Scalable video distribution techniques

1
Scalable video distribution techniques
PLANETE project presentation

• Laurentiu Barza

Sophia Antipolis 12 October 2000
2
Motivation

• User behaviour
• skewed access Zipf Rule 20/80
• desire rapid access
• may be willing to sacrifice access time and some
  interactivity for lower cost service
• Goal scalable service that provides almost
   true VoD  at a much lower cost

3
Outline

• Basic schemes
• Server-Push Broadcast
• - Baseline
• - DeBey
• - Pyramid Skyscraper
• - Tailor-Made
• Client-Pull with Multicast
• - Batching

4
Baseline Broadcast Scheme

• Continuos multicast of hot videos
• M videos
• K channels
• assign K/M channels to each video
• schedule video start times
•  pay-per-view  model

5
Baseline Broadcast
Length of Movie
3 channels/movie
6
DeBey Broadcast

• Split a video into N equal sized segments
• Segment m is transmitted ONCE every m time
• reduce the mean transmission rate
• peak transmission rate very high

7
De Bey Broadcast
Channels
1
1
1
1
1
1
1
1
1
...
2
2
2
2
2
...
3
3
3
...
Time
t0
t1
t2
t3
t4
8
Pyramid broadcasting

• Split video into N segments of lengths L1,L2,,Ln
• L L1L2Ln
• Segment size Li ? Li1
• lower max access time than baseline scheme
• the client has to listen 2 channels simultaneous
• significant receiver buffering up to 70 of
  video length

9
Pyramid Segmentation
Skyscraper segmentation
10
Skyscraper Broadcasting

• use relative segment size progression 1, 2, 2,
  5, 5, 12, 12, 25, 25, 52, 52
• requires less buffering than pyramid scheme
• requires strict synchronization among the
  multicast channels

11
Tailor-Made approach

• Cover all possible design dimensions
• server transmission rate
• start-up latency
• peak client recording rate
• peak client storage requirements
• Is a modification of de Bey
• all the segments have the same length but are
  transmitted continuously

12
Taylor-Made Approach
Channels
1
1
1
1
1
1
1
1
1
...
2
...
2
2
2
2
...
3
3
3
...
4
4
Time
t0
t1
t2
t3
t4
13
Taylor-Made Approach
Channels
Client joins
1
1
1
1
1
1
1
1
1
...
2
...
2
2
2
2
...
3
3
3
...
4
4
Time
t0
t1
t2
t3
t4
14
Partial conclusion

• Proposed schemes characteristics
• are server-push approach
• are designed for hot video
• vary the way they segment a video
• trade-off server transmission rate, client IO
  bandwidth and client storage and recording
  requirements
• have all non-zero start-up latency

15
Client-pull Batching

• delay request for a video until a certain number
  of requests for that video arrive before the
  video is delivered
• batching is only effective for popular videos
• reduce server and network resource requirements
• start-up latency can be very high
• popularity of required video
• no. Of requests required to schedule a video

16
Controlled multicast

• Controlled Multicast Batching Optimal
  Patching
• define a patch threshold that trades off the size
  of the patches and the frequency in which new
  multicast channels are initiated

17
Catching

• Server broadcast video via dedicated multicast
  channels
• Client
• immediately joins the appropriate multicast
  channel
• requests to the server the missing first part of
  the video
• Server sends the first part to the client via a
  dedicated unicast channel

18
Multicast with caching (Mcache)

• Server multicasts body of a video using
• object channels multicast the body of the video
• patch channels multicast parts of the video
  right after the prefix
• Client initiates two parallel requests
• the prefix from the cache
• video body from the server
• Server calculates schedule and inform client
  which channel and when to join

19
Conclusion

• Various schemes for scalable video distribution
• Concern only hot and popular video
• Emulate the native Video on Demand service while
  requiring much less ressources at the server
• Server Push vs. Client Pull models
• Zero latency vs. Non-zero latency schemes

20
(No Transcript)
21
patched
Prefix(cached)
Body(server)