Video On Demand

CMD2014 – Multimedia System and Technique Assignment 1

Video On Demand. Overviewing these chapter, video-on-demand or VOD is a system that allows user to select and watch or listen to video or audio content on demand. VOD system stream through a magnetic disk drive, allowing viewing in real time. VOD is much similar to ITV(Interactive Television). This VOD system is very acceptable in hotel, cruise ships, hospital and educational segments business. There were many examples of VOD such as the ordering the PPV(Pay-Per-View) movie, video kiosks, game selection, the channel changer and instructional laserdiscs is a consist of VOD. How do VOD function? Download and streaming video on demand systems provide the user with a large subset of VCR functionality including pause, fast forward, fast rewind, slow forward, slow rewind, jump to previous/future frame and many more. These functions are called trick modes. For disk-based streaming systems which store and stream programs from hard disk drive, trick modes require additional processing and storage on the part of the server, because separate files for fast forward and rewind must be stored. Memory-based VOD streaming systems have the advantage of being able to perform trick modes directly from RAM, which requires no additional storage or CPU cycles on the part of the processor. There were 4 characteristics of VOD;  Near VOD (NVOD)  Instantaneous VOD  Live Interactive VOD  True Interactive VOD Near VOD, pay-per-view video technique used by multi-channel broadcasters using highbandwidth distribution such as satellite and cable television. Multiple copies of a program are broadcast at short time intervals providing convenience for viewers, who can watch the program without needing to tune in at a scheduled point in time. The navigational function also include video menu screens, keypad set-top devices, printed schedules, and many more. By using digital storage and transmission technology, this transition in NVOD give better quality by eliminating noisy satellite feeds. System will offer a larger selection of programming, more reliable, and lower costs. In turn, the same satellite transponders would then be open to offer live programming because the media library will already be on site, digitally stored on the server for near-instant retrieval. Instantaneous VOD, is a subset of NVOD. Instantaneous VOD offering no predetermined start times with a limited number of other options. Such options are VCR-like function, such as pause, replay or fast-forward. The system can start out modest and then grow as capacity demands or feature dictate. The level of quality will be scalable, providing various resolutions depending upon program content. Live Interactive VOD, is a media delivery that is expected to provide a user feedback. This service requires a special type of server and is intend for such programming as live interactive shopping and other special venues such as remote ticket orders or vacation tour planning. True Interactive VOD, is the most advance of all VOD system. In this service, each client/viewer has control overall the programming material. Nothing will be time slotted, as interactive DM0540117 Section 1 Faculty Of Information and Technology

CMD2014 – Multimedia System and Technique Assignment 1

VOD that provide instantaneous and random delivery of media such as forward, backward, restarted or paused in real time. In terms of structure, many hybrid system composed of services bridging any of these described systems and services. In VOD, there comes two way responding rendered systems that will incorporate sophisticated database and demographic tracking capabilities. The system eventually have advertising for the specific viewer, in the same fashion that you’ll have program selectability. The commercial will be more targeted to the viewer interest. Software and delivery packages consist in distribution networking will enable the creators of content to directly serve the audience they wish to target. It is possible that the desktop applications now being used for interactive content creation will be further expanded or customized to particular VOD system so that producers can develop applications specific for client demographics.

Interactive Television. Interactive television represents a continuum from low interactivityto moderate interactivity such as simple movies on demand without player controls, and high interactivity in which an audience member affects the program being watched. The most obvious example of this would be any kind of real-time voting on the screen, in which audience votes create decisions that are reflected in how the show continues. As new products in videotape technology formed such as the DVCPRO, DV-CAM, DV, BetacamSX and other, broadcaster continued to discover how far they must continue to explore, DM0540117 Section 1 Faculty Of Information and Technology

