Multicast

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					Multicast
What is Multicast?

• A new concept for transmitting data over
  computer networks
• Best suited for one-to-many or many-to-
  many delivery of data
• Designed to reduce network load
• Developed for next-generation applications

                   Multimedia Systems
A Brief History

• The interest in building a multicast capable
  Internet achieved critical mass in late 1980s
• MBone has been created in the beginning of
  1990s and grew rapidly after 1992
• Multicast aware routers and lately even
  switches appeared on the market
• Today multicast is still evolving, new
  multicast routing protocols are being
  developed
                    Multimedia Systems
Applications that Need Multicast

• Audio and video conferencing
• Multimedia distribution (audio, video)
• Delivering stock tickers from stock exchanges
  to brokers or businessmen
• “Shared whiteboards” and joint document
  editing by a group
• Distance learning and training (lectures)

                   Multimedia Systems
Specific Multicast Applications?

• There is no “specific” multicast application
• Some think that multicast is suited only for
  bandwidth consuming applications
• Some think that multicast is suited only for
  multimedia delivery applications
• Some think that multicast is suited only for
  applications with large number of receivers

                    Multimedia Systems
  Why Multicast?
                         S                                   • Multicast introduces
                          7
                                                         G
                                                               efficiency in data
                             6               2                 transportation, shifting to
                                                         G
                                 6       3                     the network layer the
Replicated unicast   G                           2
                                 G
                                     G                         responsibility of delivering
                                                     2         packets to all interested end-
                                                 G
                                                         G     stations
                                                             • There are a lot of one-to-
                         S
                                                               many or many-to-many
                                                         G     applications that use
                                                         G     replicated-unicast or
         Multicast   G           G
                                                               broadcast in order to send
                                     G                         data to the receivers, but this
                                                               consumes processing power
                                                         G
                                                 G
                                                               and bandwidth
                                                 Multimedia Systems
How to Understand Multicast…

• Multicast falls between unicast and broadcast
• In fact we can view unicast and broadcast as
  two “degenerate” cases of multicast
• Taking this viewpoint:
      unicast happens when there is a one-to-one data delivery
      broadcast happens when there is a one-to-all data
      delivery


                       Multimedia Systems
The Multicast Groups

• Multicast introduces the concept of a multicast group
• A multicast group has a single multicast group address, all hosts
    from a group will receive the data sent to that address
•   Multicast groups are dynamical, hosts can join and leave a group
    at any time
•   Whether or not to be member of a group is a local decision
•   A group can have any number of members
•   A group can have any shape, size, or geographical extent
•   A host can belong to several multicast groups at the same time
•   The sender(s) do not have to belong to the group(s) to which they
    send traffic
•   Group membership is receiver initiated (!)

                           Multimedia Systems
IPv4 Address Space

• The IPv4 address is 32 bits wide
• The address space has been divided in several
  address classes originally to yield network
  numbers of different sizes
• IP addresses are usually expressed in the
  “dotted-decimal” notation, each address is
  written as four numbers between 0 and 255
  divided by dots (e.g. 130.230.50.30)

                   Multimedia Systems
The IPv4 Address Classes

• There are 4 IPv4            Class A Address    0.0.0.0 - 127.255.255.255
  classes to date: A,         Class B Address   128.0.0.0 - 191.255.255.255
  B, C and D                  Class C Address   192.0.0.0 - 223.255.255.255
• Initially all defined       Class D Address   224.0.0.0 - 239.255.255.255
  addresses were
                               6,25%
  unicast
                            6,25%
• After multicast                                              Class A
  addresses being         12,50%                               Class B
  defined, classes A,                           50,00%         Class C
  B and C are for                                              Class D
  unicast, and class D     25,00%                              Unspecified
  is for multicast
                           Multimedia Systems
The IPv4 Address Syntax

• Class A addresses begin with a 0 bit:
      0 | 7 bits network number | 24 bits host number
• Class A addresses begin with a 10 bit:
      10 | 16 bits network number | 16 bits host number
• Class A addresses begin with a 110 bit:
      110 | 24 bits network number | 8 bits host number
• Class A addresses begin with a 1110 bit:
      1110 | 28 bits multicast group number
                        Multimedia Systems
Reserved Multicast Addresses

