Fast motion estimation and mode decision for h 264 video coding in packet loss environment
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Presenter : SeungDae Jeong. Fast motion estimation and mode decision for H.264 video coding in packet loss environment. Li Liu, Xinhua Zhuang Computer Science Department, University of Missouri-Columbia, USA IEEE ICME(International Conference on Multimedia & Expo) 2008 June 2008.

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Fast motion estimation and mode decision for h 264 video coding in packet loss environment

Presenter : SeungDae Jeong

Fast motion estimation and mode decisionfor H.264 video coding in packet loss environment

Li Liu, Xinhua Zhuang

Computer Science Department, University of Missouri-Columbia, USA

IEEE ICME(International Conference on Multimedia & Expo) 2008

June 2008


Introduction
Introduction

  • Packet loss environment

    • Practical video communications

    • Videos are usually coded without considering varying channel conditions

    • Error propagation


Introduction1
Introduction

Intra frame

Previous frame

Inter frame

with packet loss

  • “Intra refresh” algorithm

    • Using intra frames that doesn't refer to previous frames

  • The decision of intra mode

    • Rate distortion optimization

      • Quantization distortion

      • Channel distortion

        • Simulation based estimation

        • Model based estimation


Contents
Contents

  • RD Optimized intra fresh for error resilience

    • Lagrange Cost Function in Packet Loss Environment

    • Model Based Channel Distortion Estimation

  • Use channel distortion map for fast mode decision and motion estimation

  • Channel distortion map based fast mode decision and motion estimation algorithm

    • Fast Mode Decision

    • Fast Motion Estimation

  • Experiment results

  • Conclusion


Lagrange cost function in packet loss environment
Lagrange Cost Function in Packet Loss Environment

The source distortion by quantization

The result bit rate

The relation between distortion and bit rate

Set of all defined coding options for macroblock m in frame n


Lagrange cost function in packet loss environment1
Lagrange Cost Function in Packet Loss Environment

The estimated channel packet loss rate

The quantization distortion

The error propagation distortion

if reference frames in motion estimation are erroneous

The error concealment distortion

when a macrobloak is lost

In packet loss environment


Lagrange cost function in packet loss environment2
Lagrange Cost Function in Packet Loss Environment

The modified Lagrange cost function for RD optimization mode decision

The rate distortion cost for intra mode


Model based channel distortion estimation
Model Based Channel Distortion Estimation

  • Define a channel distortion map on 4x4 block basis

    • To track potential error propagation


Model based channel distortion estimation1
Model Based Channel Distortion Estimation

The optimal mode decision

The error propagation distortion of ith block

The error concealment distortion

The estimated error propagation distortion

Block based channel distortion map


Use channel distortion map for fast mode decision and motion estimation
Use channel distortion map for fast mode decision and motion estimation

  • The error propagation distortion tends to surpass the quantization distortion as

    • frames contain more motions (e.g., from frame 150 to 250)

    • loss rate increases (e.g., from 0.05 to 0.10)


Use channel distortion map for fast mode decision and motion estimation1
Use channel distortion map for fast mode decision and motion estimation

  • Statistical information from coded video sequence using original MBDE algorithm


Channel distortion map based fast mode decision and motion estimation algorithm
Channel distortion map basedfast mode decision and motion estimation algorithm

  • Fast mode decision

    • Computational cost of estimating Dep(o) is quite small

    • By using Dep(o) as assistance to decide early termination of possible inter coding choices, encoding speed can be accelerated significantly

    • Fast Motion Estimation

    • Choosing the best motion vector

    • Minimizing a Lagrange cost function


Fast mode decision
Fast mode decision

  • Computational cost

    • Inter coding cost > Intra coding cost

  • The calculation of minDep

    • Dependent on optimal motion vector decision from motion estimation process

    • Computational cost can not be reduced

  • Computing Dep(o) based on the predicted motion vector


Fast mode decision1
Fast mode decision

Computing Dep(o) based on the predicted motion vector


Fast motion estimation
Fast motion estimation

The sum of absolute difference

The number of bits to code motion information

  • Minimizing a Lagrange cost function

    • Fast motion estimation algorithm selects best motion vector from a set of candidates, and terminates those macroblocks that may have large error propagation distortion associated



Experiment results
Experiment results

  • Implemented using H.264 reference software JM12.1

    • http://iphome.hhi.de/suehting/tml/download/old_jm/

  • Video sequences

    • Carphone, Foreman, Coastguard

    • QCIF format, 7.5 fps

    • Fixed quantization parameter (QP)

  • Packet loss simulation

    • S. Wenger, “Internet Error Patterns”


Experiment results1
Experiment results

  • PSNR

    • Peak Signal-to-Noise Ratio

  • Bit rate

  • Speed

    • Very fast


Conclusion
Conclusion

Two stage fast mode decision and motion estimation algorithm for H.264 video coding in packet loss environment

Advantage of estimated channel distortion as assistance to decide early termination of possible inter coding options

Reduce coding complexity significantly while maintaining similar average picture quality


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