Mmc unit i summary
- 1. UNIT I Multimedia Communications -Introduction-Multimedia Networks-Multimedia Applications-Applications and networking terminology- Audio compression and Video Compression INTRODUCTION • Multi: more than one • Medium (singular): middle, intermediary, mean • Media (plural): means for conveying information • Definition1: The term "multimedia" is used to indicate that the information/data being transferred over the network may be composed of one or more of the following media types: 1.Text:IncludesbothUnformattedText - comprisingstringsofcharactersfrom a limited character set and Formatted Text - comprises strings as used for the structuring, access, and presentation of electronic documents. 2. Images: Includes Computer Generated Image- comprising lines, curves, and circles, and Digitized Images of documents and pictures. 3. Audio: Includes both low-fidelity speech - as used in telephony and high- fidelity speech - stereophonic music as used with compact discs. 4. Video: Includes short sequences of moving images (also known as video clips) and complete movies/films. • Definition2:Multimedia is anycombination of text, art, sound,animation, and video. Itis delivered to the user by electronic or digitally manipulated means. A multimedia project development requires creative, technical, organizational, and business skills. • Definition3: Multimedia is the presentation of a (usually interactive) computer application, incorporating media elements such as text, graphics, video, animation and sound on computer. Multimedia is any combination of • text, • graphic art, • sound, • animation, • video, delivered by computer or electronic means The Basic Elements of Multimedia • Text • Graphic • Animation • Video • Audio
- 3. Characteristics of a Multimedia System • A Multimedia system has four basic characteristics: • Multimedia systems must be computer controlled. • Multimedia systems are integrated. • The information they handle must be represented digitally. • The interface to the final presentation of media is usually interactive. Multimedia Application • Presentation With the help of multimedia, presentation can be made effective. • E-books Today, books are digitized and easily available on the Internet. • Digital Library The need to be physically present at a library is no more necessary. Librariescan beaccessedfromthe Internetalso. Digitization has helped libraries to come to this level of development. • E-learning Today, most of the institutions (public as well as private both) are using such technology to education people. • Movie making Most of the special effects that we see in any movie, is only because of multimedia technology. • Video games Video games are one of the most interesting creations of multimedia technology. Video games fascinate not only the children but adults too. • Animated films Along with video games, animated film is another great source of entertainment for children. • Multimedia conferencing People can arrangepersonalas well as business meetings online with the help of multimedia conferencing technology. • E-shopping
- 4. Multimedia technology has created a virtual arena for the e-commerce. • Entertainment – Games – Interactive TV – Post production of movie and music • Residential services – Video-On-Demand – Video phone, – A/V conferencing – Home shopping Multimedia applications may involve either of the following: 1. Person-to-Person communications or 2. Person-to-System communications Person-to-Person communicates using suitable Terminal Equipment (TE) Person-to-System communications: 1. Person interacts with the system using suitable Digital device like workstation or multimedia personal computer (PC). 2. These Digital device are located either in homes or offices. 3. Basically system is a server containing a collection of files or documents each comprising digitized text, images, audio, and video information either singly or integrated together in some way alternatively It may also contain - a library of digitized movies/videos. 4. User interacts with the server by means of a suitable selection device connected to the Set-top box (STB) associated with a television or modem used with the computers. MULTIMEDIA NETWORKS • Five basic types of communication networks are used to provide multimedia communication services: 1. Telephone networks. 2. Data networks. 3. Broadcast television networks. 4. Integrated services digital networks. 5. Broadband multiservice networks. • 1,2, and 3 networks are initially designed to providejust a single type of service as listed as below: 1. Telephone networks: telephony 2. Data networks: data communications 3. Broadcast television networks: broadcast television • 4, and 5 networks: Designed from theoutsetto providemultiple services. Telephone networks • Public Switched Telephone network (PSTNs) is the world's collection of interconnected voice-oriented public telephone networks. • Designed to provide a basic switched telephone service.
