Multimedia Information System Lab. Network Architecture Res. Group Cooperative Video Streaming Mechanisms with Video Quality Adjustment Naoki Wakamiya Osaka University, Japan
Dec 13, 2015
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