• A group can take any address available from the multicast address space.
  However there are some addresses that are reserved and cannot be used,
  since those are reserved for different protocols, certain applications or
  special groups
• Class D addresses starting with 224.0.0.x and 224.0.1.x have been reserved
  for various permanent assignments. For example:
         224.0.0.0 : Base Address
         224.0.0.1 : All Systems on this Subnet
         224.0.0.2 : All Routers on this Subnet
         224.0.0.4 : DVMRP Routers
         224.0.0.5 : OSPF All Routers
         …
         224.0.1.1 : Network Time Protocol
         224.0.1.2 : SGI-Dogfight
         224.0.1.3 : rwhod
         224.0.1.5 : Artificial Horizons – Aviator

                              Multimedia Systems
Other Reserved Multicast Addresses

• The last reserved multicast addresses
  239.0.0.0/8 are set aside for use within private
  networks
• Host groups on the public Internet should not
  use these addresses
• Private networks that employ such addresses
  should not forward packets destined to such
  groups onto the Internet

                    Multimedia Systems
Scoping the Multicast Traffic

• Multicast traffic should be limited, in order not
  to flood the Internet
• Scoping the multicast traffic presents it’s
  difficulties when there are overlapping regions
• There are several ways of scoping the
  multicast traffic (implicit scoping, TTL
  scoping, administrative scoping)

                    Multimedia Systems
Implicit Scoping

• Implicit scoped groups are generally reserved
    multicast addresses
•   These packets are limited to the subnet on which they
    are originally transmitted
•   Both the TTL field is set to 1 (only the current
    subnet), and the routers know not to ever forward
    packets having the destination address within certain
    range
•   The implicit scoped addresses are taken from the
    range 224.0.0.0/24

                        Multimedia Systems
TTL-Based Scoping
• Each IP packet has a field
  containing the TTL (time to
  live)                              TTL          Scope Threshold
• Any router has a TTL value                  0 Restricted to the same host
  assigned to it                              1 Restricted to the same sub-
• Any packet having the TTL                     network
  value less or equal than the            15 Restricted to the same site
  router’s, is not to be                  63 Restricted to the same region
  forwarded                              127 Worldwide
• Any packet having the TTL              191 Worldwide; limited bandwidth
  value greater than the                 255 Unrestricted in scope
  router’s, will be forwarded
  with the TTL value
  decremented by 1
                         Multimedia Systems
Properties of TTL-Based Scoping

• It requires arbitrary choices of TTL ranges in
  order to be effective
• The responsibility of enforcing the scope is
  divided between 2 separate entities: the
  network manager and the users of the source
  station(s)
• Privacy and security policies are not applicable
  if the only administrative metric is the TTL,
  because TTL is indiscriminate
                    Multimedia Systems
Administrative Scoping

• The idea behind administrative scoping is to provide a way to do scoping
  based on the multicast address
• The range 239.0.0.0/8 has been reserved for administrative scoping
• Even if these addresses represent 1/16 of multicast addresses, there still are
  16,777,216 addresses to use

      IPv6 Scope          Description                 IPv4 Prefix
             3                Local                  239.255.0.0/16
             5              Site-local               239.253.0.0/16
             8         Organization-local            239.132.0.0/14


                                Multimedia Systems
Properties of Administrative Scoping

 • An administratively scoped region has fixed
     boundaries
 •   Provides a mechanism for well-defined
     boundaries (which may overlap)
 •   It is a good privacy mechanism (important for
     business conferencing and other private
     information exchange)
 •   All administratively and TTL scoped regions
     must have the following properties:
         They must be convex
         They must be connected or compact

                          Multimedia Systems
Multicast Routing and Forwarding

• Multicast routing protocols are used by multicast
    routers to discover multicast delivery trees
•   Multicast forwarding is the procedure of transmitting
    from one router to another the multicast packets,
    based on the information derived from multicast
    routing protocols
•   Routers get information from the end-stations about
    their group memberships (consequently about the
    active groups) through IGMP
•   Routers maintain the multicast delivery trees through
    specific protocols (DVMRP, PIM, MOSPF)
                        Multimedia Systems
Internet Group Management Protocol