- 5. • 'Switched': Term is used to indicate that the subscriber can makea call to any other telephone that is connected to the total network. • Initially such networks spanned just a single country later, telephone networks of different countries were interconnected so, that they now provide an international switched service. • Main components of the network are shown in the Fig below. • Local Exchange/End Office: telephones located in the home or in a small business are connected directly to their nearest LEs. • Private Branch Exchange (PBX): i. Telephones located in the medium or large office/site are connected to a PBX or Private switching Office. ii. Provides a (free) switched service between any two telephones - that are connected to it. iii. Connected to its nearest LE (public), which enables the telephone that are connected to the PBX also to make calls through a PSTN. • Cellular Phone Networks: Been introduced which provide the similar service to the mobile subscribers by means of the handsets that are linked to the cellular phone network infrastructure by radio. • MSC (Mobile Switching Center): it's theswitch used in the cellular phone network Like the PBXsalso, connected to a switchingofficein a PSTNwhich,enables both sets of subscribers to make calls to one another. • IGE (International Gateway Exchange): route and switch the international calls. • Access circuits: link the telephone handsets to a PSTN or PBX were designed to carry the 2-way analog signals associated with a call
- 6. Data networks • Designed to provide basic data communication services such as e-mail and general file transfers. • User equipment - connected to data networks: are the computers such as a PC, a workstation, or an e-mail/file server. • Two widely deployed types of data networks: 1. X.25 network and 2. Internet. • X.25 network: operational mode is restricted to relatively low bit rate data applications. Hence, unsuitable for most multimedia applications. • Internet: Made up of a vast collection of interconnected networks all of which operate using the same set of communication protocols. • Communication protocol: an agreed set of rules that are adhered to by all communicating parties for the exchange of information. • Rules define the sequence of messages that are exchanged between the communication parties and the syntax of these messages. • By using,thesamesetof communication protocols:allthe computersthat are connected to the Internet can communicate freely with each other irrespective of their type or manufacturer this is the origin of the term "open systems interconnection". • Figure below shows a selection of the different types of interconnected network • User at home or in a small business access to Internet is through an intermediate: ISP (InternetService Provider) network normally, this type of user wants access to the Internet intermittently the user devices are connected to the ISP network either through a PSTN with modems or
- 7. through an ISDN (Integrated Services Digital Network which provide access at a higher bit rate). • Business user - obtain access through a site/campus network if, the business comprises only a single site or obtain access through an enterprise-wide private network if, it comprises multiple sites. • Colleges and Universities In the case of a single site/campus: network is known as a (private) LAN (Local Area Network), In the case of sites that are interconnected together using an inter-site backbone network to provide a set of enterprise-wide communication services network is known as an enterprise-wide private network Providing communication protocols used by all the computers connected to the network are the same as those defined for use with Internet. • Enterprise network (Intranet): all internal services are provided by using the same set of communication protocols, as those defined for the Internet. • IBN (Internet Backbone Network): different types of network are all connected to it through an interworking unit called gateways. • Gateways (Router): an interworking unit connects IBN and the different types of network responsiblefor routing and relaying all messages to and from the connected network hence, also called as a router. • Packet mode: all data networks operate in this mode. • Packet: container for a block of data and has head in which, address of the intended recipient computer (which is used to route the packet through the network). Broadcast Television Networks • Designed to supportthe diffusionof analog television and radio programs throughout wide geographical areas. • Cable distribution network used as broadcastmedium, normally in large town or city. • Satellite network (Terrestrial broadcastnetwork): broadcastmedium for large areas • Digital television services have become available. • Low bit rate channel for interaction purposes - with digital television services, provide a range of additional services (like games, home shopping, and etc.,).
- 8. Cable distribution network: • provide basic broadcastradio and television services access to the range of multimedia communication services that are available with both PSTN and Internet. • Cable television, in which the signal is carried to the receiver through a cable General architecture of a cable distribution network: • Consist of set top box : attached to the cable distribution network Provides: 1. Control of the television channels - that are received. 2. Access to other services. • Ex.: Cable modem: integrated into the STBprovides a low bit rate channel and a high bit rate channel from the subscriber back to the cable head end. • Low bit rate channel: used to connect the subscriber to a PSTN. • High bit rate channel: used to connect the subscriber to the Internet. Satellite and terrestrial broadcast networks: • television signalis transmitted to the receiver from an overhead satellite • integrated into the STB provides the subscriber with an interaction channel hence, enhancing the range of services is the origin of the term "interactive television". Integrated Services Digital Networks • Started to be deployed in early 1980s. • It is a telephone network based infrastructure that allows the transmission of voice and data simultaneously at a high speed with greater efficiency. • It is a circuit-switched telephone network system, but it also provides access to packet switched networks that allows digital transmission of voice and data.
