Download presentation
Presentation is loading. Please wait.
Published byMargaretMargaret Harrell Modified over 9 years ago
1
A Comparison of Layering and Stream Replication Video Multicast Schemes Taehyun Kim and Mostafa H. Ammar Networking and Telecommunications Group Georgia Institute of Technology Atlanta, Georgia
2
Research Goal A systematic comparison of video multicasting schemes designed to deal with heterogeneous receivers Replicated streams Cumulative layering Non-cumulative layering
3
Stream Replication Multiple video streams Same content with different data rates Receiver subscribes to only one stream Example DSG (Cheung, Ammar, and Li, 1996) SureStream of RealNetworks Intelligent streaming of Microsoft
4
Replicated Stream Multicast
5
Cumulative Layering 1 base layer + enhancement layers Base layer Independently decoded Enhancement layer Decoded with lower layers Improve the video quality Example RLM (McCanne, Jacobson, Vetterli, 1996) LVMR (Li, Paul, and Ammar, 1998) MPEG-2/4, H.263 scalability modes
6
Layered Video Multicast
7
Layering or Replication? Common wisdom states: “Layering is better than replication” But it depends on Layering bandwidth penalty Specifics of encoding Protocol complexity Topological placement of receivers
8
Bandwidth Penalty Information theoretic results R(P, 2 ) R(P, 1, 2 ) Packetization overhead Syntactically independent layering Picture header GOP information Macroblock information
9
Experimental Comparison
10
Comparison by DP J. Kimura, F. A. Tobagi, J. M. Pulido, P. J. Emstad, "Perceived quality and bandwidth characterization of layered MPEG-2 video encoding", Proc. of the SPIE, Boston, MA, Sept. 1999"
11
Providing a Fair Comparison Need to insure that each scheme is optimized Two dimensions Selection of stream/layer rates Assignments of streams/layers to receivers
12
Rate allocation Cumulative layering Optimal receiver partitioning algorithm (Yang, Kim, and Lam) Stream replication Cumulative rate allocation
13
Stream assignment Cumulative layering Assign as many layers as possible Stream replication Greedy algorithm
14
Comparison Methodology Model of network Topology Available bandwidth Placement of source and receivers Determine optimal stream rates and allocation Evaluate performance
15
Performance Metrics Average reception rate Total bandwidth usage Average effective reception rate Efficiency
16
Network Topology GT-ITM Number of server = 1 Number of receivers = 1,640 Number of transit domains = 10 Number of layers = 8 Amount of penalty = 25%
17
Data reception rate
18
Bandwidth usage
19
Effective reception rate
20
Efficiency
21
Effect of overhead
22
Effect of the number of layers
23
Clustered Distribution Topology consideration Layering favors clustered receivers Stream replication favors randomly distributed receivers Simulate when receivers are clustered within one transit domain
24
Effective reception rate
25
Protocol Complexity Layered video multicasting Multiple join for a receiver Large multicast group size Replicated stream video multicasting One group for a receiver Small multicast group size
26
Average group size
27
Conclusion Identified the factors affecting relative merits of layering versus replication Layering penalty Specifics of the encoding Topological placement Protocol complexity Developed stream assignment and rate allocation algorithm Investigated the conditions under which each scheme is superior
28
Optimal Quality Adaptation for MPEG-4 Fine-Grained Scalable Video Taehyun Kim and Mostafa H. Ammar Networking and Telecommunications Group Georgia Institute of Technology Atlanta, Georgia
29
Related Work (1/2) S. Nelakuditi, et al, “Providing smoother quality layered video stream,” NOSSDAV 2000 Goals Achieving smoother quality for layered CBR video using receiver buffer Minimizing quality variation (maximizing runs of continuous frames)
30
Algorithm Forward scan Switching between select and discard phase Entering select phase if buffer is full Entering discard phase if buffer is empty Backward scan Exploiting the residual buffer Extending each run
31
Bandwidth Model
32
Experimental Result
34
Related Work (2/2) D. Saparilla, et al, “Optimal streaming of layered video,” INFOCOM 2000 Goal Investigating the bandwidth allocation problem to minimize loss probability Modeling the source video and the available bandwidth by stochastic process
35
Main Result Static policy Allocating bandwidth in proportion to long run average data rate Optimal for infinite length, independent layering Threshold-based policy If the base layer buffer is below a threshold, allocate bandwidth to the base layer
36
Research Goal of MPEG4 FGS Quality Adaptation Maximization of the perceptual video quality by minimizing quality variation Accommodation of the mismatch between Rate variability of VBR video Available bandwidth variability
37
MPEG4 FGS Hybrid Scalability Base layer Enhancement layer FGS layer: improving video quality FGST layer: improving temporal resolution
38
Rate Variability
39
Quality Adaptation Framework C[k]: transmission resource constraint X[k]: cumulative data size S[k]: cumulative selected data size d: threshold
40
Optimal Quality Adaptation Threshold should be equal to the receiver buffer size to achieve Minimum quality variability Necessary condition of maximum bandwidth utilization
41
Online Adaptation Estimating the threshold point without assuming the available bandwidth information in advance The available bandwidth is estimated by an MA style linear estimator
42
Experiment Model
43
Bandwidth Variability TCP TFRC
44
Performance over TFRC Threshold-based streaming (Infocom’00) Online adaptation
45
Performance over TCP Threshold-based streaming Online adaptation
46
Conclusion Accommodated the mismatch between the rate variability and the bandwidth variability Developed an optimal quality adaptation scheme for MPEG4 FGS video to reduce quality variation Investigated the perceptual quality of different algorithms and options
Similar presentations
© 2024 SlidePlayer.com. Inc.
All rights reserved.