Multimedia

A page of a printed book can only carry text and pictures. A computer can carry text, pictures, recorded sound, moving video and animation at the same time, and it can let you choose what to look at next. That combination is what we call multimedia, and it is the reason a computer can teach, entertain, advertise and diagnose in ways that no earlier medium could.

7.1 Introduction to multimedia

The word itself gives the definition away: multi means many and media means the means of communicating. The key words in the definition are integrated (the media work together in one presentation, not side by side), computer controlled and interactive.

A textbook with photographs is not multimedia — it has two media but no computer and no interaction. A film is not multimedia either: it combines pictures and sound, but you cannot change what happens next. A website with text, photographs, a video and buttons that let you choose a topic is multimedia.

Characteristics of multimedia:

• It combines two or more media in one presentation.
• It is digital — every medium is stored as numbers, so all of them can be edited, copied and transmitted by the same machine.
• It is integrated: the media are synchronised, so narration matches the picture on screen.
• It is usually interactive: the user controls the pace and the path through the content.
• It needs large storage and a fast processor, because sound and video carry far more data than text.

A related idea is hypermedia: non-linear multimedia in which the pieces are joined by hyperlinks, so that clicking a word or a picture jumps to related content. The World Wide Web is the largest hypermedia system ever built.

What a multimedia computer needs. On the hardware side: a fast processor, plenty of RAM, a good graphics card (GPU), a sound card with speakers or headphones, a high-resolution monitor, large secondary storage, and capture devices such as a microphone, a scanner, a digital camera and a webcam. On the software side: media players, an image editor, a sound editor, a video editor, an animation tool and an authoring tool that ties them all together.

Advantages	Disadvantages
Uses sight and sound together, so people understand and remember more	Needs expensive hardware and software
Makes abstract ideas visible — a beating heart, a running engine	Files are very large; sharing needs fast internet
The user controls the pace, so learning is self-directed	Producing good content takes skill, time and money
One copy serves any number of students, anywhere	Too much animation and sound distracts from the message
Attracts and holds attention in advertising and teaching	Can encourage passive watching instead of active thinking

7.2 Components of multimedia

The five components are text, graphics, audio, video and animation. Learn them in that order: it is the order the syllabus uses, and it runs from the smallest files to the largest.

Text

Text is the oldest and smallest component — a page of plain text is a few kilobytes. It carries precise meaning that a picture cannot: a name, a date, a price, an instruction. In a multimedia product, text appears as headings, body text, captions, menu labels and buttons.

• A font (typeface) is a complete set of characters in one design — Arial, Times New Roman, Preeti. Its size is measured in points (1 point = 1/72 inch), and its style may be regular, bold, italic or underlined.
• Static text simply sits on the screen; hypertext is text that links to other content when clicked.
• Common formats: .txt (plain text, no formatting), .rtf (rich text), .docx, .pdf, .html.
• Software: Notepad, MS Word, LibreOffice Writer.

Graphics

Graphics are still pictures — photographs, drawings, diagrams, logos, charts. They are the fastest way to show what something looks like. There are two fundamentally different ways a computer can store a picture, and the difference is examined nearly every year.

	Raster	Vector
Made of	pixels	mathematical shapes
On enlarging	blurred, blocky	stays sharp
File size	large, grows with resolution	small, grows with complexity
Best for	photographs, scanned images	logos, icons, maps, technical drawings
Formats	JPEG, PNG, GIF, BMP, TIFF	SVG, AI, EPS, CDR
Software	Adobe Photoshop, GIMP, MS Paint	Adobe Illustrator, CorelDRAW, Inkscape

Three ideas describe any raster image. Resolution is the number of pixels, written as width × height (1920 × 1080). Colour depth (or bit depth) is the number of bits used per pixel: 1 bit gives 2 colours, 8 bits give 256, and 24-bit "true colour" gives 2²⁴ ≈ 16.7 million. Compression shrinks the file, and is either lossy (JPEG — throws away detail the eye is unlikely to miss, so the file is small but quality falls each time it is re-saved) or lossless (PNG, GIF — nothing is discarded and the original can be rebuilt exactly).

