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Internet Media Delivery Systems: Current Design, Open Issues, Research Problems.

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Title: Internet Media Delivery Systems: Current Design, Open Issues, Research Problems.


1
Internet Media Delivery Systems Current Design,
Open Issues, Research Problems.
  • G. S. Greenbaum, Ph.D
  • RealNetworks Codec Group
  • Stanford University
  • Feb 13, 2001

2
(No Transcript)
3
Outline
  • Introduction to Internet-based Media Distribution
    Systems
  • Components
  • A Real Example of a Media System RealSystem iQ?
  • RealProducer 8.5
  • RealSystem Sever 8 and Proxy 8 with Neuralcast
    Technologies
  • RealPlayer 8
  • Open Problems
  • source/channel coding
  • server storage/complexity tradeoffs
  • network traffic optimization problems

4
Introduction Ambitions of a Media Delivery
System
  • The Overall Goal is to Maximize the End-User
    Subjective Experience to Streaming Multimedia
  • A Successful Internet Media Delivery System Must
    Provide
  • Tools for the easy re-purposing of new and extant
    content distribution over digital networks
  • Robust, Distributed, Scalable, Secure, and
    Flexible Architecture for content distribution
  • Ubiquitous client distribution supporting diverse
    data types

5
Introduction Components
Capture Encoding Serving Internet
distribution Playback
IP network
Real Player
Real Server
Real Producer
SDK
SDK
SDK
Plug-ins
Plug-ins
Plug-ins
Real Proxy
Plug-ins
6
Introduction Components
  • Content Creation Digitization and Encoding
  • Most general purpose content starts life in
    analog form which needs conversion to digital
    form
  • Rich multimedia data types audio, video, image,
    VRML, etc.
  • Lossy and lossless modes of compression
  • Download vs Broadcast (streamed) modes
  • Encoding tools typically have little knowledge of
    the distribution network or computational
    resources of the client playback device
  • Metadata for efficient search and retrieval
  • Rights of content provider must be insured

7
Introduction Components
  • Transmission and Distribution
  • Live and pre-recorded Broadcast and VOD modes of
    operation
  • Redundant, Intelligent, and Reliable architecture
    needed
  • Redundant Zero points of failure at each
    critical node of the distribution chain
  • Intelligent Load balancing (dynamic capacity
    allocation) for efficient distribution
  • Reliable Stream distributions that traverse
    public and private network segments fortified
    against loss and congested
  • Architecture usually contains splitters/repeaters
    and caches for efficient usage of network/gateway
    capacity working in both a push and pull mode

8
Introduction Components
  • Client-side Player residing on different
    appliances and diverse networks
  • DSL, Cable Modem, Intranets/firewalls, POTS,
    ISDN, etc.
  • PCs, cellular devices, PDAs, set-top boxes,
    digital VCRs, etc.

9
RealSystem iQ RealProducer 8.5
  • State of the Art Narrowband and Broadband Audio
    and Video Codecs RealVideo 8 and RealAudio 8
  • Pre-processing
  • Noise removal
  • Resampling
  • Inverse-Telecine
  • Deinterlacing
  • Rate control
  • Two-pass, VBR
  • Channel adaptation
  • SureStream, forward unequal ECC, data interleaving

10
Broadcast
SLTA library
File System
File Format
Producer
Live Text
Live Pix
Remote Broadcast Library
Internet/Intranet
11
RealSystem iQ Server 8
  • Adaptive serving
  • Bandwidth detection
  • Stream switching
  • Thinning
  • multicast
  • Designed for distributed
  • delivery networks in mind
  • proxy plug-ins
  • edge-server plug-ins
  • distributed licensing
  • Features
  • Ad Insertion, Authentication extensions, remote
    administration, firewall proxy, etc. (see
    www.realnetworks.com for more details)

12
RealSystem iQ Server 8
Broadcast Applications
Admin, monitoring Applications
Broadcast Plug-in
File Format Plug-in
File System Plug-in
Generic Plug-ins (logging, monitoring, etc.)
Server Core
Packet Sink Plug-in
Allowance Plug-in
Internet/Intranet
13
Server Clustering
Originate Deliver from Any Where An
architecture free from origins and edges
14
Distributed Architectures
15
RealSystem iQ Server 8 Neuralcast Technologies
  • NeuralCast Communications Protocol
  • The ability for a network of RealSystem Servers
    to become self-aware by exchanging information
    and making decisions. Current abilities include
    capacity sharing and capacity fail over in the
    event of a network or equipment issue.
  • NeuralCast Live Distribution
  • The intelligent and reliable delivery of
    broadcasts through a network or RealSystem
    Servers. Current abilities include
    multi-protocol transmission between servers,
    error correcting methods for streams, terrestrial
    and satellite multicast support.
  • NeuralCast Live Redundancy
  • From encoder to server or from server to server,
    the ability to send redundant streams, providing
    a fail-over feed in the event of a network or
    equipment outage.