- 9. • This results in potentially better voice or data quality than an analog phone can provide. • The key feature of ISDNis that it integrates speech and data on the same lines, adding features that were not available in the classic telephone system. • ISDNprovides simultaneous voice, video, and text transmission between individual desktop videoconferencing systems and group videoconferencing systems. ISDN Services • Voice calls • Facsimile • Videotext • Tele-text • Electronic Mail • Database access • Data transmission and voice • Connection to internet • Electronic Fund transfer • Image and graphics exchange • Document storage and transfer • Audio and Video Conferencing • Automatic alarm services to fire stations, police, medical etc. Types of ISDN • The ISDN has several kinds of access interfaces such as − • Basic Rate Interface (BRI) • Primary Rate Interface (PRI) • Narrowband ISDN • Broadband ISDN Basic Rate Interface (BRI) • There are two data-bearing channels (‘B’ channels) and one signaling channel (‘D’ channel) in BRI to initiate connections. • The B channels operate at a maximum of 64 Kbps while the D channel operates at a maximum of 16 Kbps. • commonly used by smaller organizations or home users or within a local group, limiting a smaller area.
- 10. Primary Rate Interface (PRI) • used by enterprises and offices • consists of a D channel and T-carrier or T1 in the US, Canada and Japan countries consisting of 23 data or bearer channels and one control or delta channel, with 64kbps speed for a bandwidth of 1.544 M bits/sec. Narrowband ISDN • carries voice information which uses lesser bandwidth in a narrow band of frequencies. Broadband ISDN • The broadband ISDNcommunication is usually made using the fiber optic cables. • speed is around 2 MBPS to 1 GBPS. Broadband multiservice networks • Broadband: term used to indicate the circuits associated with a call could have bit rates in excess of the maximum bit rate of 2Mbps 30X64kbps provided by an ISDN. • B-ISDN (Broadband Integrated Services Digital Networks): alternate names for broadband multiservice networks since, were designed to be an enhanced ISDN. TYPES OF MULTIMEDIA APPLICATIONS 1. Interpersonal communications. 2. Interactive applications over the Internet. 3. Entertainment applications. Interpersonal communications • May involve speech, image, text, or video. • Interpersonalcommunications may involvesingletype or integrated two or more type of media involved: 1. Speech only 2. Image only 3. Text Only 4. Text and Images 5. Speech and Video 6. Multimedia Speech Only: • Traditionally, involves – speech, telephony. • Service is provided using telephones which are connected either to PSTN/ISDN/Cellular network or PBX. • Multimedia PC with microphone and speakers, if using user can make telephone calls through PC. • Ex.: Voice-mail and Teleconferencing • Voice-mail: Used when the called party being unavailable Spoken messageis then be left in the voicemail boxof the called party Voice mail server, located in the central repository had voice mail boxes, Message
- 11. can be read by owner of the mailbox the next time he, or she contact the server. • Teleconferencing: Calls involve multiple interconnected telephones/PCs. Person can hear and talk to all of the others involved in the call called the conferencecall/teleconference call since, it involves a telephone network or audio conference call which require an audio bridge - a central unit which supports to set up a conference call automatically. • Internet was used to support telephony. Initially, designed to support computer-to computer communications Just (multimedia) PC-to-PC telephony was supported subsequently, extended so that a standard telephone could be used. • PC-to-PC telephone call: Standard addresses are used to identify individual computers connected to the internet are used same way as for a data transfer application. • Thus Telephony overthe Internetis knownasPacket voiceas thenetwork protocol associated with the internet is called the Internet Protocol (IP), Voice over IP (VoIP). Image Only: • Exchange of electronic images of documents is an alternate form of interpersonal communications over PSTN/ISDN known as Facsimile. • Communication involves use of the pair of fax machines one at each network termination point. • Document sending: a circuit is set up through the network in the same way as for a telephone call • Two fax machines communicate with each other to establish operational parameters after, which the sending machine starts to scan and digitize each page of the document in turn both fax machines have an integral modem within them and as, each page is scanned it’s digitized image is simultaneouslytransmitted over thenetwork and as this is received atthe called side a printed version of the document is produced after the last pageof the documenthasbeen sentand received connection through the network is cleared by the calling machine in the normal ways. Text only: • Ex.: E-mail (Electronic mail). • User terminal is normally are normally a PC or a workstation. • Email servers: One or more associated with each network Collectively contain a mailbox for each user connected to that network User can both create and deposit mail his/her mailbox read mail from it. Standard Internet communication protocol used by e-mail servers. Text and Images: • CSCV (Computer-SupportedCooperative Working) application:involves – text and images integrated. • Network used: enterprise network/LAN/Internet. • User terminal is either a PC or a workstation.
