Subject : multimedia

1. 
   Define multimedia ?
   

1. 
   The conversion of an analog signal into digital form is done using an electronic circuit called an encoder.
   
2. 
   An analog quantity is a physical value that varies continuously over space and /or time.
   
3. 
   Font Size is usually specified in a unit called Point .
   
4. 
   Movies are essentially combinations of images and sounds.
   

1. 
   Note on MULTIMEDIA PRESENTATION AND PRODUCTION
   

The end users who execute and watch the presentation are called viewers or the target audience. A multimedia Production this is carried out by a team of professionals equipped with the required skill and knowledge. These professionals are called developers or authors and the development work is called authoring.

1. 
   Define MULTIPLE MEDIA
   

Third type of media called audio. People have been communicating for years using audio through telephones, radios or walkie-talkies. The other media called video such as television and motion pictures are some of the well known examples.

1. 
   Note on UTILITIES OF MULTISENSORY PERCEPTION
   

• 
  They enrich the set of media which stimulates a given sense. Rich text, graphics and video
  
• 
  They introduce media which stimulates new sense like audio in the form of human speech and music
  

• 
  The interaction with computer system more natural and friendly.
  
• 
  Useful redundancy of information may be possible.
  
• 
  Complementary information presented together may improve memorization of knowledge
  
• 
  Emotional information is easier to convey.
  
• 
  Multisensory system may be of invaluable benefit to users with special needs.
  

1. 
   Note on DIGITAL REPRESENTATION:
   

The real world that we perceive with our means is essentially an analog world, which roughly means “Continuous”. The various phenomena like light, heat, magnetism, sound, electricity all appear as continuous entities without breaks.

Digitization parameters like sampling rate and bit depth decide the final quality of the digital media produced. Theorems like Nyquist’s sampling theorem provide guidelines for choosing these parameters efficiently. Fourier transformation is extensively using din multimedia for converting space/time domain signals into frequency domain and vice versa.

1. 
   Explain ANALOG REPRESENTATION
   

If the signal is also continuous we say that it is analogous to the measured variable. The instruments are called sensors and the signals usually are electrical in nature, because of the ease with which we can manipulate and measured electrical signals.

• 
  The signal delivered by the capturing instrument may take any possible value within the limits of the instrument.
  
• 
  The value can be expressed by any real number in the available range. Analog signals are thus said to be amplitude continuous.
  
• 
  The value of the analog signal cam be determined for any possible value of time or space variable. Analog signals are therefore also said to be time continuous or space continuous.
  

Signal amplitude Positive

Displacement

Mean Position Space or Time

Negative displacement

An analog quantity is continuous over space or time

1. 
   Write the NEED FOR DIGITAL REPRESENTATION
   

Each transistor essentially behaves as a bi-polar switch it can either be ON or OFF. These states of the switches are used to store data. This is actually done each alphanumeric character represented by a combination of 1s and 0s known as ASCII code. And numbers comprise of only 1s and 0s the code is known as binary code. Each of these digits is known as a bit, short for binary digit, while a collection of 8 bits is called a byte.

Files are stored in a specific folder called Fonts under the windows folder. These files are usually in vector format i.e. character description is stored mathematically. Windows calls these fonts as true type fonts because their appearance stays the same on different devices like monitors, printers and plotters and they have extension of TTF.

An alternative form of font files is the bitmap format where each character is described as a collection of pixel.

Font Size and Style:

Font characters have number of sizes. Size is usually specified in a unit called Point (pt). where 1 point equals 1/72 of an inch.

Common styles used are Bold, Italics, Underline, etc., Application package allow changing the horizontal gap between characters called Kerning. and the vertical gap between two lines of text called Leading.

8.Explain about Insertion of text.

INSERTION OF TEXT:

Insertion of a text can be of two ways.

The most common process of inserting text into a digital document is by typing a text using device called Keyboard. Usually a text editing software like Microsoft word is used to control the appearance of text which allows the user to manipulate variables like font , size, style, color etc.

Coping a text from a pre-existing digital document. The existing document is opened using the corresponding text processing program and portion of the text may be selected by using the keyboard or mouse. The copy command the selected text is copied to the clipboard. Paste command is copied from the clipboard into the target documents.

Large text documents covering a number of pages may takes a lot of disk space. We can apply compression algorithm to reduce the size of the file during storage a reverse algorithm must be applied to decompress a file before its contents can be displayed in the screen. A Threee type of compression is used.

This type of coding is intended for applications in which the text to be compressed has known characteristics in terms of character used and the frequency of occurrence. Using fixed length code words compression can be done.

In this method instead of using a single character as a basic of coding operation a string of character is used. So this string of character is held by both encoder and decoder.