Audio

Audio is sound in digital form — narration, music, sound effects, warning beeps. Sound reaches a microphone as a continuous (analogue) wave, and the computer converts it into numbers by sampling: measuring the height of the wave many thousands of times a second and storing each measurement.

• Sampling rate is how many measurements are taken per second, in hertz. CD quality is 44,100 Hz (44.1 kHz).
• Bit depth is how precisely each measurement is stored — 16 bits for CD audio.
• Channels: mono is one channel, stereo is two, surround sound more.

Higher values in any of these give better sound and a bigger file.

• Formats: MP3 (lossy, small, universal), WAV (uncompressed, large, full quality), AAC, OGG, WMA, MIDI (not a recording at all — a list of instructions saying which note to play on which instrument, so the files are tiny).
• Software: Audacity, Adobe Audition, Sound Forge.

Video

Video is a sequence of still images (frames) captured from the real world and played back fast enough to look continuous, almost always with a synchronised sound track. The number of frames shown per second is the frame rate; 24 frames per second is the cinema standard, and 25 or 30 fps is normal for television and the web.

Video is the largest of the five components. One second of uncompressed 1920 × 1080 true-colour video at 30 fps would be about 178 MB, so video is always compressed, by codecs such as H.264 and H.265.

1Playhead — the vertical line marking the frame currently shown in the preview window2V2, an empty second video track; tracks are stacked, and an upper track covers what is beneath it3V1, the video track holding the clips of the film, each clip a separate rectangle that can be trimmed or moved4A1, the matching audio track — the green blocks are the sound waveforms belonging to those clips5A2, a spare audio track, free for background music or a voice-over

• Formats: MP4 (the default choice today), AVI, MKV, MOV, WMV, FLV, WebM.
• Software: Adobe Premiere Pro, Kdenlive, OpenShot, Windows Video Editor.

Animation

Animation works because of persistence of vision: the human eye retains an image for about a sixteenth of a second after it disappears, so images shown faster than about 16 per second blend into continuous motion.

Kinds of animation:

• Cel or frame-by-frame animation — every frame is drawn separately, the traditional cartoon method.
• Tweening (in-betweening) — the artist draws only the first and last frames (the key frames) and the software calculates all the frames between them.
• Path animation — an object is moved along a drawn path.
• Morphing — one image is gradually transformed into another.
• 2D animation works in height and width only; 3D animation builds objects in a three-dimensional space with depth, lighting and camera angles, and is what modern animated films use.

Formats: GIF (short looping animations, 256 colours), SWF (the old Flash format, now obsolete), SVG with CSS or JavaScript, MP4 for rendered 3D work. Software: Adobe Animate, Blender, Synfig Studio, Autodesk Maya.

7.3 Applications of multimedia

Education and training. Computer-assisted learning packages, e-learning websites, virtual laboratories and interactive encyclopedias. A simulated chemistry experiment can be repeated without cost or danger, and a video of a heart beating teaches anatomy better than a still diagram. Flight and driving simulators train pilots and drivers without risking an aircraft.

Entertainment. Computer and mobile games, animated films, streaming services, digital music. This is the industry that has driven most multimedia hardware development, because games demand the fastest graphics processors.

Business and advertising. Multimedia presentations to clients, video conferencing, animated television and web advertisements, product demonstrations and virtual showrooms where a customer can rotate a product on screen.

Public information and kiosks. Touch-screen kiosks at airports, museums, banks and hospitals; digital notice boards; government information portals. Because they are interactive, a visitor finds just the item wanted instead of reading a whole board.

Medicine. Scanned images from MRI and CT machines assembled into three-dimensional views; surgical simulators on which surgeons practise; patient education videos; telemedicine, in which a specialist in Kathmandu examines images and video sent from a district hospital.

Engineering and science. Computer-aided design (CAD) of buildings and machines, three-dimensional walk-throughs of a building before it is built, scientific visualisation of weather and earthquake data.

