Media Technology I

1. Media Technology I Lecture Notes and Tutorials on: Web : www.staff.city.ac.uk/~raj

2. Aim of this Module • Describe the theory and operation of the major technologies and equipment of relevance to the media and information industries • Introduce you to the multimedia communications and its range of applications and networking infrastructures • Learn about different media types (text, images, speech, audio and video) and applications (VoIP, multimedia electronic mail, interactive television, e-commerce, m-commerce and others)

3. Syllabus • Multimedia Communications - Multimedia information representation - Multimedia Networks (Telephone, Data, Broadcast, ISDN, Broadband) • Multimedia Communications - Multimedia applications (interpersonal communications, interactive applications over the Internet, Entertainment applications) - Application and Networking Terminology (Media types, communication modes, Network types, multipoint conferencing, network QoS, Application QoS)

4. Syllabus • Multimedia Information Representation - Digitization principles (analogueue signals, encoder design, decoder design) - Text (unformatted text, formatted text, hypertext). Images (Graphics, digitized documents, digitized pictures) • Multimedia Information Representation - Audio(PCM speech, CD-quality audio, synthesized audio). - Video (Broadcast Television, Digital Video, PC Video, Video Content)

5. Syllabus • Text and Image Compression - Compression Principles (source encoders and destination decoders, lossless and lossy compression, entropy encoding, source encoding) - Text compression (Arithmetic coding, LZW coding) - Image compression (GIF format, TIF format, digitized documents, digitized pictures, JPEG) • Audio and video compression - Audio compression (Differential pulse code modulation, adaptive differential PCM, adaptive predictive coding, linear predictive coding, MPEG audio coders) - Video compression (Video compression principles, H.261, H.263, MPEG-1, MPEG-2 etc..)

6. Syllabus • Standards for multimedia communications - Reference models (TCP/IP, protocol basics) - Standards relating to interpersonal communications (circuit networks, packet-switched networks, e-mail) • Network management – Network operations centre Performance management, Configuration management, Billing, fault management, security management • Standards for multimedia communications - Standards relating to interactive applications (information browsing, e-commerce, intermediate systems, Java and JavaScript) - Standards for entertainment applications (Movie/Video-on-demand, iTV)

7. Syllabus • Digital Communications - Transmission media (two-wire open lines, twisted-pair lines, coaxial cables, optical fibre, satellites, microwave communications, signal propagation delay) • New multimedia technologies - UpnP - Zigbee - Jini - smart homes - mobile web services - IMS (IP Multimedia Subsystems)

8. Introduction • ‘Multimedia’ means the information transferred is composed of text, images, audio and video - Text (Unformatted and Formatted) - Images (Computer-generated, Digitized, etc.) - Audio (Low-fidelity speech as in telephony and high-fidelity stereophonic music as in CD’s - Video (Moving images and complete movies/films)

9. Introduction • Person-to-person (communication) – Two people communicate through suitable Terminal Equipment (TE) • Person-to-system (Interactive ) – Using multimedia Personal computer or Workstation ( Located at home or in an office)

10. Voice and Data Networks • Public switched telephone networks (PSTNs) – initially designed to provide speech services. However, due to the advances in Digital Signal Processing (DSP) hardware and software now can support multimedia applications • Data networks that initially supported data applications (email and ftp) now support much complex multimedia applications

11. Multimedia Information Representation • Text: Block of characters, each represented by a fixed number of binary digits (bits) known as codeword • Digitized image: Two-dimensional block of picture elements represented by a fixed number of bits • Audio and Video: Type of signal is known as an analogue signal and varies continuously with time (e.g: a telephone conversation can last for several minutes while a movie (audio + video) can last for a number of hours

12. Multimedia Information Representation • Single type of media - basic form of representation of a specific media type used • Mixed media – applications involving text and images or audio and video their basic form is used • Integrated media (text,images,audio,video)- Must convert all the four media into a suitable digital form

13. Multimedia Networks • Telephone Networks - Telephony • Data Networks – Data Communications • Broadcast Television Networks – Broadcast TV) • Integrated Services Digital Networks (ISDN) – Multi service • Boradband Multiservice Networks – Multi service

14. Telephone Networks • PSTN – Now known as Plain Old Telephone Service (POTs) • The term switched means a subscriber can make a call to any other telephone on the ‘total’ network

15. PSTN • PSTN (public switched telephone network) is the world's collection of interconnected voice-oriented public telephone networks, both commercial and government-owned. • It's the aggregation of circuit-switching telephone networks that has evolved from the days of Alexander Graham Bell. • Today, it is almost entirely digital in technology except for the final link from the central (local) telephone office to the user

16. Telephone Networks • Telephones in the home or in a small business are connected directly to their nearest local exchange/end office • Telephones in a large office are connected to a private switching office known as private branch exchange (PBX) • PBX provides free service between two telephones that are connected to it • A PBX is a telephone system within an enterprise that switches calls between enterprise users on local lines while allowing all users to share a certain number of external phone lines. The main purpose of a PBX is to save the cost of requiring a line for each user to the telephone company's central office.