- 12. • Shared whiteboard: Window on each person’s display is used as the shared workspace, display comprises integrated text and images. Speech and Video: • Desktopvideoconferencing call: Telephony like: call may involve not just 2 persons and so, terminals/PCs several people each located in their own office. • Used widely in large corporations involving multiple geographically distributed sites to minimize the travel between the various locations. Large corporations of this type have enterprise-wide network to link the sites together MCU (Multipoint control unit) is a Central unit to support the videoconferencing. Videoconferencing server associated with the network used in few cases. • Videoconferencing studios: Specially equipped rooms are used – which contain all the necessary audio and video equipment, comprising of one or more video cameras, a large screen display, and associated audio equipment, all of which are connected to a unit called videoconferencing system. Multimedia: • Multimedia mail: An extension of text-only mail in as much as the basic content of the mail comprises textual information. • Textual information is annotated with a digitized image, a speech message, or a video message • MIME protocol Interactive Applications Over The Internet: • Internet is used to supporta range of interactive applications along with interpersonal communication applications. • Ex.: WWW (World WideWeb) or simply Web server comprises thelinked set of multimedia information servers thatare geographically distributed around the Internet. • Each documentcomprises a linked set of pages and linkages between the pages are known as hyperlinks. · Hyperlinks are pointers also known as references to other pages of the same document or to any other document within the total web. • Hypertext are documents comprising only texts. • Hypermedia are documents comprising multimedia information. • URL (Uniform Resource Locator) is a Document’s unique address which identifies both location of the server on the Internet, wherethe firstpage of the document is stored and also the file reference on the server. • A Standardformatis used forwriting documentsis knownasHTML (Hyper Text Markup Language) and is also used for writing client software to explore the total contents of the web • A Browser is a Client function and there are number of user-friendly browsers availableto explore visited servers and to open up a dialog with a particular server at the click of the mouse.
- 13. • Teleshopping (home shopping)/ Telebanking (home banking) applications: A client may wish not only to browse through the information at a site but also to initiate an additional transaction Server mustprovide additional transaction processing supportfor, say,ordering and purchasing since, this will also often involve financial transaction, more rigorous security procedures are required for access and authentication purposes. Entertainment Applications Entertainment applications can be of 2 types: 1. Movie/video-on-demand 2. Interactive television • Movie/Video-On-Demand: The video and audio associated with entertainment applications must be of a much higher quality/resolution. • Digitized movie/video with sound requires a minimum channel bit rate (bandwidth) of 1.5Mbps. • Hence, network used to support this application, must be either a PSTN with a high bit rate modem or a cable network of this type. • Information stored on the server: collection of digitized movies/videos. MOD (Movie-On-Demand)/VOD (Video-On-Demand): • From suitable menu subscriber is able to browse through the set of movies/videos available and initiate the showing of a selected movie. Subscriber can control the showing of the movie by using similar controls to those used on a conventional VCR (Video Cassette Recorder) i.e., pause, fast-forward, and so on. • Key feature of MOD: a subscriber can initiate showing of a movie selected from a large library of movies at any time of the day or night. Interactive Television: • Broadcast television networks: include cable, satellite, and terrestrial networks. • Basic service of this network is diffusion of both analog and digital television (and radio) programs. • Itis the integration of traditional television technology and data services. • It is a two-way cable system that allows users to interact with it via commands and feedback information. • A set-top box is an integral part of an interactive television system. • Itcan be used by the viewer to select the shows thatthey want to watch, view show schedules and give advanced options like ordering products shown in ads, as well as accessing email and Internet. • Interactive television is also known simply as interactive TV. APPLICATIONS AND NETWORKING Multimedia networking applications