16
RealSystem iQ Server 8 Neuralcast Technologies
  • NeuralCast Live Distribution
  • Push and Pull models
  • Re-Transmission requests made at receiver not
    originating transmitter
  • FEC configurable
  • Multiple Transport Support allows the same
    broadcast to be transmitted via conventional
    unicast UPD or TCP across non-multicast enabled
    segments

17
RealSystem iQ Server 8 Neuralcast Technologies
  • NeuralCast Live Redundancy
  • Stateless protocol decouples live broadcast
    packet contents from the transmitting network
  • Live broadcast streams that are sent redundantly
    over different networks may be re-converged at
    the Server receiver

Encoder/ SLTA
18
RealSystem iQ Live Webcast Deployment
Server Splitter Relays
19
RealSystem iQ Real Proxy 8
  • Access Provider Deployment Goals
  • Optimize gateway bandwidth for streaming media
  • Eliminate redundant requests for media from
    subscribers for content that is back hauled from
    the public Internet
  • Improve playback quality experience by migrating
    content closer to the viewing subscriber
  • Deployed Technologies
  • RealSystem Proxy near Telco/Cable cross connects
    or at data center

20
RealSystem iQ Real Proxy 8 Deployment
Traffic Management
Cache Acquisition (Cold)
21
RealSystem iQ Real Proxy 8 Deployment
Cache Playback (Hot)
Live Splitting
22
RealSystem iQ RealPlayer 8
  • Post-Filters
  • Sharpening
  • color correction
  • graphic equalizer
  • Rescaling
  • Bandwidth Simulator
  • Reverb
  • Network Aware
  • Monitors Network connection
  • Auto-update enabled to obtain latest player
    components
  • Auto-configures for best transport method
  • Features
  • RV8, RA8, Visualizations, Radio Tuner, Media
    Search, localizations for different languages,
    etc. see www.real.com for a complete list.

23
RealSystem iQReal Client Architecture
RealPlayer
RealJukebox
ActiveX
Netscape Plug-in
Client Core
File Format Plug-in
File System Plug-in
Rendering Plug-in
Generic Plug-ins
Internet/Intranet
24
Open Problems...
Overall minimum-distortion optimization
Source/Channel coding Internet traffic problems
IP network
Real Player
Real Server
Real Producer
Real Proxy
Traffic optimization in dedicated delivery
network
Server storage vs. complexity tradeoff
25
Source Coding IssuesThe Challange
  • Video no adequate distortion measure
  • Human retina - an ultimate 1201 lossy compressor

Human eye has around 6M cones 120M rods but
only around 1M ganglion fibers in the optical
nerve.
26
Source Coding IssuesThe Challange
  • Some other facts from physiology
  • visual recognition requires power of 30 of the
    cortex
  • hearing -- uses just 3 of the cortex
  • Ultimate video decoder 1/3 of a human
    (adequately educated and trained)

27
Source Coding Issues
  • Constraints
  • Bounded delay (1-10 s and/or MB constraint)
  • Targeting many discrete, fixed bit rate
    connections
  • Random-access is necessary
  • Seek/rewind on pre-recorded media
  • Ability to join live stream
  • Packetization Each packet must contain
    sufficient information to be decoded.
  • Low complexity decoding
  • Real-time encoding
  • Need to assume inherently lossy network transport

28
Source Coding Issues
  • Bounded Delay
  • Not as much an issue for Downloadable Media
  • Leveraged to solve inhomogeneity in content bit
    allocation (VBR), network jitter, random access,
    re-transmission requests, etc.
  • Imposes constraints on look-ahead dependencies
  • Imposes constraints on interleaving techniques
    for error mitigation
  • Cannot replicated the remote-control paradigm
    of broadcast television.

29
Source Coding Issues
  • Bandwidth Scalability
  • Layered Scalability, e.g. FGS, annex O.
  • Introduces additional delay
  • Hit in coding efficiency
  • Embedded techniques, e.g. FGS, wavelets
  • Introduces additional delay
  • Possible hit in coding efficiency
  • Multi-Encoding e.g. SureStream
  • Increased file size and possible delivery costs
  • Optimal coding efficiency for targeted rate
  • ?

30
Source Coding Issues
  • How to facilitate random access decoding?
  • independent encoding
  • pre-encoded transitions
  • pre-encoded correlated fragments combined with
    Slepian-Wolf encoding
  • use of multiple-description codes
  • something else???

?
31
Source Coding Issues
  • Packetization
  • Not an issue for downloadable media
  • Imposes constraints on dependencies for streaming
    content leading to a decrease in coding
    efficiency
  • Due to IP and packet reconstruction overhead,
    packet size should be nearly as large as the
    packet fragmentation limit imposed by routers,
    1500 bytes. increased latency of stream
  • Complexity Scalability
  • How does the algorithm scale on limited resource
    devices for the encoder and decoder?
  • Scalable Post-filters
  • Limited decode B-frames dropped or I-frame only
  • Short-cuts limited ME/MC

32
Channel Coding Issues
  • IP have been designed to relieve engineers from
    thinking about physical connection and channel
    coding problems
  • Ironically enough, with streaming media we now
    have to go back to basics
  • UDP is mainly used packet erasures
  • ARQ and ECC
  • Client side mitigation techniques
  • Ideally, we want the server to do adaptive
    channel coding/ transmission. Cost is reduction
    in server load.
  • How much of this work can be done ahead of the
    time by encoder?
  • Is there a way to store all necessary information
    in a compact form? Is SureStream the ideal?

33
Source/Channel Coding Issues
  • Separation Theorem may not hold
  • packets have finite lengths
  • packets can be sent via multiuser channels
  • Should we use joint source/channel coding?
  • How to combine distortion due to lossy
    compression and one due to channel errors
  • can we design a universal lossy joint
    source/channel code?

34
Source/Channel coding problems
  • Another way to deal with IP packets is to use
    multiple-description coding
  • Ozarow (1980) The achievable set of quantuples
    (R1,R2 ,d1,d2,d3) is given by

35
Summary
  • Several embodiments of Media Delivery Systems
    exist today, but the technology is still in its
    toddler years.
  • Many more issues, problems, and questions than
    answers.
  • Plenty of opportunities for grad students,
    post-docs, and professors! (and job security for
    those outside of academia)
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