This is used fro both spell checking and compression of text. This method allows the dictionary to be built up dynamically by the encoder and decoder for the document under processing.

Unformatted text document created by an editor like notepad on windows platform. It can be used to transfer textual information between different platforms like windows, DOS and UNIX.

It is a native format for storing document created by MS-Word Package. Contain a rich set of formatting capabilities.

There are important characteristics of a multimedia presentation, they are

• 
  Multiple media
  
• 
  Non-linearity
  
• 
  Scope of interactivity
  
• 
  Integrity
  
• 
  Digital Representation
  

Pictures were sub divided into two types: the real world pictures captured by a camera, called images, and the hand drawn pictures like sketches, diagrams and portraits called graphics.

The text, images and graphics are together referred to as statics elements, because they do not change over time. Unlike text and pictures, sound requires audio speakers to be played back and can comprise music, human speech or other sounds effects like breaking glass, falling water etc..,

Movies are essentially combinations of images and sounds. Movies are again divided into two classes: those which depict real world incidents are called motion pictures or motion video and those which depict artificial or imaginary scenarios are called animation.

Non-Linearity:

Non-linearity is the capability of “jumping” or navigating from one point within a presentation to another point without appreciable delay.TV shows and motion pictures are considered linear presentation because the user or viewer has to watch the information being displayed in a pre defined sequences of frames as determined by the producer or creator.

The viewer cannot change the sequences. Devices like video cassette player do9 give us some flexibility during playback of a record video cassette by allowing us to go forward or backward, and starting, stopping pausing the show if required. The tape has to rotate forward or backward to skip the portions.

In multimedia presentation the user can instantly navigate to different parts of the presentation and display the frames in the way she/he chooses without appreciable delays, due to which is called non-linear presentation.

Interactivity elements embedded within the presentation like buttons. Menus items or hyperlinks. A user can also interact with the individual media elements within a presentation. E.g.: click button to start a video sequence within the presentation or pause the background music.

Interactivity is a powerful tool and hopes to achieve much more than simply switching on/off media elements.

Digital representation:

Audio and video cassettes players use media recorded on magnetic tapes in analog format. Magnetic tapes are called Sequential access storage devices i.e., data is recorded sequentially along the length of the tape. This is best done inside a digital computer which stores data on Random access devices like hard disk, floppy disk and compact disc.

Software based programs can be used to edit the digitized media in various ways to improve their appearances and compress files sizes to increase performances efficiency.

Important characteristic of multimedia presentation called integrity. There may be several media types present and playing simultaneously, they need to be integrated or be part of a single entity which is the presentation.

Hardware and software requirements of a multimedia PC can be categorized into two classes.

1. 
   Multimedia playback usually requires smaller amount of resources those which are sufficient for viewing an existing multimedia presentation.
   
2. 
   Multimedia Production generally requires greater and more powerful recourses and should fulfill all requirements for designing and developing a multimedia presentation.
   

• 
  Processor should be at least Pentium class and a minimum of 8MB RAM is required, 32MB for smother playback
  
• 
  Hard disk should be at least 540MB in capacity
  
• 
  The monitor and video display adapter should conform to SVGA standards and should be able to support 800 X 600 display mode with true color.
  

• 
  To be able to hear sounds, the PC should have a sound card with attached speakers.
  
• 
  Input devices like standards 101 keys keyboard and two button mouse should be present
  
• 
  Multimedia PC system software should be compatible with Windows95 or higher, with standard software for playback of media files in standard formats.
  
• 
  In some cases applications programs like Web browsers, media players and document readers might be required to display additional content.
  

• 
  For production work processors should be at least of the Pentium II class or higher. Memory at least 128MB with 256 recommended.
  
• 
  Multimedia production work require a huge amount of disk space and so typical requirements would around 10GB with 40Gb recommended
  
• 
  Video display adapter should conform to SNGA standards.
  
• 
  CD-ROM drive having a speed of at least 4X but higher speed like 36X
  
• 
  For play back of audio components the PC should have a sound card and attached Speakers.
  
• 
  Editing software are used to manipulate media components to suits the developers requirements. Authoring software are used to integrate all the edited media into a single presentation and built navigational pathways for accessing the media
  

We usually represent analog quantities as “wave” as an analog to the waves on a seashore. Waves can be conceived of energy propagating from one place to another. Apart from electromagnetic radiation which can travel through vacuum other waves require a medium for transport of energy.

The particles of the medium absorb a part of the energy from the source and oscillate or vibrate about their mean position, thereby transferring a part of the energy to the next layer of particle and propagating the wave outwards in all direction from the source.

A wave therefore essentially represents a graph or plot of the motion of a particle or a set of practices in the path of a wave over space or time.

