[vod] streaming video over the internet: approaches and
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Streaming Video over the Internet Streaming Video over the Internet Approaches and DirectionsApproaches and Directions
Dapeng WuYiwei Thomas HouWenwu ZhuYa-Qin ZhangJon M. Peha
2001 년 9 월 4 일
발표자 : 서승우
Raw Video
CompressedAudio
Application-layerQoS ControlCompressed
Video
TransportProtocol
VideoDecoder
AudioDecoder
Raw Audio
VideoCompression
AudioCompression
Application-layerQoS Control
TransportProtocol
MediaSynchronization
Storage Device
Streaming Server
Client/Receiver
Internet(Continuous media distribution services)
Six Key AreasSix Key Areas
Video Compression Application layer QoS control Continuous media distribution services Streaming servers Media Synchronization mechanisms Protocols for Steaming media
Two approaches of video compressionTwo approaches of video compression
Nonscalable video coding– Generate 1 compressed bit-stream
Scalable video coding– Generate multiple compressed bit-stream– One is base substream– Others are enhancement substream– SNR , FGS
Six Key AreasSix Key Areas
Video CompressionApplication layer QoS control Continuous media distribution services Streaming servers Media Synchronization mechanisms Protocols for Steaming media
Application-Layer QoS ControlApplication-Layer QoS Control
Congestion Control– Rate Control
Source-Based Rate Control
Receiver-Based Rate Control
Hybrid-Rate Control– Rate Shaping
Frame-dropping filter Layer-dropping filter Frequency filter Re quantization filter
Error Control– FEC– Delay-Constrained
Retransmission– Error-Resilient
Encoding– Error-Concealment
To avoid congestion and maximize video quality in the presence of packet loss
Rate ControlRate Control
Source-Base Rate Control– Probe-Based
Maintain their packet loss ratio below a certain threshold
– Model-Based Based on throughput model
Rate ControlRate Control
Receiver-Based Rate-Control– When no congestion is detected,join a
layer/channel =>Result in an increase of its receiving rate
– When congestion detected, drops a layer
=> result in a reduction of its receiving rate Hybrid Rate-Control
– Both Sender and receiver control rate
Rate ShapingRate Shaping
To match the rate of a pre-compressed video bit stream to their target rate constraint
Required for source based rate control
Codec filter Frame-dropping filter Layer-dropping filter Frequency filter Re-quantization filter
Error ControlError ControlFEC: add redundant informationFEC: add redundant information
Channel coding :– Packetized into k packets– Generate n packet block ( k < n)– Only need to receive any k packets in n packet block
Source coding-based FEC– N-th group of blocks contains redundant information
of (n-1)th group of blocks Joint source/channel coding
– Optimal allocation between source coding and channel coding
Error ControlError ControlDelay-Constrained RetransmissionDelay-Constrained Retransmission
Error ControlError ControlError-Resilient EncodingError-Resilient Encoding
MDC : Multiple description coding– Compressed into multiple streams– Each description provides acceptable
visual quality– With only one description, can
reconstruct video with acceptable quality
– COST !!
Error ControlError ControlError ConcealmentError Concealment
Reconstruct the missing data in intra-coded frames in inter-coded frames
Example of skills– Maximally smooth recovery– projection onto convex sets– various motion vector– coding mode recovery methods
Six Key AreasSix Key Areas
Video Compression Application layer QoS controlContinuous media distribution service
s Streaming servers Media Synchronization mechanisms Protocols for Steaming media
Continuous Media Distribution ServicesContinuous Media Distribution Services
Network FilteringApplication-Level MulticastContent Replication
Network FilteringNetwork Filtering
Network FilteringNetwork Filtering
Typically, frame-dropping filters are used as network filters
Application-Level MulticastApplication-Level Multicast
IP multicast has barrier– Scalability,network
management,deployment,support for higher layer functionality
=> application level multicast mechanism was proposed
Media-Bridge– Performs routing at application layer– Interconnect with neighbor Media-Brides through
explicit configuration– Application level multicast is possible
Content ReplicationContent Replication
Mirroring– Place copies of the original multimedia files
on other machines scattered around the Internet
Caching– Makes local copies of contents that clients
retrieve frequently
– To store complete video is expensive– A few cached frames can contribute to
significant improvement in performance
Six Key AreasSix Key Areas
Video Compression Application layer QoS control Continuous media distribution servicesStreaming servers Media Synchronization mechanisms Protocols for Steaming media
Streaming ServersStreaming Servers
Real-Time Operation SystemStorage System
Streaming ServersStreaming ServersOS:process managementOS:process management
EDF : each task is assigned deadline – close to deadline first
Rate-monotonic scheduling– high rate task first– More task switching
< EDF vs Rate monotonic >
Streaming ServersStreaming ServersOS:Resource ManagementOS:Resource Management
Resource management involves admission control and resource allocation
Deterministic admission control– Hard guarantees
Statistical admission control– Statistical guarantees
Streaming ServersStreaming ServersOS:File ManagementOS:File Management
Non-scatterd vs scattedScatted
– throughput improved– Seek times can be reduced by disk-schedul
ing algorithms SCAN-EDF, grouped sweeping scheduling,DC-SCAN
Support pause/resume,fast forward,fast backward => under study
Streaming ServersStreaming ServersStorage SystemStorage System
Increase throughput with data striping– load-balance and low latency are two conflicting objectives
Streaming ServersStreaming ServersStorage SystemStorage System
Increase capacity with tertiary and hierarchical storage– To keep the storage cost down , tertiary
storage must be added
SAN : use fiber channel
NAS : directly attach to a local area network
Six Key AreasSix Key Areas
Video Compression Application layer QoS control Continuous media distribution services Streaming serversMedia Synchronization mechanisms Protocols for Steaming media
Media SynchronizationMedia Synchronization
Intra-stream synchronization– Maintain continuity of logical data
unitInter-stream synchronization
– Maintain temporal relationships among different continuous media
Inter-object synchronization– Relation with time-independent data
such as text, still image and streams
Media SynchronizationMedia Synchronization
Methods maintain the temporal relations– Interval-based– Axes-based : time stamping
Widely used
– Control flow-based– Event-based
Six Key AreasSix Key Areas
Video Compression Application layer QoS control Continuous media distribution services Streaming servers Media Synchronization mechanismsProtocols for Steaming media
Protocols For Streaming VideoProtocols For Streaming Video
Transport ProtocolsSession Control Protocols
Protocols For Steaming VideoProtocols For Steaming VideoTransport ProtocolsTransport Protocols
TCP – retransmission
UDP– Typically employed as the transport
protocol
Protocols For Steaming VideoProtocols For Steaming VideoTransport ProtocolsTransport Protocols
RTP : does not guarantee QoS or reliable delivery
– Time stamping– Sequence numbering– Payload type identificatio
n– Source identification
RTCP : designed to work in conjunction with RTP
– QoS feedback– Participant identification– Control packets scaling– Inter-media synchronizati
on– Minimal session control i
nformation
Protocols For Steaming VideoProtocols For Steaming VideoSession Control ProtocolsSession Control Protocols
RTSP– Support VCR-like control operations– (stop,pause/resume,fast forward, fast backward)– Choosing delivery channel(UDT,multicast UDT, TCP)– Establish and control streams of continuous audio and video
media– Media retrieval : media request,ask session setup to server– Adding media to an existing session
SIP– Support user mobility by proxying and redirecting request
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