• IGMP is the signaling protocol that the end-stations
    use to signal their group membership interest
•   It is an integral part of IP, every router today is
    supposed to support it
•   There have been two versions of IGMP, and the third
    is being developed as we speak
•   Some companies (i.e. CISCO) have made their own
    version of IGMP for their switches (CGMP)


                       Multimedia Systems
IGMPv1
• One multicast router per LAN must periodically transmit Host
    Membership Query messages, addressed to the all hosts group
•   When an end-station receives an IGMP Query message, or when it
    wants to join a group, it sends a Host Membership Report addressed
    to the group’s address, for each group to which it belongs or in
    which it wants to join
•   In order to avoid a flurry of Reports from every group members,
    each end-station chooses a random delay until it transmits the
    Report(s). If meanwhile it has detected another Report to a group to
    which it is a member, the end-station will not send that Report
    anymore
•   If the router does not receive any Report from any member of a
    group after a number of Queries, it will assume that no group
    members are present on that particular interface, and it will stop
    forwarding the multicast packets for that group on that interface
                             Multimedia Systems
IGMPv2

• All the features from IGMPv1 are present in IGMPv2 with
    some enhancements to improve efficiency
•   The multicast querier is the router with the lowest IP address
•   When an end-station leaves a group, it sends a Leave Group
    message to the all-routers group (224.0.0.2)
•   In IGMPv2 there is a Group-Specific Query addressed only to
    one group, so only one member from that group will send back
    a Report
•   When there are a mixture between IGMPv1 and IGMPv2 end-
    stations and/or routers the IGMPv1 will be used

                           Multimedia Systems
How to Implement a Multicast
Application?

• Decide what the application should do (text chat,
    radio, TV, conferencing, on-demand services, etc)
    considering the necessary and the available
    bandwidth
•   Decide about the size of the intended coverage (LAN
    only, corporate intranet, campus MAN, etc)
•   Decide about the scoping (TTL, administrative)
    considering also on the network configuration

                       Multimedia Systems
Routing Techniques

• Broadcast and Prune
      The multicast data itself is the mean to control the delivery trees
      From time to time the multicast stream is broadcasted, and routers
       which do not have end-stations for those group(s) send backwards a
       prune message in order to remove themselves from the stream
      Protocols and Algorithms: DVMRP, PIM Dense Mode, RPM
• Shared Trees
      There is a central point to which all receivers attach
      Shared trees (rendezvous points) must be joined before the flow of
       data, otherwise the central point doesn’t know of any stream and
       the data stops
      Protocols and Algorithms: MOSPF, PIM Sparse Mode

                           Multimedia Systems
Reverse Path Multicasting Algorithm

• The first datagram is broadcasted                   S
  to all “child” routers
• If a “leaf” router detects that it has                                 G
  no groups interested in that                                          G
  datagram, it sends “upward” a
                                                  G         G
  prune message                                                 G
• Each “non-leaf” router keeps the
  prune messages from it’s children                                     G
  for a period of time. If it has                                   G
  received prune messages from all
  children, it send upwards a prune         • If a leaf-router detects a “first”
  message                                      member of a group, it sends
• After the time delay has passed,             upward a “graft” message. This
  each router purges it’s prune                message is forwarded upwards by
  records and rebroadcast                      the routers until it reaches a active
  “downward” a datagram                        router

                                 Multimedia Systems
Multicast Routing Protocols

• There are several multicast routing protocols: DVMRP, PIM
  (DM, SM), MOSPF
• These protocols rely until today on the Broadcast and Prune
  and Shared Trees routing techniques
• The routing protocols implement the routing algorithms (i.e.
  RPM), each with it’s own special enhancements, depending on
  the network topology or group-members density that they
  focus on
• Each network manager should select inside his/her network the
  routing protocol that is best suited for the network (s)he is
  managing

