Scalable and Adaptive RealTime Video Multicast

1
Scalable and AdaptiveReal-Time Video Multicast

• Tatsuya Suda
• University of California, Irvine
• suda_at_ics.uci.edu

2
Real-Time Digital Video

• Multicast Applications
• Mbone, distance learning, live TV broadcast
  (over the Internet)
• Video Characteristics
• delay sensitive, loss tolerant, video source
  behavior difficult to predict
• Need new approach

3
Varying Bandwidth Constraints
S
Varying Bandwidth Constraints Some destinations
can accept more video than others How can a
single video source simultaneously satisfy
everyone?
10 Mbps
8 Mbps
6 Mbps
D1
8 Mbps
1 Mbps
D3
D2
4
SolutionPart 1 Multi-Layered Video
Multi-Layer Encoder
Base layer
Raw Video
Enhancement layer
Base Enhancement Layers
Base Layer
5
Time-Variation in Bandwidth Constraints
Time 1
Time 2
S
S
D1
D1
D3
D2
D3
D2
6
SolutionPart 2 Monitor network status with
feedback

• Feedback packets are generated

S

• Switches indicate congestion in feedback packets

• Feedback is returned to source, which adapts the
  video encoding rates of its layers

D
7
Feedback Implosion
S
D1
D3
D2
8
Addressing Feedback ImplosionThrough Feedback
Polling
S

• Forward feedback packets poll a single
  destination for congestion along the path

• Only polled destinations respond with reverse
  feedback

• Round-robin polling between all destinations

D1
D2
9
SolutionPart 2 Feedback merging
S

• Feedback packets are multicasted to all
  destinations

• All destinations respond

• Switches merge returning feedback packets

D1
D2
10
Addressing Varying Bandwidth ConstraintsDynamical
ly adjust the rate of each layer
2 Layer Codec
8
8
2
4
Combined rate controlled by overall congestion
state
4
11
Addressing Varying Bandwidth ConstraintsDynamical
ly adjust the rate of each layer
2 Layer Codec
8
8
2
4
Combined rate controlled by overall congestion
state
4
12
Multicast VideoSimple Model
Dest1
0.6 Mbps
20ms RTT
Dest2
1 Mbps
Source
MPEG-1 with data partitioning MCR 0.5Mbps
2 Mbps
Dest3
13
Multicast Video Simple Model (explicit rate
feedback)
D1
4 Mbps
r6Mbps
10 Mbps
S
D2
10 Mbps
2.5 Mbps
r7.5Mbps
1.1 Mbps
r8.9Mbps
D3
r Poisson interfering traffic load
MCR 1Mbps