(p7) the Jpeg2000 Still Image Coding System

8/8/2019 (p7) the Jpeg2000 Still Image Coding System

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Outline

Advantages of JPEG2000

Block diagrams of the JPEG2000

Wavelet Transform

Coding

Region of Interests (ROI)

Comparative results


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Advantages of JPEG2000

JPEG

JPEGDCTHuffman

JPEG

(ROI)

JPEG2000


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JPEG at 0.125 bpp (enlarged)


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JPEG2000 at 0.125 bpp


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Block diagrams of the HPEG2000

Forward

Transform Quantization

Entropy

Encoding

Source

Image Data

Compressed

Image Data

Inverse

TransformDequantization

Entropy

Decoding

Compressed

Image Data

ReconstructedImage Data

Store or

Transmit


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Block diagrams of encode

Wavelet

TransformQuantization


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tiling

tile(SSWT)

tile

RGBp YCbCr


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R

G

B

DC level

shifting

DC level

shifting

DC level

shifting

Color

Transformation

C1

C2

C3

JPEG2000

encoding

JPEG2000

encoding

JPEG2000

encoding

Color

image

Compressed

Image Data


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Tile


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RGBm YCbCr


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RGBm YCbCr

RGB YCbCr


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Wavelet Transform


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Wavelet Transform Example

(5, 3) filter:

h0[n] = (-1 2 6 2 -1)/8 g0[n] = (1 2 1)/2

h1[n] = (-1 2 -1)/2 g1[n] = (-1 -2 6 -2 -1)/8

input: 100, 100, 100, 100, 200, 200, 200, 200,

:100, 100, 100, 100, 100, 100, 200, 200, 200, 200,

: 100 100 87.5 112.5 187.5 212.5 200 200: 0 0 0 -50 50 0 0 0

:: 100 100 106.5 112.5 162.5 212.5 206.25 200: 0 0 -6.25 -12.5 37.5 -12.5 -6.25 0: 100 100 100 100 200 200 200 200

(-100+200+600+400-200)/8


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2D Separate DWT


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L H

LL

HL

LH

HH

Image in

spatial

domain

HL

LH

HHHL

LH

HH

2D Separate DWT


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Coding

Based on bit-plane

Three passes

Significant Propagation Pass Magnitude Refinement Pass

Cleanup Pass


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BIT PLANES

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2N-1

2N-2

MSB

LSB


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Bit-plane Coding


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Scanning Order & Neighbor

D0 V0 D1

V1 X V2

D2 V3 D3


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About Significance state

Each coefficient in a code-block has an

associated binary state variable called its

significance state.

Significance states are initialized to 0

(coefficient is insignificant) and may

become 1 (coefficient is significant) during

the course of the coding of the code-block.


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Significant Propagation Pass

The significance propagation pass includes only bits ofcoefficients that were insignificant (the significance bithas yet to be encountered) and have a non-zero context.

All other coefficients are skipped.

The context is delivered to the arithmetic decoder (alongwith the bit stream) and the decoded coefficient bit isreturned.

If the value of this bit is 1 then the significance state isset to 1 and the immediate next bit to be decoded is thesign bit for the coefficient. Otherwise, the significance

state remains 0. When the contexts of successive coefficients and coding

passes are considered, the most current significancestate for this coefficient is used.


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Magnitude Refinement

The magnitude refinement pass includes the bits fromcoefficients that are already significant (except those thathave just become significant in the immediatelyproceeding significance propagation pass).

The context used is determined by the summation of thesignificance state of the horizontal, vertical, and diagonalneighbors. These are the states as currently known tothe decoder, not the states used before the significancedecoding pass.

Further, it is dependent on whether this is the firstrefinement bit (the bit immediately after the significanceand sign bits) or not.


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Cleanup Pass

All bits not encoded during the previous

passes (i.e. coefficients that are

insignificant and had the context value of

zero during the significance propagation

pass).

Use both neighbor context as in significant

propagation pass and run-length coding.


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Region of Interests Coding (ROI)

An ROI is a part of an image that is coded

earlier in the code stream than the rest of

the image (the background).

The method used is the Maxshift method.

ROI allows certain parts of the image to be

coded in better quality


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Examples of ROI


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0.125bpp

0.0625bpp


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ROI Mask


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Scaling of ROI coefficients


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MAXSHIFT


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Advantages of Maxshift method

Support for arbitrary shaped ROIs withminimal complexity

No need to send shape information No need for shape encoder and decoder

No need for ROI mask at decoder side

Decoder as simple as non-ROI capabledecoder


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Comparative results

(p7) the Jpeg2000 Still Image Coding System

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