video on demand over the internet trends and challenges juergen ehrensberger (heig-vd) andrés...
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Video on Demand over the InternetTrends and challenges
Juergen Ehrensberger (HEIG-VD)Andrés Revuelta (EIG)
Jean-Roland Schuler (EIA-FR)
November 2006
Project Vadese
« Video on Demand and Security » http://www.vadese.org
• Two-years research project• 4 research groups from 3 different schools
(Fribourg, Geneva, Yverdon)• Focuses on the needs of VoD services providers
– Quality of Service – Patching over Peer-to-peer– Digital Rights Management
Video over the Internet
31 October 2006:Swisscom launches Bluewin TV
Video over the Internet
July 2006:Deutsche Telekom launches IPTV
Video over Internet – Market studies
IPTV« Television broadcast over the Internet access »– Worldwide market size (Gartner 2006)
• $870 million in 2006• $13 billion in 2010
Video on Demand« Download or streaming of movies at any time »– Worldwide market size (iSuppli 2006)
• 40% growth in 2005• $2 billion in 2006• $13 billion in 2010
Another market study...
Media distribution over the Internet
Media can be transferred by download or streaming
Download– A file is downloaded from a server to the customer’s equipment– The media can be consumed only after the download has finished
Simple Not suited for live content Long waiting time
Streaming– A continuous media flow of packets is transferred from a server to the customer– The customer consumes the media simultaneously with the transfer
Suited for live content Technically challenging
Network scenario
ISP 1 ISP 2
ISP 3
Home network
Service provider
Low-speed access link(ADSL, CaTV)
High-speed access
TVSet-Top Box
Home network
TVSet-Top Box
Video server
Internet
Quality of Service
• The main challenge of streaming media over this Internet is to obtain a sufficient Quality of Service :
« QoS is the collective effect of service performance which determines
the degree of satisfaction of a user of a service »
(ITU-T Rec. E-800)
Measurable performance parameters
Throughput– ‘Speed’ of the transmission, bits per second received
Packet loss rate– Percentage of packets lost inside the network
Network delay– Delay between the sending of a packet at the source and the
reception by the receiver Delay variation
– Changes of network delay between successive packets
Throughput• Media streams have an inherent bitrate that has to be provided by the
network
Throughput requirements
Transmission capacity
Codec Quality BitrateMPEG-2 TV quality 1 – 4 Mb/sMPEG-4 AVC TV quality 768 kb/sMPEG-4 AVC HDTV 5 – 6 Mb/s
Network Capacity MPEG-4 TV flowsADSL 3 Mb/s 4 flowsEthernet 100 Mb/s 130 flowsISPs / Internet 10 Gb/s 13’000 flows
Packet loss
• What happens if there is too much traffic in the network?– The Internet is a network of transmission links,
connected to routers
Home network
Internet Company network
Company network
Packet loss
• What happens if there is too much traffic in the network?– Each router receives traffic from several input links and
forwards the packet to output links
Packet loss
• What happens if there is too much traffic in the network?– If the output link is occupied, packets have to wait for
transmission in a queue
Packet loss• Transmission queues on routers are causing
packet loss and delays
Measurement over low-capacity access links
Up to 5% packet loss20ms one-way delay
InternetISP
Home network
ADSL (3Mb/s)
HEIG-VD
Access 100 Mb/s
Packet loss, delays
Router
Effect of packet loss on video quality
Example: – 1% loss – MPEG-2– No error concealment
Example: – 5% loss – MPEG-2– No error concealment
Effect of network delay
• Network delay is not critical for non-interactive applications– Typically network delay is below 1 seconds– User may tolerate several seconds of delay
Possible problems– « Roberto Baggio Effect »– Channel switching delay
Delay variation
• Media playback requires a constant flow of data• The packets of the media flow experience different network delays
• A playout buffer compensates the delay variations• Half-filled upon start of the transmission (« Buffering... ») Increases network delay
– Delay variations should be small to keep playout buffer small
Internet
SenderReceiver
Isochronous flow
Isochronous flow
Variable network delays
Playout buffer
Playback application Source application
Current challenges
