ComputingIntermediate 2

Multimedia Technology

The Development Process and Multimedia Applications

The Software Development Process and Multimedia Applications

• Analysis: The main purpose of this stage is to be absolutely clear about what the multimedia project is supposed to do.

The Development Process and Multimedia Applications

• Design: Producing a detailed plan which defines what the different parts of the project are and how they are linked together.

The Development Process and Multimedia ApplicationsThe Software Development Process and

Multimedia Applications

• Implementation: This is the point at which the multimedia authoring, or web-page authoring, package is used to turn the design into a working project.

The Development Process and Multimedia Applications

The Software Development Process and Multimedia Applications

• Testing: A series of practical tests are carried out to check that the multimedia project functions properly.

• Documentation: User Guide and Technical Guide.

The Development Process and Multimedia Applications

The Software Development Process and Multimedia Applications

• Evaluation: Checks that the finished application meets the user’s requirements. Includes an assessment of the HCI design.

• Maintenance: Fixing bugs and adapting the design to suit client needs and the demands of new technology.

Methodologies used in creation of multimedia applications

• Text editor: Creating simple web pages using HTML.

• WYSIWIG editors: Previewing applications under development to check that what you see is what you get.

• Multimedia authoring packages, e.g. Mediator Pro.

• Presentation software, e.g. PowerPoint.

Methodologies used to view multimedia applications

• Displaying multimedia applications in a browser.

• Displaying multimedia applications using a file player or viewer.

Methodologies used to view multimedia applications

Multimedia application as an executable file

Bit-mapped Graphic Data• Capturing still images

using a digital camera • Using a CCD to capture

light coming in through a lens

• CCD charged coupled device: uses sensors to capture light

• Capturing images using a scanner: also uses CCD

Bit-mapped Graphic Data

• Storing graphics as a bit map: each pixel in the image is represented by a binary number.

• Uncompressed bit-map format: a file which holds a binary number for each pixel in an image.

• Large file size: main limitation of bit-map format.• Need for compression: to relieve demands on

storage and transmission times.

Bit-mapped Graphic Data

Compression using GIF format• Lossless compression: GIF format compresses

graphic data without losing any information about the image. It compresses by encoding repeated patterns of data.

• Limited number of colours: limited to 28, 256 colours.

• Transparency: colours set as transparent let the background colours and patterns show through.

• Used for storing cartoons, and line drawings.

Bit-mapped Graphic Data

JPEG• Uses lossy compression: parts of the

graphic are cut out, e.g. shades of colour. At low rates of compression this is not noticeable.

Bit-mapped Graphic Data

JPEG• JPEG format suitable

for storing photographs

and paintings.

Bit-mapped Graphic Data

Trading quality for file size• Resolution: increasing resolution increases the

number of pixels, can improve the quality of a graphic but increases the file size.

• Colour depth: increasing colour depth increases the number of colours or shades of grey, can improve the quality of a graphic but increases the file size.

• Lossy compression: reduces file size and, providing the rate of compression is not too high, does not affect the quality of the graphic.

Bit-mapped Graphic Data

Simple bit-map editing and creation software

Painting programsFill tool: a feature for pouring colour into a graphic.Paintbrush tool: for more precise application of colour.

Bit-mapped Graphic Data

Main features of image editing programs • Decrease resolution• Alter colour depth• Crop• Alter brightness and contrast• Insert graphic• Re-size.

Bit-mapped Graphic Data

Hardware for displaying 2D graphics

• CRT monitor: bulky, heavy, run on mains power, cost less than equivalent TFT screens.

• LCD and TFT screens: flat, light, need less power, more expensive than CRT.

Bit-mapped Graphic Data

Hardware for displaying graphic data• Need for graphics cards to store and process

graphic data, relieving the main processor of the task.

Digitised Sound DataHardware for capturing sound

• Microphone

• Sound cards: to sample, store and process audio data.

Digitised Sound DataUncompressed sound data

• RAW: Uncompressed samples of sound waves

0101010101010101 1111111101010101 0011001100101011 1100101000110001

• RIFF: Resource Interchange File Format• WAV: Microsoft's format for sound files,

part of RIFF

Digitised Sound Data

• Lossy compression: reduces file sizes by cutting out some of the data.