CMD2014 – Multimedia System and Technique Assignment 1

evaluate and define where their business might be headed. Video Server seemed to be the answer. Expensive, changing too fast, and mired in a mixture of formats and other digital frustrations. The new player was the PC, video is watchable but it still cannot replace the old fashioned family room TV set. The Web-TV emerged, trying to be the first link between television viewing and the internet. Web-TV also wasn’t successful as it hoped to be. Comparing the TV and PC, the evolution of entertainment delivery devices shows a marked and different prespective. Changes occurred in a short time frame of just over 30 years from the mid 1970’s. For example the CD players had replace the phonograph, the merge of laserdisc, Screen Projector, and DVD. But still internet becoming the success, but the biggest different is in ‘how you view the medium. We can view and enjoy TV set from most every position in the living room, but you can’t really play Myst from eight-feet away on a 15inch monitor. Television Audio hasn’t moved much also since the 80’s. The SAP (Secondary Audio Program) channel never really caught on. In conjunction of marketing, some of the manufactures took a shortcut and mixed SAP and the primary stereo channel together, rendering the broadcaster’s attempts to provide additional information virtually worthless. If interactive TV needs to be successful, one of the necessary and essential elements must be navigational feature set. The TV set has two basics control such as the volume and channel changer, but the PC is different altogether. The PC offering a keyboard, a mouse, and a joystick as a control of interface set. Will the user of ITV be satisfied if these element of computer being combined to improve the quality of ITV? These are the items that is being researched as it get closer to ITV’s rebirth. The explosion of the internet has changed direction for many media related to delivery platforms. It has and still is a tremendous proving ground for what the consumer accept is what they willing to pay for. The internet offers more interactively than ITV, but the internet still suffers from a bandwidth clogging and a one-to-one visual interface. Television has always offered these two significant differences.

In year 2000, a set top box is still an experiment. Most interaction that one can achieve with a set top is the electronic program guide built into the direct home satellite broadcasters. Through a land line connection, pay-per-view near VOD at least provides the end user with some feeling of interaction. If these element such as games, quiz shows, video-on-demand, viewer voting or pools for determining on a mass basis the outcome of a program, can made ITV to be more ‘interactive’. There are also a third form of ITV called ‘internet TV’, where the specific web-pages are accessible direct from the internet that have been specifically designed and formatted for the larger screen size and limited interface of the television receiver. The example of internet TV is WebTV, OpenTV, Liberate (AOL-TV), and many more.

DM0540117 Section 1 Faculty Of Information and Technology

CMD2014 – Multimedia System and Technique Assignment 1

The Advanced Television Enhancement Forum, an efforts toward content specifications for ITV was formed in

1999. They are making transport

recommendations

and providing

recommendations for bindings between conventional DTV, enhanced and interactive/internet TV. The drive technology PVR is develop by Quantum and called the ‘QuickView’ hard drive, allowing the viewer to take advantage of feature sets the broadcasters have used for years. Viewers can now record and have instant access to programs, skip and repeat segments, have instant recording and playback, plus pause program viewing for personal breaks and resume viewing them without missing a single segment of the program. Stunt features such as instant rewind or fast forward and slow motion are built in. When PVR entered the market, it is striving for acceptance from the consumer and from the broadcaster.

Question 2. ( Define Cryptography. Explain two kinds of cryptosystems; Symmetric and Asymmectric.)

There are many aspects to security and many applications, ranging from secure commerce and payments to private communications and protecting passwords. It is also the practice and study of hiding information. In modern times cryptography is considered a branch of both mathematics and computer science and is affiliated closely with information theory, computer security and engineering. Cryptography is used in applications present in technologically advanced societies such as the security of ATM cards, computer passwords and electronic commerce which all depend on cryptography. Before the modern era, cryptography was concerned solely with message confidentiality conversion of messages from a comprehensible form into an DM0540117 Section 1 Faculty Of Information and Technology

CMD2014 – Multimedia System and Technique Assignment 1

incomprehensible one and back again at the other end, rendering it unreadable by interceptors or eavesdroppers without secret knowledge (namely the key needed for decryption of that message). In recent decades, the field has expanded beyond confidentiality concerns to include techniques for message integrity checking, sender/receiver identity authentication, digital signatures, interactive proofs and secure computation, among others. Cryptography is the science of writing in secret code and is an ancient art of the first documented use of cryptography in writing dates back to circa 1900 B.C. when an Egyptian scribe used non-standard hieroglyphs in an inscription. Some experts argue that cryptography appeared spontaneously sometime after writing was invented, with applications ranging from diplomatic missives to wartime battle plans. It is no surprise, then, that new forms of cryptography came soon after the widespread development of computer communications. In data and telecommunications, cryptography is necessary when communicating over any untrusted medium, which includes just about any network, particularly the Internet.

There are two kind of cryptosystems. The figure 1.0 below shows the cryptosystem.