Insufficient QoS over ADSL and CaTV– Overdimensioning or VDSL– QoS mechanisms in the ISP network– QoS mechanisms on user’s Set-Top Box
High cost for streaming individual flows– « Patching » of video flows– Peer-to-peer distribution of flows
Digital Rights Management
Overdimensioning of the access link
• ADSL link with 3 Mb/s• MPEG-4 AVC video with TV quality at 768 kb/s Additional traffic (Web, E-mail, downloads) may deteriorate the video quality
InternetISP
Home network
ADSL (3Mb/s) Access 100 Mb/s
Service provider
TV Set-Top Box Video server
Dynamic overdimensioning• ISP dynamically increases ADSL capacity
during video streaming– Should provide sufficient capacity for
video and additional downloadsProblem: traffic demand adapts to available
capacity
Very High Bitrate DSL (VDSL2)• Provides capacity of 20 Mb/s (over 1500m)• Allows simultaneous transmission of 2
HDTV channels• Problem: high investment required to
upgrade the access network
QoS mechanisms in the ISP network
ISP Home network
Set-Top Box
• Even over ADSL, a sufficient QoS can be provided using QoS mechanisms• Idea: give video flow priority over other traffic
– Video flow gets sufficient capacity to avoid packet loss on the ADSL link– Other traffic (Web, download) is still possible, but slower
QoS mechanisms in the ISP network
• Even over ADSL, a sufficient QoS can be provided using QoS mechanisms• Idea: give video flow priority over other traffic
– Video flow gets sufficient capacity to avoid packet loss on the ADSL link– Other traffic (Web, download) is still possible, but slower
ISP Home network
Set-Top Box
High priority queue
Low priority queue
Video flow
Other traffic
QoS mechanisms on user’s Set-Top Box• Solution developed in Vadese• Modifications of the access network are costly• Service providers do not own the access network• How can a service provider offer sufficient QoS?
– Use QoS mechanisms on the Set-Top Box Has to control traffic after it has crossed the ADSL link!
ISP Home network
Set-Top Box
Video flow
Other traffic
QoS mechanisms on user’s Set-Top Box
• Non-video traffic mainly uses TCP– TCP adapts to network congestion, detected by packet loss
• Control queue length on ISP router from Set-Top Box– « Split » Advanced Queue Management
ISP Home network
Video flow
Other traffic
Low queue occupancy
Discard non-video packets
Controled TCP traffic
Measure video QoS
High cost for Video-on-Demand• In VoD, customers access videos at different moments• The simple approach to start a new flow for each user is not
economical– Example : access link at 1 Gb/s
Only 200 simultaneous HDTV flows (at 5 Mb/s)Cost of $1 per video, only for transmission
Internet
High-speed access 1 Gb/s
Service provider
Video server
Near Video-on-Demand with Multicast• Solution
– A new flow for the same video starts every n minutes– Similar to a TV broadcast that repeats every n minutes– Flow is efficiently transmitted via multicast
• Multicast is only feasible for network operators
Service provider
Video server
Home network
Home network
Set-TopBox
Set-TopBox
Multicast flow
Video patching with Peer-to-peer• Solution developed in Vadese• Allows true Video-on-Demand • Can be used by service providers without their own multicast network• Idea of patching:
– A customer who already receives a video can relay the flow to a new customer– The missing part of the video is temporarily ‘patched’ from the server
Service provider
Video server
Home network
Home network
Set-TopBox
Set-TopBox
Patching flow
Peer-to-peer flow
True Video-on-Demand with Multicast• Possible alternative to Peer-to-peer transmission• Combines Multicast and Patching to achieve true Video-on-Demand• Solution
– A new multicast flow for the same video starts every n minutes– When a new customer arrives, it joins an existing multicast session– The missing first minutes of the movie is patched by a short-lived patching flow
Service provider
Video server
Home network
Home network
Set-TopBox
Set-TopBox
Multicast flow
Patching flow
Joins multicast
Conclusion
Project Vadese - Video on Demand and Security– Focuses on the needs of VoD services providers
• Quality of Service • Patching over P2P• Digital Rights Management
– Technologies will be integrated in a Set-Top Box– Possible valorizations
• Follow-up projects with commercial partners• Intellectual property• Commercialization of some of the technologies