• MP3: uses lossy compression without noticeable loss of sound quality.

Digitised Sound Data

Balancing file size and sound quality• Sampling depth: increased sound depth =

greater range of values = better sound quality and greater file size.

• Sampling frequency: The higher the sampling frequency, the better the sound quality, the greater the file size.

• Sound time: affects file size but not quality.

Digitised Sound Data

Simple sound editing software• Reducing sample frequency, e.g. from 44.1

KHz to 22.05 KHz, reduces file size and audio quality.

• Reducing sample depth, e.g. from 16 bits to 8 bits per sample, reduces file size and audio quality.

Digitised Sound Data

Editing sound file features:VolumeEffectsEchoReverse

Digitised Sound Data

Sound cards and playback:Sound cards needed to change the digital

audio data into analogue signals to control output from speakers.

Video Data

Hardware for capturing images• Digital video camera

• Web cam

Video Data

Storing video data• Uncompressed format• Uncompressed video data = Large file sizes• 1 second of uncompressed wide-screen

video can take up 53 Megabytes of storage• AVI: Audio Visual Interleave, an

uncompressed format.

Video Data

Compressing video data• MPEG-2Lossy compression: cuts out unnecessary

parts of a video clip

Video Data

Compressing video dataUsing MP3 compression:

• Reduces file sizes

• With no noticeable loss of video quality.

Video Data

Video quality and file size• Colour depth: increasing colour depth improves

quality and file sizes.• Resolution: increasing resolution improves quality

and increases file sizes.• Frame rate: measured in frames per second, fps.

30fps is the rate for a video clip. Increasing frame rate increases file size. Lower frame rates reduce file size but make video clip ‘jerky’.

Video Data

Video quality and file size• Video time: increasing or reducing the time of a

video is the obvious way to affect the file size. Quality of the display of the clip is not affected.

• Lossy compression: Using MP3 compression reduces file sizes without affecting quality.

Video Data

Video editing software features and applications used with single video clips

• Cropping: cutting unwanted data from the beginning and end of a clip.

• Add effects, titles, sound tracks.• The need for graphics cards to process and

output video data.

Vector Graphics Data

Basic features of vector graphics• They are scalable: resolution independent.• In a vector graphic individual objects can be

edited.• Graphics can be assembled by placing

objects in layers.

Vector Graphics Data

Common attributes of vector graphic objects

Position Shape Size

Vector Graphics Data

Common attributes of vector graphic objects Rotation Line Layer Fill

Vector Graphics Data

Attributes of a 3D imageShapePositionSizeRotationTexture

Vector Graphics Data

Standard formats for vector graphicsScalable Vector Graphics (SVG) formatScalable: resolution independentVector: represents objects by defining a series of attributes

Vector Graphics Data

Standard formats for vector graphicsVirtual Reality Markup LanguageA standard language used to model and

animate geometric shapes Used to define 3D environments for the

WWW.

Synthesised Sound Data

Musical Instrument Digital Interface: MIDI

Common attributes of notes stored as MIDI data:– Instrument: defines which instrument is playing– Pitch: defines the height of the note– Volume: determines the amplitude– Duration: determines the length of the note.

Synthesised Sound Data

Common attributes of notes stored as MIDI data

Duration: determines the length of the note.Tempo: the speed at which a piece of music is

played.

Implications: Multimedia Technologies

Converging contemporary technologies• Smartphone: merging technologies of a

mobile phone and a laptop.• Pocket PC: merging technologies of a

laptop, mobile phone and desktop operating system and application software.

Implications of Multimedia Technologies

Contemporary technologies• Digital television: an interactive multimedia

device which, because of the digital nature of its signals, is easily integrated into your digital computer and home networks.

Implications of Multimedia Technologies

Contemporary technologiesVirtual realityThe ultimate multimedia experience where

the user is immersed in the world of the computer and can journey through, and interact with, a computer generated 3-dimensional multimedia world.

Implications of Multimedia Technologies

• Immersive VR • Output :Using speakers, stereo screens,

headsets• Input: sensors in gloves, headsets and suits