multimedia information system lab. network architecture res. group cooperative video streaming...

MultimediaInformationSystem Lab.

NetworkArchitectureRes. Group

Cooperative Video Streaming Mechanismswith Video Quality Adjustment

Naoki Wakamiya

Osaka University, Japan

2001/11/07 N. Wakamiya 2

MultimediaInformationSystem Lab.

NetworkArchitectureRes. Group

Video streaming system with proxies

• To provide low-delay and high-quality streaming service

Video Server

Proxy Cache

HeterogeneousClients

2001/11/07 N. Wakamiya 3

MultimediaInformationSystem Lab.

NetworkArchitectureRes. Group

Issues

• Segmentation of video streams• Video quality adjustment• Locating the appropriate server• Cache management• Prefetching

2001/11/07 N. Wakamiya 4

MultimediaInformationSystem Lab.

NetworkArchitectureRes. Group

Protocols

• Each system entity communicates with each other

Video Server

Proxy Cache

Client

2001/11/07 N. Wakamiya 5

MultimediaInformationSystem Lab.

NetworkArchitectureRes. Group

Video block transfer

Video ServerNeighboring Proxy

Proxy Cache Server

Client

PLAY messagewith QoS

Cache Hit1. Read block from cache

2. Quality adjustment

Play outInitial buffering 1/fps

Prefetching1. Check cache

2. Request block transfer3. Cache

Cache Miss1. Determine helper server2. Request block transfer

3. Quality adjustment & cache

Freeze tim

e

2001/11/07 N. Wakamiya 6

MultimediaInformationSystem Lab.

NetworkArchitectureRes. Group

Cache table

• Cache table is used to maintain information of locally cached blocks– block number – quality of cached block– marker

• Marker is used to imply the possibility that the block will be required by the other proxies

• Range of marking is limited by inquiry window• QUERY and REPLY messages are exchanged to

update markers

i)(iq

)(iM

I

2001/11/07 N. Wakamiya 7

MultimediaInformationSystem Lab.

NetworkArchitectureRes. Group

Remote table

• Remote table is used to maintain information of blocks cached at the other servers (video server, proxies)– estimated one way delay– estimated throughput– quality of offerable block

• Delay and throughput are estimated using measurement tools or TCP-friendly control mechanisms

• QUERY and REPLY messages are exchanged to update remote tables

Skd

Skr

)(iOk

2001/11/07 N. Wakamiya 8

MultimediaInformationSystem Lab.

NetworkArchitectureRes. Group

Block retrieval algorithm

• the proxy determines the quality of block to offer to client based on– request – cache and remote tables– estimations , – the number of blocks in the client’s prefetch

buffer– parameter

• If the quality of block offerable using cache satisfies , it is regarded as “cache hit”

)(iq j

Cjd

Cjr

ji

jp

j

)()( iqiq jjPj

)(iqPj

2001/11/07 N. Wakamiya 9

MultimediaInformationSystem Lab.

NetworkArchitectureRes. Group

Block prefetching algorithm

• The proxy retrieves the block preparing for the future cache miss

high quality

med quality

low quality

uncached

case 1

case 2

block number

request

request

PrefetchingWindowP

prefetch

prefetch

2001/11/07 N. Wakamiya 10

MultimediaInformationSystem Lab.

NetworkArchitectureRes. Group

Cache replacement algorithm

• Some blocks might be replaced with a newly retrieved block

start end

Inquirywindow

client 1

Inquirywindow

Inquirywindow

client 2

marker

Qualityadjustment

Removal

victim

2001/11/07 N. Wakamiya 11

MultimediaInformationSystem Lab.

NetworkArchitectureRes. Group

Evaluation

• Measurements

– average freeze time

– required buffer size

– degree of satisfactionratio of provided quality to requested quality

• 1 sec block

• P=10, I=20

• initial wait 4 sec

• parameter

• 35 Gbit buffer

Video Server

Proxy Cache

10 Clients

10 Clients

10 Clients

8 Mbps10 msec

5 Mbps20 msec

2 Mbps100 msec

6.0j

2001/11/07 N. Wakamiya 12

MultimediaInformationSystem Lab.

NetworkArchitectureRes. Group

Comparison

• Four mechanisms are compared

0.001

0.01

0.1

1

10

100

1 2 3 4 5 6 7 8 9 10

Ave

rage

Fre

eze

Tim

e [s

ec]

Client

Independent w/o PrefetchIndependent c/w PrefetchCooperative w/o PrefetchCooperative c/w Prefetch

0.6

0.65

0.7

0.75

0.8

0.85

0.9

0.95

1

1 2 3 4 5 6 7 8 9 10

Qua

lity

rat

io

Client

Independent w/o PrefetchIndependent c/w PrefetchCooperative w/o PrefetchCooperative c/w Prefetch

2001/11/07 N. Wakamiya 13

MultimediaInformationSystem Lab.

NetworkArchitectureRes. Group

Conclusion

• The low-delay and high-quality video streaming service is accomplished

• Further efficient control is required• We have to consider implementation issues