Figure 1.0 Cryptosystem (Symmetric and Asymmetric)

DM0540117 Section 1 Faculty Of Information and Technology

CMD2014 – Multimedia System and Technique Assignment 1

Symmetric cryptography also known as secret key cryptography, a single key is used for both encryption and decryption. As shown in Figure 1.0, the sender uses the key (or some set of rules) to encrypt the plaintext and sends the ciphertext to the receiver. The receiver applies the same key (or ruleset) to decrypt the message and recover the plaintext. Because a single key is used for both functions.With this form of cryptography, it is obvious that the key must be known to both the sender and the receiver; that, in fact, is the secret. The biggest difficulty with this approach is the distribution of the key. Secret key cryptography schemes are generally categorized as being either stream ciphers or block ciphers. Stream ciphers operate on a single bit (byte or computer word) at a time and implement some form of feedback mechanism so that the key is constantly changing. A block cipher is so-called because the scheme encrypts one block of data at a time using the same key on each block. Generally, the same plaintext block will always encrypt to the same ciphertext when using the same key in a block cipher whereas the same plaintext will encrypt to different ciphertext in a stream cipher. Stream ciphers come in several flavors but two are worth mentioning here. Self-synchronizing stream ciphers calculate each bit in the keystream as a function of the previous n bits in the keystream. It is termed "self-synchronizing" because the decryption process can stay synchronized with the encryption process merely by knowing how far into the n-bit keystream it is. One problem is error propagation; a garbled bit in transmission will result in n garbled bits at the receiving side. Synchronous stream ciphers generate the keystream in a fashion independent of the message stream but by using the same keystream generation function at sender and receiver. While stream ciphers do not propagate transmission errors, they are, by their nature, periodic so that the keystream will eventually repeat. The Data Encryption Standard (DES) and the Advanced Encryption Standard (AES) are block cipher designs which have been designated cryptography standards by the US government although DES's designation was finally withdrawn after the AES was adopted. Despite its deprecation as an official standard, DES is still-approved and much more secure triple-DES variant and remains quite popular; it is used across a wide range of applications, from ATM encryption to e-mail privacy and secure remote access. Many other block

DM0540117 Section 1 Faculty Of Information and Technology

CMD2014 – Multimedia System and Technique Assignment 1

ciphers have been designed and released, with considerable variation in quality. Many have been thoroughly broken. Asymmetric cryptography also known as the Public-key cryptography is a cryptographic approach, employed by many cryptographic algorithms and cryptosystems, whose distinguishing characteristic is the use of asymmetric key algorithms instead of or in addition to symmetric key algorithms. Using the techniques of public key-private key cryptography, many methods of protecting communications or authenticating messages formerly unknown have become practical. They do not require a secure initial exchange of one or more secret keys as is required when using in symmetric key algorithms. It can also be used to create digital signatures. Public key cryptography is a fundamental and widely used technology around the world, and is the approach which underlies such Internet standards as Transport Layer Security and PGP and GPG. The distinguishing technique used in public key-private key cryptography is use of asymmetric key algorithms because the key used to encrypt a message is not the same as the key used to decrypt it. Each user has a pair of cryptographic keys such as a public key and a private key. The private key is kept secret, while the public key may be widely distributed. Messages are encrypted with the recipient's public key and can only be decrypted with the corresponding private key. The keys are related mathematically, but the private key cannot be feasibly (ie, in actual or projected practice) derived from the public key. It was the

discovery

of

such

algorithms

which

revolutionized

the

practice

of

cryptography beginning in the middle 1970s. In contrast, Symmetric-key algorithms, variations of which have been used for some thousands of years, use a single secret key shared by sender and receiver which must also be kept private, thus accounting for the ambiguity of the common terminology for both encryption and decryption. To use a symmetric encryption scheme, the sender and receiver must securely share a key in advance. Symmetric key algorithms are nearly always much less computationally intensive, it is common to exchange a key using a key-exchange algorithm and transmit data using that key and a symmetric key algorithm. PGP, and the SSL/TLS family of schemes do this, for instance, and are called hybrid cryptosystems in consequence.

DM0540117 Section 1 Faculty Of Information and Technology

CMD2014 – Multimedia System and Technique Assignment 1

In additional, there is a third type of cryptography. Cryptographic hash functions are a third type of cryptographic. They take a message of any length as input, and output a short, fixed length hash which can be used in, for example, a digital signature. Cryptographic hash functions are also typically used to provide a digital fingerprint of a file's contents, often used to ensure that the file has not been altered by an intruder or virus. Hash functions are also commonly employed by many operating systems to encrypt passwords.

DM0540117 Section 1 Faculty Of Information and Technology