Wave is plots of variation pattern of energy flow.We usually try to arrive at a mathematical model and relation fitting the plot, e.g.: y=Ax²+Bx+C. it is customary however to explain the concepts of a wave by considering a sinusoidal function, i.e.., y=S sin(x) or y= B cos(x).

This is because sinusoids are easier to deal with as they are periodic functions and can be represented by simple equations.

Amplitude A y=A sin (t)

Time t

A Sinusoidal wave

Fundamental Properties of Waves:

Three fundamental properties can be identified in waves that determine the characteristic of the physical quantity that the wave represents.

1. 
   Amplitude
   
2. 
   Frequency
   
3. 
   Waveform
   

The peak amplitude of a wave is the maximum displacement of the oscillating particle from its mean position. Higher amplitude would signify a larger distance between the opposite crests of the wave. The smaller wave B is said to have smaller amplitude than the larger wave.

The amplitude actually represents the intensity of the physical quantity e.g. the brightness of light, the loudness of sound, the voltage current level of electricity etc..,

A

B

The frequency refers to how fast a particle in the path of a wave is oscillating and is defined as the number of oscillations completed by the particle in unit time. Where a higher pitch results in a shrill sound e.g. whistle, while a lower pitch results in a dull and flat sound, e.g. sound of a padded hammer.

A B

Two waves of

Different frequencies

Frequency is measured in a unit called Hertz represented as Hz. A wave is said to have a frequency of 100 Hz when it completes 100 complete oscillations (or complete cycles) in one second.

It represents essentially represents the shape of the wave and signifies the change of the amplitude and frequency over time. A wave can also have an irregular shape without any apparent periodicity. The waveform determines the quality of the physical quantity.

Sinusoidal waves are regarded as elementary waves. Two or more sinusoidal waves can combined together to generate a composite wave which may have a non-sinusoidal shape. The actual shape of the composite wave depends on relative amplitudes and frequencies of the component waves. The composite shape depends on the relative position of the component waves.

Amplitude y

Time t

Sinusoidal waves are not mathematical abstraction; they can be produced in the real world by a phenomenon called Simple Harmonic Motion (SHM). An SHM is a specific type of oscillation exhibited by the spring loaded weight.

A spring loaded weight W is attached to the point P with flexible string T. As P moves along the circle in the anti-clockwise direction, the weight W attached to P oscillates up and down in synchronism. If ω is the angular frequency of the point P in radian/sec, then the frequency of the generated wave is given by

ƒ = ω/2π

Temporal waves depict the state of a single particle in the path of a wave over a period of time. Two points A and A’ or B and B’ depict instances when the particle is in the same state of oscillation, also known as Phase, and the time difference between them is known as the time period T of the wave. Spatial waves on the other hand depict the sate of several particles in the path of a wave at a single instant of time.

Two particle C and C’ or D and D’ are said to be in the same state of the oscillation or same phase and the distance between them is referred as Wavelength λ of the wave, measured in m or μm. The portion of a wave in between two points in the same phase is referred as to as one complete cycle of the wave.

Amplitude y Amplitude y

B B’ D D’

Time t Distance x

A A’ C C’

Speed and Periodicity:

The speed of transmission of wave is the distance travelled by it in unit time, as the wave is propagated from the source to the distance. Distance traveled per unit time can be expressed as the number of cycles crossing a point in the unit time. Number of cycle/sec is the frequency ƒ of the wave and the length of one cycle is the wave length λ. So the velocity ν of the wave in m/sec is given by, ν=λƒ

A wave is said to be periodic if it repeats its wave form pattern periodically, otherwise it is said to be a periodic.

Amplitude y

Time t

Time Period T

Time t

1. 
   A periodic wave (b) An periodic wave
   

Digital quantities are not continuous over space or time, and as such they cannot be represented by smooth waves. They are discrete in nature which means that they exist or have values only at certain points in space or instant in time, but not at other points or instants. It is represented in two numbers as 1 and 0. When it is in 1 then it is in ON position and 0 when it in off position.

Signal amplitude

Space or time

t1 t2 t3 tn

(A discrete set of points)

A real world photograph can be seen because light reflected from it falls on our eyes. We recognize the shade and color in the image because of the various intensity and frequency of the light waves coming to our eyes from the images. The light patterns causing recognition of the image are analog signals.

Converting an analog quantity to a digital form is called sampling. Sampling involves breaking the continuous wave into a discrete set of points. The dashed vertical line represents the point in space or time, where the values of the analog wave are sampled or examined, and the small circles represent the actual values of the wave at those points.

Signal amplitude

Sample points Space or time

Sampling is done at specific intervals of time and is said to be create time-discretization of the signal. For time-independent quantities like a static image, sampling is done at regular space intervals and is said to create space-discretization.

Signal amplitude

Space or time

Sampling Rate:

The rate or frequency at which the sampling occurs is known as Sampling rate or Sampling Frequency.

