ECE 4331, Fall, 2009. Zhu Han Department of Electrical and Computer Engineering Class 22 Nov. 6 th , 2009. Motivation – Image compression. What linear combination of 8x8 basis signals produces an 8x8 block in the image?. Learning Objectives. Introduction to the DCT and IDCT.
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Zhu Han
Department of Electrical and Computer Engineering
Class 22
Nov. 6th, 2009
What linear combination of 8x8 basis signals produces an 8x8 block in the image?

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(
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k = 0, 1, 2, …, N1.
and i = 0, 1, 2, …, N1.
small block
Zonal Coding: Coefficients outside the zone mask are zeroed.
Basic idea of Motion Compensation:
Motion Vectors
Block Matchinghow to find the matching block?
Search range:
Residuals
Table 1: MPEG1 Constraints
The six layers of MPEG video bit stream
X
Z
Available from earlier frame (X)
Available from later frame (Z)
Y
transmit
buffer
Variable
length
code
Frame
being
coded
DCT
Quantize
Inverse
DCT
Reference
frame
De
quantize
Reconstructing a reference frame that will be the same as at the decoderI P B B B P B B B P B B B
1 5 2 3 4 9 6 7 8 13 10 11 12
A typical group of pictures in coding order
I B B B P B B B P B B B P
CB
CR
0
1
4
5
2
3
Spatial sampling relationship for MPEG1
 Luminance sample
 Color difference sample
Coding of MacroblockJPEG quantization table(luminance)
MPEG quantization table(for intra coding)
Nonintra coding of macroblocks
controller
Scale
factor
Buffer
fullness
Variablelength
coder
IN
OUT
Frame
recorder
Inverse
DCT
Transmit
buffer
Quantize
DCT
DC
Prediction
Motion
predictor
De
quantize
Prediction
encoder
Reference
frame
Motion vectors
A Simplified MPEG encoder