- 14. • Networked multimedia is to build the multimedia on network systems, so differentusersondifferentmachinescan shareimage, sound,video,voice and many other features. • referred to as continuous-media applications. • Classes of MM networking applications: ● Stored streaming ● Live streaming ● Interactive, real-time Stored streaming: • Media stored at source • Clients request on-demand compressed audio or video files that are stored on servers • Transmitted to client • Streaming: client play out begins before all data has arrived ● clients request on-demand compressed audio or video files, which are stored on servers. For audio, these files can contain a professor's lectures, rock songs, symphonies, archives of famous radio broadcasts, as well as historical archival recordings. ● For video, these files can contain video of professors' lectures, full-length movies, prerecorded television shows, documentaries, video archives of historical events, video recordings of sporting events, cartoons and music video clips. ● At any time a client machine can request an audio/video file from a server. ● In most of the existing stored audio/video applications, after a delay of a few seconds the client begins to playback the audio file while it continues to receive the file from the server. ● The feature of playing back audio or video while the file is being received is called streaming. Many of the existing products also provide for user interactivity, e.g., pause/resumeand temporal jumps to the future and past of the audio file. ● The delay from when a user makes a request (e.g., request to hear an audio file or skiptwo-minutesforward) untiltheaction manifests itself at theuser host (e.g., user begins to hear audio file) should be on the order of 1 to 10 seconds for acceptable responsiveness. Characteristics: • StoredMedia:Content is prerecorded,theclient may pause,rewind,fast- forward or index; The time from when a client makes a request until the action manifests itself at the client should be of the order of 1 to 10 seconds • Streaming: Client begins playout of the media after (a shortdelay, maybe zero) it begins receiving the file from server. • ContinuousPlayout: Onceplayoutof themedia begins,it should proceed according to the original timing of the recording; The end-to-end delay constraints for streaming, stored media are typically less severe
- 15. Streaming Live Multimedia ● Examples: ● Internet radio talk show - It is an audio broadcasting service transmitted via the Internet. - Broadcasting radio shows on the internet is usually preferred to webcasting. - It mainly works by Internet radio transmissions. - Internetradio services areusually accessiblefrom anywherein the world - for example, one could listen to an Australian station from Europe or America. ● Live sporting event ● Streaming (as with streaming stored multimedia) ● Playback buffer ● Playback can lag tens of seconds after transmission ● Interactivity ● Fast forward impossible ● Rewind, pause possible! ● This class of applications is similar to ordinary broadcast of radio and television. These applications allow a user to receive a radio or television transmission emitted from any corner of the world. Real-Time Interactive Multimedia ● Allows people to use audio and video to communicate with each other. Applications ● IP telephony(audio) , video conference (Microsoft teams)
- 16. ● Internetphone can potentially providePBX, localand long-distancetelephone service at very low cost. Itcan also facilitate computer-telephone integration (so called CTI), group real- time communication, directory services, caller identification, caller filtering, etc. ● Note that in a real-time interactive audio/video application, a user can speak or move at anytime. The delay from when a user speaks or moves until the action is manifested at the receiving hosts should be less than a few hundred milliseconds. ● End-to-end delay requirements VIDEO COMPRESSION • Video compression technology is a set of techniques for reducing and removing redundancy in video data. • It is a type of compression technique that reduces the size of video file formats by eliminating redundant and non-functional data from the original video file. • Video compression is the process of encoding a video file in such a way that it consumes less space than the original file and is easier to transmit over the network/Internet. Intra-frame Video Compression • Intra-frame compression is a compression applied to still images, such as photographs and diagrams, and exploits the redundancy within the image, known as spatial redundancy. • Intra-framecompression techniques can be applied to individual frames of a video sequence. Inter-frame Video Compression • Inter-framecompression is compression applied to a sequence of video frames, rather than a single image. • Inter-frame compression exploits the similarities between successive frames, known as temporal redundancy that assists in reducing the volume of data required to describe the sequence. Types of frames • I frame (intra-coded) • Coded without reference to other frames • P frame (predictive-coded) • Coded with reference to a previous reference frame (either I or P) • Size is usually about 1/3rd of an I frame • B frame (bi-directional predictive-coded) • Coded with referenceto both previousand futurereferenceframes (either I or P) • Size is usually about 1/6th of an I frame Video standards- Evolution of MPEG • MPEG-1 • Initial audio/video compression standard • Used by VCD’s
- 17. • Target of 1.5 Mb/s bitrate at 352x240 resolution • Only supports progressive pictures • MPEG-2 • Current de facto standard, widely used in DVD and Digital TV • Ubiquity in hardware implies that it will be here for a long time • Transition to HDTV has taken over 10 years and is not finished yet • Different profiles and levels allow for quality control • MPEG-3 • Originally developed for HDTV, but abandoned when MPEG-2 was determined to be sufficient • MPEG-4 • Includes support for AV “objects”, 3D content, low bitrate encoding, and DRM • Inpractice, providesequal quality to MPEG-2at a lowerbitrate, but often fails to deliver outright better quality • MPEG-4 Part 10 is H.264, which is used in HD-DVD and Blu-Ray AUDIO COMPRESSION Why compression is needed?
- 18. Types of Audio Compression