The output of the sampling step is a set of sample values, which represents the changing analog signal.

Quantization levels refer to the number of different sample values that can be used to represent a digital quantity. The sample values actually represent the amplitudes of the analog wave at different time instant, the process of selecting a fewer number of amplitude levels from a larger set is known as amplitude-discretization.

We have to set a sample values quantized to a specific number of levels, occurring at specific instants of time. Code word generation involves expressing these amplitude levels in terms of binary codes or numbers, because that is finally how the data would be represented within a computer.

To represent the quantized amplitude levels as binary numbers. we follow the well-known rule that starting with n numbers of bits it is possible to generate a total of 2n binary numbers and their values range from 0 to 2^n-1. Here n is known as Bit Depth.

Signal amplitude

11

10

00 Space or time

t1 t2 t3 t4 t5 t6 t7 t8 t9

Physical Storage:

The final stage is to write this information on a storage medium like a hard disk or a compact disc. The binary values are used to generate a voltage pulse with two voltage levels corresponding to 1 and 0 via the read write head. The voltage pulse used in magnetic small area of the magnetic coating on the disk in two different ways to write the corresponding bit. Read write head can sense the difference in the coding of the dipoles and retrieve the stream as 1s and 0s which represent the original quantity.

When converting an analog signal into digital form, the sampling frequency must be greater than twice the bandwidth of the input signal in order to be able to reconstruct the original signal accurately from the sampled version. The low frequency distortion produced due to the lowest sampling rate known as under-sampling is referred as aliasing because the input wave is not truly represented at the output. The sampling frequency that is half that of the input wave frequency is referred to a Nyquist Frequency. When sampling done at much higher rates than that prescribed by the theorem it is called over sampling.

The conversion of an analog signal into digital form is done using an electronic circuit called an encoder. The encoder consists of the actual Analog to Digital Converter (ADC) where the three stage of sampling, quantization and code –word generation is executed. The ADC us preceded by an anti-aliasing filter to remove high frequency components from the input signal thereby possible distortion.

Analog input after removal of high

Frequency components

ADC (sampling, quantization and code word generation)

Anti aliasing filter

Analog Digital

Input Output

Digital conversion is required for storing data inside a computer but when that information is to be perceived by us a s light or sound, it needs to be converted back to analog form. This implemented by passing the digital output through a device called as signal decoder. It consists of the digital to analog convertor DAC followed by a low-pass filter. The binary codes fed to the DAC generate a digital pulse, the amplitude of each level being determined by the code word.

The DAC generates a corresponding analog waveform which approximates the staircase patterns of the digital wave by smooth curves. Normally the high frequency cut off of the low pass filter is made the same as that used in the band limiting filter of the encoder.

Staircase Waveform

Low pass Filter

DAC

Codeword Filter

Decoder

(Decoder: Digital to analog conversion)

Hence, ADC and DAC are often combined into a single unit is called an Encoder-Decoder or ADC –DAC set.

Decoder

Encoder

From scanner or binary data binary data

Microphone

1100010….. 1100010….

(Storage devices, e.g. Analog output to monitor or

Hard disks) Loudspeakers

Text is a set of characters or set of words that form a Text.

It consists of fixed size characters having essentially the same type of appearance. Character set called ASCLL codes are used in this type of text. Each character is represented by 7 bit binary codes. Characters include A-Z, 0 to 9, ( ), &,’; “ “ , +, -, / , *. And it includes control characters such as backspace, Line feed, Space bar, escape etc.., Extended ASCLL code can also be used which is an 8 bit representation.

The control characters are used to change the appearance of the characters, the appearance can be like Bold, Italic, underline. This formatted text is extensively used in publishing sectors for preparation of paper, book, magazine and journals.

Tables and graphs can be inserted to print the formatted text the printer should be capable of interpreting this controls.

Hypertext:

It serves to link different electronic documents and enables the user to jump from one point to another in a non-linear way. It provides method of transmitting information. The text represented is in a sequential form. Technical documents consist of a collection of relatively independent information units. It is used to link multiple documents so that the user can navigate non-sequentially from one document to the other it is called as Hyperlink.

On the web target documents are specified by specific nomenclature called Web site address technically know as URL (Uniform Resources Locators).

UNICODE STANDARDS:

Unicode standards are a new universal character coding scheme for writing characters and text. It defines the consistent way of encoding Multi-lingual text. The capacity of encoding is more than 1 million characters. It deals with only characters and glyphs.

The first bytes in a Unicode represent the language area and the next represent tha actual character.

E.g.: (00) Code for Latin, (0B) is for Greek, (0f) for Tibetan, The mapping methods are called Unicode Transformation Formats (UTF) and Universal character set (UCS).