Rate-distortion Optimized Mode Selection Based on Multi-path Channel Simulation

1
Rate-distortion Optimized Mode Selection Based on
Multi-path Channel Simulation

• Markus Gärtner
• Davide Bertozzi
• Project Proposal
• Classroom Presentation
• 6th February 2001

2
Overview

• Hybrid Video Coding
• Mode selection
• Previous works
• Multi-path channel simulation
• Architecture
• Distortion Measure
• Expected Results
• Workplan

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Motion-compensated hybrid coder
Intraframe DCT coder
IntraframeDecoder
Motion compensated predictor
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Inter- / Intra-frame coding

• P Frame (inter)
• low bit rate, exploits temporal redundancy
• sensitivity to error propagation
• I Frame (intra)
• high bit rate, no temporal dependency
• stops error propagation

I Frame
P Frame
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Optimal Mode Selection
Intra
Foreman
30
20
Salesman
10
2
4
6
Packet error rate
Source Färber, Stuhlmüller, Girod ICIP 1999
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Previous Approaches

• Feedback based methods
• Transmission delay limits applicability
• Heuristic refresh frequency periodic
  intra-coding of
• Whole frames (Turletti-Huitema)
• Random blocks (Coté-Kossentini)
• Threshold methods (Liao-Villasenor,
  Färber-Steinbach-Girod)
• Content adaptive methods (Haskell-Messerschmitt)
• Rate-distortion optimization (Coté-Kossentini)

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Block-weighted Distortion Estimate
Coté-Kossentini

• Block mode chosen according to
• Error propagation only beyond one frame
• Distortion measure as simple sum of Dq and Dc

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Recursive optimal per-pixel Estimate
Zhang-Reghunatan-Rose

• Distortion is calculated for each pixel
• Computational complexity
• Holds for inter-pel accuracy only

SNR Miss America Grandma Salesman Mother Daughter Carphone Foreman
ROPE 37.8 dB 35.4 dB 33.6 dB 32.8 dB 29.9 dB 26.7 dB
BWDE 37.2 dB 34.2 dB 31.6 dB 30.7 dB 28.1 dB 25.0 dB
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Our Approach
Coder
Decoder
Channel 1
Distortion Estimate Mode Selection
Channel 2
Decoder
Decoder
Channel n
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H.263 Coding Standard
frame
16x16 macroblock
8x8 block
GOB

• I-frame DCT coding of each 8x8 block
• P-frame DPCM, 8x8 DCT coding of error, one
  motion vector per macroblock
• Mode selection on macro-block basis

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Channel Model

• Model on macro-block basis

X
Channel 1
X
Channel 2
X
Controlled Randomness
Channel n
X
X
Group of blocks
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Distortion Measure
R
where
Our approach
D

• di comprises any distortion incurred by path i

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Expected Results
Average PSNR at decoder
Channel modelling
Cote-Kossentini
H. 263
Error probability
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Workplan
Final presentation
Performance measurements
Implementation of Channel models
Setup of H.263
Literature Investigation
Week 1
Week 2
Week 3
Week 4
Week 5