Journalism and publishing. Online newspapers combining text, photographs, video and interactive graphs; e-books with embedded audio; digital archives.

Arts and entertainment production. Digital photography and photo editing, music production, film special effects and computer-generated imagery (CGI).

Chapter summary

• Multimedia is the computer-controlled, integrated use of more than one medium — text, graphics, audio, video and animation — usually with interactivity.
• Linear multimedia runs in a fixed order with no user control (a film); non-linear multimedia lets the user choose the path (a website, a game). Hypermedia is non-linear multimedia joined by hyperlinks.
• Text is the smallest component and carries exact meaning; fonts are measured in points (1 point = 1/72 inch); formats .txt, .rtf, .docx, .pdf, .html.
• Graphics are still pictures. Raster images are grids of pixels, are resolution dependent and go blocky when enlarged (JPEG, PNG, GIF, BMP); vector images store shapes as mathematics, are resolution independent and stay sharp (SVG, AI, EPS, CDR).
• Image size depends on resolution (pixels), colour depth (24-bit true colour = 16.7 million colours) and compression — lossy (JPEG) discards detail, lossless (PNG, GIF) does not.
• Audio is digitised by sampling: CD quality is 44,100 Hz at 16 bits. MP3 is lossy and small, WAV is uncompressed and large, MIDI stores instructions rather than sound.
• Video is captured frames plus synchronised sound, measured in frames per second (24 fps cinema, 25–30 fps television). A codec compresses it; a container (.mp4, .avi, .mkv) holds the parts together.
• Animation is drawn or computed frames, not captured ones, and works by persistence of vision. Methods: frame-by-frame, tweening between key frames, path animation and morphing; 2D against 3D.
• Applications: education and training, entertainment, business and advertising, public information kiosks, medicine, engineering, journalism and the arts.

Practice questions

Group A — Multiple choice (1 mark each)

1. Which one is not a component of multimedia? [1]aTextbAnimationcCompilerdAudio
2. A cinema film that cannot be controlled by the viewer is an example of [1]alinear multimediabnon-linear multimediachypermediadinteractive media
3. Which type of graphic stays sharp when it is enlarged? [1]abitmapbrastercvectordJPEG
4. The standard sampling rate of CD-quality audio is [1]a8,000 Hzb22,050 Hzc44,100 Hzd96,000 Hz
5. The number of frames displayed per second in a video is called its [1]aresolutionbframe ratecbit depthdsampling rate
6. Which file format uses lossy compression? [1]aPNGbBMPcJPEGdGIF
7. Creating the frames between two key frames automatically is called [1]amorphingbtweeningcrenderingdsampling
8. Animation is possible because of [1]apersistence of visionbrefractioncsamplingdcompression
9. In 24-bit true colour, the number of colours available is about [1]a256b65,536c16.7 milliond4.3 billion

Answers to Group A

1. (c) — a compiler is a translator program, not a medium.

2. (a) — linear multimedia runs start to finish with no user control.

3. (c) — vector images are redrawn from stored shapes.

4. (c) — 44.1 kHz at 16 bits is CD quality.

5. (b) — frames per second.

6. (c) — JPEG discards detail the eye is unlikely to notice.

7. (b) — tweening, short for in-betweening.

8. (a) — the eye holds an image for about 1/16 of a second.

9. (c) — 2²⁴ ≈ 16.7 million.

Group B — Short answer (5 marks each)

1. Define multimedia. Explain any four of its characteristics. [5]
2. Differentiate between linear and non-linear multimedia with two examples of each. [5]
3. Differentiate between raster and vector graphics with any five points. [5]
4. What is animation? Explain any four types of animation. [5]
5. Explain the audio and video components of multimedia, naming three file formats and one piece of software for each. [5]
6. Calculate the uncompressed size, in megabytes, of a 1600 × 1200 image stored in 24-bit colour. Explain why compression is necessary. [5]

Answers to Group B

1. Multimedia is the integrated, computer-controlled use of more than one medium — text, graphics, audio, video and animation — usually with interactivity. Characteristics: it combines two or more media; everything is digital; the media are integrated and synchronised; it is normally interactive, with the user choosing the path and the pace; and it demands large storage and a fast processor.

