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An Active Buffer Management Technique for Providing Interactive Functions in Broadcast Video-on-Demand Systems Zongming Fei, Member, IEEE, Mostafa H. Ammar, Fellow, IEEE, Ibrahim Kamel, Member, IEEE, and Sarit Mukherjee, Member, IEEE IEEE TRANSACTIONS ON MULTIMEDIA, VOL. 7, NO. 5, OCTOBER 2005

Outline zIntroduction zBackground and related work zThe idea of Active Buffer Management zProviding VCR functions in partitioned video broadcast zSimulation results zConclusion

Introduction(1/2) zMulticast VoD service {On-demand batching {Continuous broadcast

zGoal: {Provide interactive functions in broadcast VoD system

Introduction(2/2) zProblem: {Provide VCR functions {Discontinuity of playback

zSolution: {Selectively prefetch segments from broadcast channels {Feasible points to adjust client’s destination

Outline zIntroduction zBackground and related work zThe idea of Active Buffer Management zProviding VCR functions in partitioned video broadcast zSimulation results zConclusion

Partitioned video broadcast z Partitioned video broadcast {Divide video into segments {Uses one channel to send each segment in cycles {More channel, less startup latency

z Let bandwidth=B Mbit/s z Bandwidth of each channel=b Mbit/s z Channel number K=

Weight function z Divide video of length L into K segments z Let channel i periodically broadcast segment i (1 ≤ i ≤ K) z Each segment size is determined by weight function z Size of segment i is

Weight function z Goal : minimize startup latency {Make increase as fast as possible {Can’t be too fast : continuity problem !

z Skyscraper broadcasting scheme: {Series generated by {Upper bound W : ser

: 1,2,2,5,5,12,12,25,25… to W if >W

z Analyze the problems encountered while try to provide interactive functions in these schemes z Design new broadcasting series more suitable

VCR Actions z z z z z

Jump Forward/Backward (JF/JB): Fast Forward/Backward (FF/FB): Slow Forward/Backward (SF/SB): Pause: Play/Play Backward:

Outline zIntroduction zBackground and related work zThe idea of Active Buffer Management zProviding VCR functions in partitioned video broadcast zSimulation results zConclusion

Effect of VCR actions

Conventional Client Buffer Scheme zProblems {Lack of flexibility for providing interactive functions {Consecutive VCR actions in the same direction may made the play point ultimately move to boundary

Active buffer manager zKeep the play point in the middle of the buffer {Lower probability that VCR actions will move the play point outside the buffer

zBuffer manager {Adjust the content of the buffer after VCR action {Selectively download segments from broadcast channel

Active buffer manager zthe client buffer hold 3 segments zCase 1: No VCR actions download K+2 Play point

K+1 K

discard

Download finish

K+3

Active buffer manager zCase 2: Fast forward

Download finish

download

K+4 K+3

K+2 Play point

K+1 K

discard

Destination Adjustment for VCR Actions zClient can resume normal play after VCR actions zThere is always destination point ouside client buffer {Adjust the destination point to feasible point

Outline zIntroduction zBackground and related work zThe idea of Active Buffer Management zProviding VCR functions in partitioned video broadcast zSimulation results zConclusion

A VCR-Oriented Broadcasting Series z Segment size =1,2,4,4,8,16,16,32,64,64, z Let the series increase as fast as possble z Set parameter to limit the maximum number of the series

VCR function implementation with active buffer management scheme zClient required 3 buffers with the same size as the maximum segment z3 loaders download from 3 channels zTwo components to work with VCR functions {Player : accept user interaction commands {loader/buffer manager: decide which channel the client can download segments

player zAccept VCR command {Check whether the content is in the buffer {Check whether the destination point is feasible

zAssume current play point in segment k {Pyramid phase zK, k+1,k+2 should allocate loader

{Equal segment phase zK-1, k,k+1 should allocate loader

loader/buffer manager z Allocate loader/buffers to channel z Pyramid phase {Allocate loader to segments K+1,k+2,k+3

z Equal segment phase {Play point in the early half z Allocate loader to segments K-1,k,k+1

{Play point in the later half z Allocate loader to segments K,k+1,k+2

z More loader/buffer is feasible z Key problem: select a appropriate channel to download required segments

Feasible point z Deal with discontinuity problem z Definition: { { { {

: start postion of segment i : end postion of segment i : broadcasting point of channel i : represent video between two y1, y2

z The segment contains destination point d is called Target segment z Consider some rule for feasible point

Feasible point: case 1 If

is in the buffer, then is feasible.

Feasible point: case 2 case 2.1: If

and

are in the buffer, then d is feasible.

case 2.2: If

are in the buffer, then is feasible.

Feasible point: case 3

z Consider the case destination pointd is after the channel point Cj {designate next segment as target segment

Outline zIntroduction zBackground and related work zThe idea of Active Buffer Management zProviding VCR functions in partitioned video broadcast zSimulation results zConclusion

Experiment settings zVideo length :120 min zDivide the video into 30 segments for 30 channels to broadcasting zFirst 8 segments are unequal size,the others are in equal size zFirst segment is 4.83sec,the largest segment is 5.15min zBuffer size is 3 times the largest segment

User interaction model

Experiment Definition(1/2) z Pi :probablity of issuing specific VCR actions z Reduce parameters:Set p7=p8=p9=0 z Let ,and we have z Let for 1≤ i ≤6 z Define as duration ratio z Experiment in two ways {Change probability : we let =0.5 and vary from 0.1 to 0.9. {Change duration ratio . : we change the duration ratio from 0.2 to 1.0.

Experiment Definition(2/2) zPercentage of VCR actions: {The higher this percentage , the better interactive performance of the system

zPercentage of destination shift: {The smaller this percentage, the better performance of the system.

Numerical Results

Numerical Results

Numerical Results

Numerical Results

Outline zIntroduction zBackground and related work zThe idea of Active Buffer Management zProviding VCR functions in partitioned video broadcast zSimulation results zConclusion

Conclusion zA VCR-Friendly broadcast series zActive buffer management technique {Provide functionality of interactive services in broadcast VoD systems.

zThe scheme can implement VCR actions through buffering with high interaction levels.