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
Introduction
Background and related work
The idea of Active Buffer Management
Providing VCR functions in partitioned
video broadcast
Simulation results
Conclusion
Introduction(1/2)
Multicast VoD service
On-demand batching
Continuous broadcast
Goal:
Provide interactive functions in broadcast VoD
system
Introduction(2/2)
Problem:
Provide VCR functions
Discontinuity of playback
Solution:
Selectively prefetch segments from broadcast
channels
Feasible points to adjust client’s destination
Outline
Introduction
Background and related work
The idea of Active Buffer Management
Providing VCR functions in partitioned
video broadcast
Simulation results
Conclusion
Partitioned video broadcast
 Partitioned video broadcast
Divide video into segments
Uses one channel to send each segment in cycles
More channel, less startup latency
 Let bandwidth=B Mbit/s
 Bandwidth of each channel=b Mbit/s
 Channel number K=
Weight function
 Divide video of length L into K segments
 Let channel i periodically broadcast
segment i (1 ≤ i ≤ K)
 Each segment size is determined by weight
function
 Size of segment i is
Weight function
 Goal : minimize startup latency
Make
increase as fast as possible
Can’t be too fast : continuity problem !
 Skyscraper broadcasting scheme:
Series generated by
Upper bound W : ser
: 1,2,2,5,5,12,12,25,25…
to W if
>W
 Analyze the problems encountered while
try to provide interactive functions in these
schemes
 Design new broadcasting series more
suitable
VCR Actions





Jump Forward/Backward (JF/JB):
Fast Forward/Backward (FF/FB):
Slow Forward/Backward (SF/SB):
Pause:
Play/Play Backward:
Outline
Introduction
Background and related work
The idea of Active Buffer Management
Providing VCR functions in partitioned
video broadcast
Simulation results
Conclusion
Effect of VCR actions
Conventional Client Buffer Scheme
Problems
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
Keep the play point in the middle of the
buffer
Lower probability that VCR actions will move
the play point outside the buffer
Buffer manager
Adjust the content of the buffer after VCR action
Selectively download segments from broadcast
channel
Active buffer manager
the client buffer hold 3 segments
Case 1: No VCR actions
download
K+2
Play point
K+1
K
discard
Downloa
d finish
K+3
Active buffer manager
Case 2: Fast forward
Downloa
d finish
download
K+4
K+3
K+2
Play point
K+1
K
discard
Destination Adjustment for VCR Actions
Client can resume normal play after VCR
actions
There is always destination point ouside
client buffer
Adjust the destination point to feasible point
Outline
Introduction
Background and related work
The idea of Active Buffer Management
Providing VCR functions in partitioned
video broadcast
Simulation results
Conclusion
A VCR-Oriented Broadcasting Series
 Segment size =1,2,4,4,8,16,16,32,64,64,
 Let the series increase as fast as possble
 Set parameter to limit the maximum number of
the series
VCR function implementation with active
buffer management scheme
Client required 3 buffers with the same size
as the maximum segment
3 loaders download from 3 channels
Two components to work with VCR functions
Player : accept user interaction commands
loader/buffer manager: decide which channel
the client can download segments
player
Accept VCR command
Check whether the content is in the buffer
Check whether the destination point is feasible
Assume current play point in segment k
Pyramid phase
K, k+1,k+2 should allocate loader
Equal segment phase
K-1, k,k+1 should allocate loader
loader/buffer manager
 Allocate loader/buffers to channel
 Pyramid phase
Allocate loader to segments K+1,k+2,k+3
 Equal segment phase
Play point in the early half
 Allocate loader to segments K-1,k,k+1
Play point in the later half
 Allocate loader to segments K,k+1,k+2
 More loader/buffer is feasible
 Key problem: select a appropriate channel to
download required segments
Feasible point
 Deal with discontinuity problem
 Definition:




: start postion of segment i
: end postion of segment i
: broadcasting point of channel i
: represent video between two y1, y2
 The segment contains destination point d
is called Target segment
 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
 Consider the case destination pointd is after
the channel point Cj
designate next segment as target segment
Outline
Introduction
Background and related work
The idea of Active Buffer Management
Providing VCR functions in partitioned
video broadcast
Simulation results
Conclusion
Experiment settings
Video length :120 min
Divide the video into 30 segments for 30
channels to broadcasting
First 8 segments are unequal size,the
others are in equal size
First segment is 4.83sec,the largest
segment is 5.15min
Buffer size is 3 times the largest segment
User interaction model
Experiment Definition(1/2)
 Pi :probablity of issuing specific VCR actions
 Reduce parameters:Set p7=p8=p9=0
 Let
,and we have
 Let
for 1≤ i ≤6
 Define
as duration ratio
 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)
Percentage of VCR actions:
The higher this percentage , the better
interactive performance of the system
Percentage of destination shift:
The smaller this percentage, the better
performance of the system.
Numerical Results
Numerical Results
Numerical Results
Numerical Results
Outline
Introduction
Background and related work
The idea of Active Buffer Management
Providing VCR functions in partitioned
video broadcast
Simulation results
Conclusion
Conclusion
A VCR-Friendly broadcast series
Active buffer management technique
Provide functionality of interactive services in
broadcast VoD systems.
The scheme can implement VCR actions
through buffering with high interaction
levels.