601 achieves compression without compromising the visual

quality of the image. Figure 7 shows the encode and decode

data formats used by the quantizer.

Figure 8 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 ADV601 bin width factors

and the Mallat block fill pattern in Figure 8 appears in Table II.

9.7

WAVELET

DATA

6.10 1/BW

15.17 DATA

0.5

15.0 BIN

NUMBER

QUANTIZER - ENCODE MODE

TRNC

SIGNED

UNSIGNED

1/BW

QUANTIZER - DECODE MODE

8.8 BW

23.8 DE-QUANTIZED

WAVELET DATA

9.7

WAVELET

DATA

15.0 BIN

NUMBER

SIGNED

UNSIGNED

SAT

Figure 7. Programmable Quantizer Data Flow

Y COMPONENT

Cb COMPONENT

Cr COMPONENT

LOW

HIGH

QUANTIZATION OF MALLAT BLOCKS

Figure 8. Typical Quantization of Mallat Data Blocks (Graphed)

ADV601JS 数据表(PDF) 7 Page - Analog Devices

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