17. Telephone Networks • PBX is connected to the local exchange and this enables phones connected to the PBX to make calls through PSTN too. • Cellular phone networks – Provides service to mobile subscribers • The switches used in a cellular phone network are known as Mobile Switching Centers (MSCs) • International calls are routed to and switched by international gateway exchanges (IGEs)

18. Telephone Networks • Circuit mode – Telephone networks operate in this mode in which a separate circuit is set up through the network for each call for the duration of the call • Access Circuits – Link the telephone handsets to a PSTN or PBX and carry two-way analogue signals associated with a call

19. Telephone Networks • Today with high bit-rate channels in addition to the voice using the same access networks high resolution audio and video can be downloaded from a range of entertainment related servers

20. Data Networks • Designed to provide basic data communication services such as email and general file transfer • Most widely deployed networks: X.25 network (low bit rate data) not suitable for multimedia and the Internet (Interconnected Networks) • Communication protocol: set of rules (defines the sequence and syntax of the messages) that are adhered to by all communicating parties for the exchange of information/data • Packet: Container for a block of data, at its head, is the address of the intended recipient computer which is used to route the packet through the network

21. Data Networks • Open systems interconnections (OSI)-is a standard description or "reference model" for how messages should be transmitted between any two points in a telecommunication network • Access to homes is through an Internet Service provider (ISP) • Access through PSTN or ISDN (high-bit rate)

22. Data Networks • Business users obtain access either through site network or through an enterprise-wide private network (multiple sites) • Universities with single campus use a network known as the Local Area Network (LAN). However bigger universities with more than one campus use enterprise wide network • If the communication protocols of the computers on the network are the same as the internet protocols then the network is known as an intranet (e.g large companies and universities)

23. Data Networks • All types of network are connected using a gateway (router) to the internet backbone network • Router - a router is a device or, in some cases, software in a computer, that determines the next network point to which a packet should be forwarded toward its destination

24. Data Networks • Packet mode – Operates by transfer of packets as defined earlier • This mode of operation is chosen because normally the data associated with data applications is in discrete block format. • With the new multimedia PCs packet mode networks are used to support in addition to the data communication applications a range of multimedia applications involving audio video and speech

25. Broadcast Television Network • Broadcast television networks support the diffusion of analogue television programs to a wider geographical area via a cable distribution network, a satellite network • A cable modem integrated into the STB (set-top-box) provides both a low bit rate channel (connects the subscriber to the PSTN ) and a high bit rate channel (connects to the Internet) from the subscriber back to the cable head-end

26. Broadcast Television Network • A set-top box is a device that enables a television set to become a user interface to the Internet and also enables a television set to receive and decode digital television (DTV) broadcasts. DTV set-top boxes are sometimes called receivers.

27. Satellite/terrestrial broadcast network • In Satellite and broadcast networks by integrating an H-S modem into the STB a range of interactive services can be supported. This is the origin of the term “interactive television”

28. Integrated Services Digital Networks • Started to develop in the early 1980s to provide PSTN users the capability to have additional services • Integrated Services Digital Network (ISDN) in concept is the integration of both analogue or voice data together with digital data over the same network. • ISDN is a set of ITU standards for digital transmission over ordinary telephone copper wire as well as over other media. Home and business users who install an ISDN adapter (in place of a modem) can see highly-graphic Web pages arriving very quickly (up to 128 Kbps). ISDN requires adapters at both ends of the transmission so your access provider also needs an ISDN adapter. ISDN is generally available from your phone company.

29. Digital Subscriber Line (DSL): • DSL (Digital Subscriber Line) is a technology for bringing high-bandwidth information to homes and small businesses over ordinary copper telephone lines. • Assuming your home or small business is close enough to a telephone company central office that offers DSL service, you may be able to receive continuous transmission of motion video, audio, and even 3-D effects. • Typically, individual connections will provide from 1.544 Mbps to 512 Kbps downstream and about 128 Kbps upstream. A DSL line can carry both data and voice signals and the data part of the line is continuously connected. • Access circuit that allows users either two different telephone calls simultaneously or a telephone call and a data network

30. Integrated Services Digital Networks • DSL supports two 64 kbps channels that can be used independently or as a single combined 128kbps channel (additional box of electronics). This is known as the aggregation function

31. Broadband Multi service Networks • Broadband – Circuits associate with a call could have bit rates in excess of the maximum bit rate of 2Mbps – 30X64 kbps – provided by ISDN • Broadband integrated services digital network (B-ISDN) – All different media types are converted in the source equipment into a digital form, integrated togeather and divided into multiple fixed-sized packets (cells)

32. Broadband Multiservice Networks • Broadband – Circuits associate with a call could have bit rates in excess of the maximum bit rate of 2Mbps – 30X64 kbps – prvided by ISDN • Broadband integrated services digital network (B-ISDN) – All different media types are converted in the source equipment into a digital form, integrated togeather and divided into multiple fixed-sized packets (cells)

