Post on 01-Jan-2016
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An Efficient Method for DCT-Domain Image Resizing with Mixed Field/Frame-Mode Macroblocks
Changhoon Yim and Michael A. Isnardi
IEEE TRANSACTION ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY, VOL. 9, NO. 5, AUGUST 1999
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Outline
Introduction DCT-Domain Image Resizing Decomposition of DCT-Domain Image
Resizing Operation Proposed DCT-Domain Image Resizing
Method Discussion on DCT-Domain Filtering Experimental Result Conclusion
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Introduction
Many image and video compression standards such as JPEG, MPEG-1, MPEG-2, and H.261 are based on DCT coding techniques.
In MPEG-2, there are field and frame pictures to accommodate coding of progressive and interlaced video.
Previous DCT-domain image resizing methods assume that all macroblocks are in the frame mode.
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DCT-Domain Image Resizing : Four Steps Low-pass filtering in the DCT domain Inverse DCT 2 : 1 downsampling Forward DCT
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DCT-Domain Image Resizing : Matrices
WC
CCST
1
1
0
0
1616:
168:
88:
W
S
C
01
01
01
018 IS
DCT transform matrix
Downsampling matrix
Low-pass filter
00
042
IIW
tTXTY
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Decomposition of DCT-Domain Image Resizing Operation
tt
t
t
CSC
CWXW
C
CCSY
0
0
0
0
ts
tcs
wt
t
c
w
CCXY
SSXX
C
CX
C
CX
WXWX
0
0
0
0
WW
CCt
t
1
0000
00
0000
00
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Inverse DCT for a DCT block
jijit
tt
tt
wt
t
w
XCXC
CXCCXC
CXCCXC
C
CX
C
C
XX
XXX
,,
1,10,1
1,00,0
1,10.1
1,00,0
of IDCT thesreprestent
0
0
0
0
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Discussion on DCT-Domain Filtering (1) Previous methods are simple low-pass filtering by tr
uncation in DCT domain The matrix is not equivalent to sharp low-pass filter i
n DFT domain, and dose not correspond to a liner convolution in the spatial domain
May produce visible aliasing and blocking artifacts Affect differently the field- and frame-mode in spatial
domain may result in serious blocking artifacts between field- and frame-mode macroblocks
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Discussion on DCT-Domain Filtering (2) The implicit low-pass filtering operation as av
eraging by the downsampling matrices would be a good compromise for block-based DCT-domain image resizing
Would not have any blocking artifact The filtering characteristics should be the sa
me for field- and frame-mode macroblocks