                         Multimedia Systems
The MBone

• The Internet Multicast Backbone is an interconnected set of
  sub-networks and routers that support the delivery of multicast
  traffic
• The MBone has grown from 40 subnets in four different
  countries, to a few hundred thousands subnets today
• It’s goal was to construct a semi-permanent IP multicast
  testbed to enable the deployment of multicast applications
• The MBone carries audio/video multicasts of IETF, NASA
  Space Shuttle Missions, U.S. House and Senate sessions,
  occasional concerts, sporting events, lectures etc


                          Multimedia Systems
Summary

• We found out what multicast is
• We know why multicast should be used
• We learned how multicast traffic is scoped
• We understood the algorithms with which
  routers route and forward the multicast traffic
• We have seen the true potential of multicast
  trough the MBone
                    Multimedia Systems
Multicasting Digital Video Streams

• The TUT’s Multimedia Laboratory has a project to
    distribute digital streams
•   In the Tietotalo building is installed a system that
    captures satellite and terrestrial digital video streams
•   These streams are multicasted through the TUT’s
    network
•   There are a series of programs that can receive and
    play the streams, both for Windows and Linux
    platforms (e.g. NetFilter)

                         Multimedia Systems
Conclusions

• Multicast becomes more and more a necessity
• Multicast improves network performances,
    respectively the costs
•   It is easy to configure the network (routers, switches)
    to support multicast
•   In the future, more and more applications will
    become multicast-dependent
•   Multicast has yet to prove it’s impact on our
    networking

                        Multimedia Systems
MPEG-4 over
    IP
OUTLINE

  • MPEG-4 Systems

  • Transport Protocols for MPEG-4 delivery

  • Issues of “MPEG-4 over IP”

  • Conclusions

  • References




                        Multimedia Systems
Introduction

• MPEG (Moving Picture Experts Group);

• MPEG-1  standard on which Video-CD and MP3 are based;

• MPEG-2  standard on which Digital Television set top boxes and DVD are
   based;

• MPEG-4  standard for multimedia for the fixed and mobile web;

• MPEG-7  standard for description and search of audio and visual content;

• An “IP (Internet Protocol) address” uniquely identifies a node, a device or host
   connection on an IP network (or TCP/IP);


                                 Multimedia Systems
   Carriage of MPEG-4 contents over IP
   Networks
• MPEG-4 is a standard designated for the representation and delivery of
   multimedia information over a variety of transport protocols;

• MPEG-4 includes:
    –   Interactive scene management;
    –   Visual & Audio representations;
    –   Functional systems (multiplexing, synchronization);
    –   Object descriptor framework;


• Transfer method for MPEG-4 over IP:
    – In context with specific IP packets;
    – Multiplexed in MPEG-4 Flexmux (carried in IP packets);
    – Multiplexed in MPEG-2 TS (carried in IP packets);

                                 Multimedia Systems
Streaming Media Formats




             Multimedia Systems
Example of MPEG-4 over IP




              Multimedia Systems
Example of MPEG-4 scene




             Multimedia Systems
Object-based compression and delivery




            Multimedia Systems
HTTP Transport Protocol

• It is a very simple way to stream media files;

• The wire format is the same as the file-format storage;

• Arbitrary MPEG-4 Intermedia files cannot be streamed directly using HTTP,
   because of the “loose” in ordering the objects, and possible cross-references
   within the media file;

• Live streaming for Intermedia files can also be supported using proprietary
   methods;




                                Multimedia Systems
Media Control Protocols
•   In order to enable full streaming systems, a media control protocol needs to
    be defined to support the following features:

    1.   Seeking:
         – Forward;
         – Rewind;
         – Skip.

    2.   Bandwidth Scalability

    3.   Live Streaming




                                 Multimedia Systems
MPEG-4 Systems
• In MPEG-4 Systems, the transport of streams is divided in 4 layers:

    – Compression Layer: includes elementary (raw) media streams (audio, video,
      etc.).

    – Synchronization Layer (SL): Adds a header to each unit of an elementary
      stream, which includes time stamps, reference to a clock elementary stream, and
      identification of key frames (RandomAccessPoint). This is similar to the task of
      RTP in IP networks. However, SL does not contain payload type (like RTP), and
      does not contain the Elementary Stream. In addition, an SL packet does not
      contain an indication of its length, so it must be framed by a lower-level protocol
      such as FlexMux or RTP.