33. Multimedia Applications • Application that involve multiple media types: - Interpersonal Communications: May involve speech, image, text or video - Interactive Applications over the Internet: Browsing through sales, literature, newspapers, etc. - Entertainment Applications: Movie/Video on demand, interactive television

34. Interpersonal Communications (Speech only) • Traditional interpersonal communication involving speech was provided by using telephones connected to either PSTN/ISDN or PBX hub. • Today multimedia PC equipped with a microphone and speakers can be used to make telephone calls. This technology is known as computer telephony integration (CTI)

35. Advantages of using CTI • The users can create their own private directory of numbers and can initiate a call simply by selecting the desired numbers from the PC screen • Provides access circuit to the network with more capacity known as the bandwidth • Integration of the PC based network services with the telephony is possible

36. Additional services supported by the public and private networks • Voice mail: Used in the event of the called party being unavailable. The voice mail is saved in the server mailbox and can be read by the owner next time they contact the server • Teleconferencing: Involves multiple interconnected telephones/PCs. Each person can talk to all the others involved in the call. This is known as a conference call. A central unit called an audio bridge provides the necessary support to set up the call automatically

37. Additional services supported by the public and private networks • Internet telephony initially supported computer-to-computer communications • Today the technology is extend so that computer-to-telephony is possible

38. Telephony over the Internet • To make a PC-to-PC telephone call the standard addresses that identify the PC on the network are used same as in a data transfer application • However, since the internet operates in a packet mode necessary conversion software and hardware is mandatory in both the PCs. This type of telephony is known as Voice over IP (VoIP) • To make a call using a PC connected to the Internet to a telephone connected to a PSTN/ISDN an interworking unit known as telephony gateway is necessary.

39. Principle of VoIP • Initially the PC user sends a request to make a telephone call to a preallocated gateway using its internet address. • If the user is registered the gateway will request the phone number to establish the call from the PC • On receipt of this the source gateway will initiate a call with the gateway nearest to the called party. • The called gateway then establishes the call to the recipient telephone using its telephone number and the call setup procedures • If the called party answers then a signal is sent back by the recipient gateway to the PC user via the source gateway

40. Image only interpersonal Communication • Fax: Exchange of electronic images or documents over PSTN/ISDN • As shown above this requires use of a pair of fax machines, one at each termination point • Both fax machines have an integral modem within them

41. Image only interpersonal Communication • PC can also be used instead of a normal fax machine • The PC can send an electronic version of a document stored directly within the PCs memory • This requires a telephone interface card and associated software • In addition it is possible to send digitised documents over other enterprise network (LAN interface card and software required)

42. Image only interpersonal Communication Step1: Initially the caller keys in the telephone number of the intended recipient and a circuit is set up through the network Step2: The two fax machines communicate with each other to establish operational parameters Step3: The sending machine starts to scan and digitized each page of the document in turn and is simultaneously transmitted over the network Step4: After the final page has been sent/received the connection through the network is cleared by the calling machine

43. Text only interpersonal Communication • The user terminal is normally a PC or a work station networked • Associated with each network is a server/servers. Each is known as an email server and they contain mailboxes for each user connected to the network • An example of interpersonal communications involving just text is email

44. Text and images • An example of an application that involves both text and images integrated together is computer-supported cooperative working (CSCW) • The network used is Intranet, Internet or LAN

45. Text and images • A distributed group of people working on the same project can share each others display. This is known as shared whiteboard. • The CSCW comprises a central “whiteboard program” and a linked set of subprograms in each PC/workstation with a shared window or workspace (shared whiteboard)

46. Speech and video • An example of this type is video telephony • As can be seen from the figure the terminals/PCs incorporate a video camera in addition to the microphone and speaker • The network must provide sufficient bandwidth to support the integrated speech and video generated

47. Speech and video • Desktop videoconferencing call – Many interconnected PC users in geographically distributed sites can share speech and video between various locations • To support video conferencing a central unit called a multipoint control unit(MCU) is used. This selects a single information stream to send to each participant hence reducing the communication bandwidth

48. Speech and video • Multicasting – In which all transmissions from any of the PCs/workstations belong to a predefined group are received by all the other members of the group • Using multicasting eliminates the need for an MCU unit Note: Only possible when there are few participants involved

49. Many-to-many videoconferencing • As group of people present at each location these rooms must contain audio and video equipments and are known as videoconferencing studios • Each studio will have few cameras, a large-display, and associated audio equipment. These will be connected to a central unit called the videoconferencing system

50. A multimedia email will consist of text, images, audio and video. • Examples of email applications consisting media types other than text are Voice-mail, Video mail and multimedia mail • Voice-mail: With internet-based voice-mail, there is an associated voice-mail server. • The user enters a voice message addressed to the intended recipient and the local recipient’s voice-mail server then relays this to the local recipient the next time he logs in Many-to-many videoconferencing