Page ▫ 2. Overview. ▫Introduction. ▫Client-Server Model. ▫Multicast Systems. ▫Peer
to Peer. ▫Streaming over the Air. ▫Future / Conclusion ...
Overview and Trends of Video Streaming over IP Aleksandar Markovic and Frank Neugebauer
Overview Introduction Client-Server Model Multicast Systems Peer to Peer Streaming over the Air Future / Conclusion
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Introduction: Schedule
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Introduction: Streaming / IPTV Definition: Streaming – Transmission of data (audio/video) without the need to complete the transfer prior to playing it.
What is IPTV? – Digital Television – IP link, broadband network – Often: Video on Demand (VoD) Page 4
Media Player Downloading Storing (in the buffer) Playout – Decompression – Jitter removal – Decoding
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Client-Server Model
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CDN (1/2)
Contend Distributed Networks increased chance for delay and loss consumption of a large amount of bandwidth Page 7
CDN (2/2)
web browser sends a request to the web server most optimal replicate computed according to client position Page 8
Multicast: Definition Definition: – One to many routing topology – Intention to save bandwidth – IPv4
Usage: – Live Video transmission – MBone Page 9
Multicast: History History: – Defined 1980s (RFC 966 and 1112) – 1st transmission 1992
Multicast: Details Structure: – UDP – Klasse D IP: 1110 + GrouppenID (224.0.0.0 bis 239.255.255.255) – IGMPv1 • Leaving not specified till v2 • v3 as Draft Page 11
Multicast: Problems Due to UDP: – Unreliable transmission – No congestion control or QoS – Solution: RMTP
Business: – Unicast “good enough” – Multicast routers expensive • ISPs see no reason to spend money Page 12
Multicast: Future (1/2) Outlook: – IPv4: End of lifecycle • Address Space almost consumed – Many unicast architectures (CDN, P2P) are workarounds • Multicast more effective alternative • Internet operates near full capacity: performance increase necessary to avoid “brownout” Page 13
Multicast: Future (2/2) IPv6: – Multicast already implemented – Consumers become more mobile • Tend to consume more flexible – New Usages: • MMORPG • IPTV • VoD Æ Reduce infrastructure costs Page 14
Peer-To-Peer Systems No router support required Utilization of the application layer Users act both as clients and servers Approaches: – tree-based (push) – mesh-based (pull)
Creation and maintenance of good topology crucial – exchange of data in an efficient, cost-aware manner – delay between peers minimized – number of connections between peers minimized Page 15
Single-Tree Streaming (1/4) many possible ways to construct a streaming tree major considerations: – depth of the tree – fan-out of the nodes
number of children depends on uploading bandwidth
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Single-Tree Streaming (2/4) Problem: user might leave the streaming session unexpectedly (peer churn) Descendant peers cut off from receiving data
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Single-Tree Streaming (3/4) Tree topology: – Centralized » fast recalculation of topology » server possible bottleneck – Decentralized » independence from central server » very slow
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Single-Tree Streaming (4/4) Users grouped into session based on arrival time Group forms a multicast-tree, denoted as base tree When a new client joins, then it – must obtain the patch – joins the base tree and retrieves the base stream
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Multi-Tree Streaming Major drawback of single-tree approach: bandwidth of leaf nodes not utilized Construction of multi-tree system, peers at different positions
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Mesh-based systems freedom of structure overlay a tracker keeps info about active peers each peer updates its list about neighbors basic data unit: video chunk pulling and buffering of chunks for certain time
Streaming OTA: Next Gen IPTV IPTV 2.0: – Next Generation Network • Converged network – High bandwidth – QoS – Security – Any User should be able to create or consume content whenever he wants Page 24
Streaming OTA: Next Gen IPTV IPTV 2.0 (cont’d): – Higher image resolution – On mobile devices – No longer walled garden architecture from ISP – Location based / context sensitive services – Seamless mobility
Streaming OTA: Wide Area Cheap setup Metropolitan areas Shared Medium – Good for broadcast – Bad for unicast
Prone to errors – FEC – SVC Page 27
Streaming OTA: Near Field Resilient against interference Scatter Networks – 50 KB/s – Low resolution video – User generated content – Usefull at gatherings
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Streaming OTA: SVC Encoding in layers – Base layer – Enhancement layers
Different streams Tradeoff – higher video quality – lower efficiency of decoding – Encode once, play everywhere Page 29
Future: Ubiquitous mobile streaming with SVC Page 31
The End
Any Questions? German and English welcome
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Discussion P2P vs. Multicast: What has more potential? Where do you see the future of IPTV? What are advantages/drawbacks of IP Multicast compared to P2P? In what situations shall the tree-approach be utilized? When is the mesh-approch more suitable? In tree approach, the coordinating server can become the bottleneck of the system. Is there less probability for the tracker in a mesh-based system to become the bottleneck?