    – FlexMux Layer: Groups elementary streams according to common attributes, such
      a QoS requirements. This is very simple multiplexing protocol, but also very low
      overhead.
    – TransxMux Layer: This is the actual transport protocol, such as RTP/UDP, MPEG-
      2, etc. MPEG-4 does not define its own transport protocol, but assumes the
      application relies on an existing transport protocol. The FlexMux Layer is optional,
      but the Synchronization Layer is always present.

                                   Multimedia Systems
TCP/IP & SL-packet over UDP/IP
• TCP/IP:
   – Not suitable for real-time transfers (high delays and causes jitter, it was
     created for reliable transmission over timely delivery);

   – Does not support multicast;

   – Congestion control mechanism not suitable for AV media;


• SL-packet over UDP/IP:
   – SL provides: Timing & Sequence numbering;

   – UDP provides: Multiplexing, Length field, Checksum service;

   – SL+UDP may be used like a transport protocol for AV media;

                                Multimedia Systems
 Problems of SL/UDP/IP
• No other media stream can be synchronized with MPEG-4 data carried
   directly over UDP;

• The dynamic scene and session control concepts cannot be extended to non
   MPEG-4 data;

• No defined technique for synchronizing MPEG-4 streams from different
   servers;

• Streams from different servers may collide (their sources may become
   unresolvable at destination) in a multicast session;

• Mechanisms need to be defined to protect sensitive MPEG-4 data (RTP
   supports FEC);

• A feedback channel must be defined for quality control;
                                 Multimedia Systems
 RTP & RTCP
• RTP = Real-time Transport Protocol;

• RTCP = Real-time Transport Control Protocol;

• A session consists of an RTP/RTCP pair of channels

• Usually works over UDP/IP (can work with other protocols also);

• RTP supports:
    –   Multicasting;
    –   Payload type identification;
    –   Time stamping;
    –   Sequence numbering;
    –   Delivery monitoring;
    –   From UDP (Multiplexing, Length field, Checksum service);


                                   Multimedia Systems
     RTP
• RTP Problems:
    – It does not support the timely delivery of data or any other QoS guarantees;
    – It does not guarantee delivery, so packets may be delivered out of order or get lost
      (no mechanism to recover from packet loss);


• Time Stamp (TS):
    – Place incoming packet in correct timing order
    – Initial values are picked randomly and independently for each RTP stream;
    – Increase in time indicated by each packet;


• Sequence Number (SN):
    – Detect packet loss;
    – Increase by one for each packet;


• For video frame that is split into multiple RTP packets: they share the same
   TS but use different SN;

                                    Multimedia Systems
 RTP Characteristics
• RTP can map only one source stream onto RTP session:
    – Multiplexing causes problems;
    – For scale coding, each layer must have its own RTP session and multicast group;


• Within each RTP session, source can change its data format over time;

• It allows FEC (Forward Error Correction);

• Synchronize across different media streams;

• Provide feedback on the quality of data using packet counts;

• Identify and keep track of participants;



                                  Multimedia Systems
 MPEG-4 over RTP/UDP/IP
• Easiest is to wrap the MPEG-4 SL packet in an RTP packet:
    – High overhead: two full headers;
    – RTCP may not provide enough control for the MPEG-4 stream;


• Several types of MPEG-4 payloads are being defined by the IETF for different
   ESs;




                                 Multimedia Systems
RTP ES & SL payload restrictions
• RTP packetization is not media aware:
    – No unique scheme can be defined, need a payload definition per payload type (not
      practical);
    – This may require the definition of new session and scene description mechanisms
      to deal with all the flows;


• Common restrictions:
    – RTP timestamp corresponds to composition time stamp (CTS) of MPEG-4 stream;
    – Packets should be sent in decoding order;
    – Streams can be synchronized using RTCP;


• Map SL stream onto RTP session:
    – SL header is optional;
• Reduced SL headers does not include:
    – Sequence number (mapped to RTP header);
    – Composition Time Stamp (mapped to RTP header);


                                  Multimedia Systems
   Streams & Media Control in MPEG-4

• Multiple Strems inMPEG-4:
    – Port consuming:
       • Each AV contains one or more streams;
       • Each stream needs one RTP session;
    – Potential solution:
       • Selective bundling of ESs-FlexMux -> define a multiplexed MPEG-4 payload (may have to
           be defined for multiple payload types);
         • Generic RTP multiplexing for use with MPEG-4, under development by IETF.