2. Linear multimedia plays from beginning to end in a fixed order with no user control — examples: a cinema film, an automatically playing slideshow. Non-linear multimedia lets the user choose what to see next through menus, buttons and links — examples: a website, a computer game. Linear content is easier and cheaper to produce; non-linear content holds attention longer and suits self-paced learning.

3. See the comparison table in §7.2: made of pixels against mathematical shapes; blurs when enlarged against stays sharp; large file size against small; suits photographs against suits logos and maps; JPEG/PNG/GIF/BMP against SVG/AI/EPS/CDR; Photoshop or GIMP against Illustrator or Inkscape.

4. Animation is the illusion of movement created by displaying a rapid sequence of still images that differ slightly, the images being drawn or computed rather than captured. Types: frame-by-frame (cel), where every frame is drawn separately; tweening, where only the key frames are drawn and the software fills in the rest; path animation, where an object follows a drawn path; and morphing, where one image is gradually transformed into another.

5. Audio is digitised sound — narration, music and effects — produced by sampling an analogue wave, typically at 44,100 Hz and 16 bits. Formats: MP3 (lossy, small), WAV (uncompressed), MIDI (instructions, not a recording). Software: Audacity. Video is a sequence of frames captured from the real world with synchronised sound, measured in frames per second and always compressed by a codec. Formats: MP4, AVI, MKV. Software: Adobe Premiere Pro (or Kdenlive).

6. 1600 × 1200 = 1,920,000 pixels. At 24 bits = 3 bytes per pixel, that is 5,760,000 bytes, and 5,760,000 ÷ (1024 × 1024) = 5.49 MB. Compression is necessary because uncompressed images and especially video are far too large to store in quantity or send over a network — one second of uncompressed 1080p video at 30 fps is about 178 MB, which no ordinary internet connection could stream.

Group C — Long answer (8 marks each)

1. (a) Define multimedia and explain the five components with one example of each. [5](b) Explain any three hardware requirements and any three software requirements of a multimedia computer. [3]
2. (a) Explain any six applications of multimedia, with one sentence on how multimedia helps in each. [6](b) State any two advantages and any two disadvantages of multimedia. [2]

Answers to Group C

1. (a) The definition is in §7.1. Text — the caption naming a photograph; smallest component, carries exact meaning. Graphics — a photograph of Mount Everest or a vector map of a national park; still pictures, raster or vector. Audio — a recorded narration or a bird call, digitised by sampling. Video — a filmed interview; frames captured from reality with synchronised sound. Animation — a cartoon showing how a river changed course; frames drawn or computed rather than captured.

1. (b) Hardware: a fast processor to decode compressed video in real time; a graphics card (GPU) to render images and 3D scenes; a sound card with speakers, and large secondary storage because media files are huge; capture devices such as a microphone, scanner, webcam or digital camera. Software: an image editor such as GIMP; a sound editor such as Audacity; a video editor such as Kdenlive; media players and an authoring tool to combine everything.

2. (a) Education — simulations and videos make dangerous or invisible processes safe to watch and repeatable. Entertainment — games and animated films are built entirely from multimedia. Business and advertising — animated advertisements and virtual showrooms let a customer examine a product before buying. Public information kiosks — a touch screen at an airport or museum lets each visitor find only the item wanted. Medicine — MRI and CT slices are assembled into 3D views, and surgeons rehearse on simulators. Engineering — CAD models and 3D walk-throughs show a building before it is built. Journalism — online news combines text, photographs, video and interactive graphs in one story.

2. (b) Advantages: it uses sight and sound together, so people understand and remember more; the user controls the pace, which suits self-directed learning. Disadvantages: it needs expensive hardware, software and skill to produce; the files are very large, so sharing them needs fast internet and plenty of storage.