Video Modeling

Pravin Rajamoney

CSE-581 Network Technology

Papers:

• Analysis, Modeling and Generation of Self-Similar VBR Video Traffic. M.W.Garrentt and W.Willinger

• The Correlation Structure for a Class of Scene-Based Video Models and Its Impact on the Dimensioning of Video Buffers. M.M.Krunz and A.M.Ramasamy

• Hurst Parameter Estimation of Long-Range Dependent VBR MPEG Video Traffic in ATM Networks. S.H.Hong, R.Park and C.B.Lee

• Simple and Efficient Models for Variable Bit Rate MPEG Video Traffic. O.Rose

Acronyms

MPEG Moving Pictures Expert Group

VBR Variable Bit Rate

CBR Constant Bit Rate

GOP Group of Pictures

ATM Asynchronous Transfer Mode

SRD Short Range Dependent

LRD Long Range Dependent

MPEG-2 Video Theory

GOP = 12 IBBPBBPBBPBB

I Picture = Intra coded pictures

P Picture = Predictive coded pictures

B Picture = Bi-directionally coded pictures

2 min review on

Field rate2 fields per frame

Frame rate29.97 frames per second (US) NTSC25 frames per second (Europe) PALLess for computers

Spatial encoding

Temporal encoding

MPEG-2 Video Theory

CBR vs. VBR

CBR videoAdvantage:

• Fluid flow video model

• easier buffer management

• easier on the network

Disadvantage:

• Not bandwidth efficiente.g. If average video bandwidth is 1.5Mbps, but its spike are as high

as 3.5Mbps. Network must always guarantee 3.5Mbps

CBR vs. VBR

VBR videoAdvantage:

• Bandwidth efficient

• Bursty

Disadvantage:

• Difficult to model

• Buffer management required

• Data rate control required

Why model VBR video?

• Simulation• Analyze the stream for a particular network.

How do you make sense out of this?

Types of video modeling

• Probability density of Gamma/Pareto model ( modified bell shape)

• Scene-oriented model

• Markov chain model

• Histogram model (0th order Markov chain)

Gamma/Pareto model

Short Range Dependence (SRD)• Short time scale 10ms

• 200 frames

• Markov chain model, ARIMA process

Long Range Dependent (LRD)

• Synonymous for “Hurst effect”

• Also know as “persistence phenomena”

Observation of an empirical record being significantly correlated to observation that are far removed in time

Hurst value: 0.5 - ~0.75 Low activity~0.75 - ~0.9 Medium activity ~0.9 - 1 High activity

Hurst parameter is related to the amount of motion involved in the sequence

Why simulate VBR video?

• Calculate minimum reservation rate. R*• Amount of buffering needed in the system

for it not to overflow

Why simulate VBR video?

BANDWIDTHBitrate Bandwidth utilization

Conclusion• LRD must be taken into consideration when

modeling VBR video• VBR video is content dependent• Bandwidth and buffer size depends on the

video mean bit rate• ATM systems:

Peak rate

Sustain rate

Average VBR rate

• Network characterization, for real-time VBR video.