• MPEG-4 Media Control:
    – Remote interactivity: add or delete a stream, etc.
    – Media control channel allows renegotiating in time the available network and
      processing resources;
    – Must have an efficient signaling protocol that can handle such messages;




                                     Multimedia Systems
 Media Control Framework


• To allow a client and one or more servers to exchange types of control
   messages and also allow for peer to peer exchange between two or more
   clients, the framework requires several components:

    – A description of the stored or live presentation;

    – A set of protocols that can provide proper services for the back channel message
      delivery;

    – A set of protocols that can allocate resources for the involved hosts and networks;




                                     Multimedia Systems
Components of media control (1)


• Presentation Description:

   – The client needs to refer to the description of a presentation that
     expresses the temporal and static properties of the presentation itself;

   – Must include information about the media, location of the media, etc.

   – Should provide multiple description instances of the same presentation so
     that the client can specify a given combination that fits its
     needs/capabilities – the client is the orchestrator of the presentation and
     the server is participating;



                                Multimedia Systems
Components of media control (2)


• Client and Server State Representations:

   – Out of band signaling is used: the data streams and the control
     information are carried over separate channels using different protocols,
     each best suited to their needs and modes of operation;

   – As the media streams may be modified by the end user, the server needs
     to a state if the streams status for each client it is serving;

   – The client has to keep track of all the participating streams;




                                Multimedia Systems
Components of media control (3)


• Basic Media Control Messages:

   – A multimedia system should have access to control messages ranging
     from remote VCR functions such as stop, play, fast forward and fast
     reverse, to messages generated in response to user actions to modify the
     presentation of a given object stream such as add or remove or alter, etc.

   – The basic control functionality relates to presentation and stream set-up:
     play, stop, pause, teardown and recording;




                               Multimedia Systems
      Real Time Streaming Protocol (RTSP)

• It is an application level protocol that provides an extensible framework to
    enable controlled delivery of real-time data, such as audio & video;
•   It can be transported over UDP, TCP and is designated to work with RTP and
    HTTP;
•   Provide support for bidirectional communications (frame level timing for
    remote video editing);

• RTSP does:
     – Control the transmission of media stream;
     – Use out-of-band signaling;


• RTSP does not:
     – Define compression schemes;
     – Define how AV is encapsulated;
     – Define how to buffer;

                                   Multimedia Systems
 MPEG-4 and RTSP
• From DMIF’s perspective, RTSP is an application alongside MPEG-4
   systems;

• The RTSP client and server interact with the MPEG-4 systems;

• The RTSP client and server control the streams through the DAI by an RTSP-
   DMIF interface;

• The interface is kept very simple by limiting it to field mapping between the
   RTSP fields and the DAI primitive parameters;

• The RTSP client server interactions are used to control the MPEG-4
   elementary streams;




                                 Multimedia Systems
 Session Initiation Protocol (SIP)
• IETF Family of Session Protocols:
    – Session Description Protocol (SDP);
    – Session Announcement Protocol (SAP);
    – Session Initiation Protocol (SIP);


• SIP:
    –   Two basic components: user agent & network server;
    –   Independent of lower layer protocols;
    –   Extensible to be application specific;
    –   Gaining widespread use in IP telephony;


• MPEG-4 and SIP:
    – Unique ability to control different media types within a single session  Multiple
      stream transmission in one network session;
    – User Agent model fits in well with an MPEG-4 Client/Server model (point-to-point
      communication);


                                    Multimedia Systems
    Toolboxes for transmitting MPEG-4 over
    internet

• RTP  transport of audio/video/… data, quality-of-service feedback;

• RTSP  very simple media control of streams;

• SIP  inviting people, media servers to sessions – telephony and streaming
   audio/video;

• HTTP, SDP  retrieve media descriptions;




                               Multimedia Systems
 Issues
• Encapsulation of MPEG-4 Sync layer packetized stream:
    – IEC/ISO 14496-8, framework still in revision;
    – Lots of issues still remain: time axis, buffer management, etc…


• Interactivity between application and End User:
    – Description of MPEG-4 content;
    – Initialization of an MPEG-4 session;


• SIP and IPC (Inter Process communication):
    – How to describe the dynamic process of channel (stream) setup and release?
    – What control information is necessary and how to transport it?


• Transport and IP QoS:
    – Must define a mapping mechanism among the different QoS mechanisms:
      transport QoS (not available yet), network QoS, etc.


• And much more…
                                   Multimedia Systems
 Conclusions

• MPEG-4 is here in a limited fashion;

• We will see a marked growth in MPEG-4 products as chip sets become more
   readily available;

• Simple basic MPEG-4 service is not a problem;

• There is a lot of ongoing research on how to deliver MPEG-4 content over IP-
   based networks;

• The extended version still requires a lot more work.




                                Multimedia Systems
 References
• Multimedia Systems, Standards, and Networks, edited by Atul Puri and
   Tsuhan chen, publ. Marcel Dekker, Signal Processing and Communications
   Series;

• Magda El-Zarki, Video Over IP, IEEE Infocom 2001, April 2001.

• Standards for Multimedia Streaming and Communication over Wireless
   Networks v1.0, by Emblaze Research, July 2000.

• Haining Liu, Xiaoping Wei, Magda El Zarki, A transport infrastructure
   supporting real time interactive MPEG-4 Client-Server Applications over IP
   networks, IWDC 2001, pp. 401-412.




                                Multimedia Systems
Windows Media
Microsoft® Windows Media™

• a set of digital media components and
  features for personal computers and
  consumer appliances
• is fueling a revolution in how news,
  information, and entertainment is
  distributed and experienced



                 Multimedia Systems
The Beginning
• started with the personal computer and
    streaming media over the Internet or corporate
    network
•   provided for the first time, truly interactive, on-
    demand audio and video
•   though the quality over analog modems was
    constrained, users were intrigued and satisfied
    with capabilities like news and training on-
    demand, international radio, and Web-only
    event broadcasts.

                       Multimedia Systems
The Present and Future
• several key initiatives that have already started
  to broaden the impact of streaming media on
  the consumer and the worker, the media and
  the IT industries:
   –   Broadband Internet
   –   Digital Music
   –   Consumer Electronics
   –   Business
   –   E-comerce

                        Multimedia Systems
Broadband Internet

• DSL and cable connected homes has
  paved the way for the delivery of CD
  quality music and near-broadcast quality
  video
• need for high speed Internet access for
  high quality video and rich interactivity



                  Multimedia Systems
Digital Music

• the music industry is at the forefront of
  the digital media revolution
• providing CD-quality playback
• increase the number of listeners
• protect and distribute content
• allow for widespread compatibility with
  other digital consumer devices

                  Multimedia Systems
Consumer Electronics
• ensure that the digital media revolution extends
    beyond the PC!
•   media throughout homes, in cars, while jogging
•   a whole suite of additional Windows Media
    compatible consumer electronics devices, will
    soon be on the market, that span digital stereos,
    car stereos, and advanced television set top
    boxes


                      Multimedia Systems
Business
• Companies are rapidly discovering the
 benefits of streaming media in their
 organizations:
  – virtual company meetings
  – "just-in-time" learning
  – ability to react to changing business
    conditions quickly with immediate
    communication to employees, partners and
    customers

                  Multimedia Systems
E-commerce
• rapid growth in usage of digital media for both
    consumer and business applications
•   content providers are looking to move from
    experimentation to revenue generation as
    quickly as possible
•   enables content providers to manage, deliver,
    and sell Pay-Per-Download and Pay-Per-Stream
    content with Windows Media™ over the Internet


                     Multimedia Systems
Key Features of Windows Media
•   Highest Quality Audio
•   Fast video encoding
•   Scalable to Full Screen
•   Windows Media On-Demand Producer
•   Intelligent Streaming
•   Advanced Compression Technologies
•   Integrated with other Microsoft Products
•   Digital Rights Management
•   Microsoft Producer

                      Multimedia Systems
Windows Media Components

• Windows Media Player
• Windows Media Content Creation Tools
• Windows Media Content Editing Tools
• Windows Media Services




                Multimedia Systems
Windows Media Player
• play audio and video in most popular formats
• read and perform commands scripted in an .asx
    (ASF Stream Redirector) file
•   receive script commands, markers, and
    metadata, such as clip title, author, and
    copyright
•   render Windows Media broadcasts and on-
    demand content for viewing live news updates
    on the Internet
•   Play movie clips and music videos on a Web site

                     Multimedia Systems
Windows Media Content Creation
Tools
• used to create ASF content:
  – Windows Media Encoder
  – Windows Media On-Demand Producer
  – Presentation Broadcasting
  – Windows Media Author
  – VidToASF
  – WavToASF


                 Multimedia Systems
Windows Media Content Editing
Tools
• manage and edit your .asf files:
  – indexing
  – checking
  – chopping




                  Multimedia Systems
Windows Media Services

• used to send audio and video content, by
  unicast and multicast, to clients
• control number of streams played
• monitors clients connected to publishing
  points




                 Multimedia Systems
Inside Windows Media - DirectX
• advanced suite of multimedia APIs (application
    programming interfaces) built into Microsoft
    Windows operating systems
•   provides a standard development platform for
    Windows-based PCs by enabling software
    developers to access specialized hardware
    features without having to write hardware-
    specific code
•   DirectX was first introduced in 1995 and is a
    recognized standard for multimedia application
    development on the Windows platform

                      Multimedia Systems
DirectX Usage

• running and displaying applications like
  games that are rich in real-time full-color
  3-D graphics
• movies, video presentations
• music, surround sound
• playing network games


                  Multimedia Systems
DirectShow Overview
• DirectShow is the streaming media component
    of DirectX
•   enables the high-quality capture and playback of
    multimedia streams such as AVI, MP3, and WAV
    files
•   with DirectShow you can create DVD Players,
    Video Editing Packages, Converters, MP3 Players
    and Encoders, and other video/audio
    manipulation applications.

                      Multimedia Systems
DirectShow Goal
• design goal is to simplify the task of creating
    multimedia applications on the Windows
    platform by isolating applications from the
    complexities of data transports, hardware
    differences, and synchronization issues
•   to achieve the throughput necessary for
    streaming video and audio, DirectShow uses
    DirectDraw and DirectSound to render data
    efficiently to the system's sound and graphics
    cards

                      Multimedia Systems
DirectShow relationship with other
components




              Multimedia Systems
DirectShow Architecture
• DirectShow uses a modular architecture in which
  operating system components called filters can be mixed
  and matched to provide support for many different
  scenarios.
• DirectShow includes filters that support cutting-edge
  multimedia capture and tuning devices based on the
  Windows Driver Model (WDM) as well as filters that
  support legacy Video for Windows (VfW) capture cards
  and older codecs written for the Audio Compression
  Manager (ACM) and Video Compression Manager (VCM)
  interfaces.


                      Multimedia Systems
Filter Overview
• special DLL file (.ax)
• create with Microsoft Visual Studio
• based on COM (Component Object Model)
   – getting a pointer to the interface
   – release the pointer after you are done Object Model
• implements standard interfaces
• input and output pins




                            Multimedia Systems
Filter mixing
•   source filters (file, local network, internet)
•   splitter filters (MPEG2 Demux)
•   audio/video (de)compressors filters (MP3, DivX)
•   audio/video renderer filters (FullScreen, DirectSound)




                         Multimedia Systems
Filter’s Pins

• interconnects two filters
• input and output pins
• link between two filters: one-to-one
• responsible for
  – negotiation of media transferred through
  – data exchange
  – synchronization

                   Multimedia Systems
Filter Graph Manager

• all DirectShow applications use this object
  at some point
• this object controls the filter graph
• controls the data flow in the filters
• simple API
  – addFilter
  – run, stop, and pause

                   Multimedia Systems
References

• Microsoft
  www.microsoft.com
• Windows Media
  www.windowsmedia.com
• MSDN (Microsoft Developer Network)
  msdn.microsoft.com



                Multimedia Systems

				
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