Chapter 1: Information Representation

Question 1

What is a pixel

Answer 1

Smallest picture element which can be drawn

Question 2

What is screen resolution

Answer 2

The number of pixels which can be viewed horizontally and vertically on the screen //
or by example - A typical screen resolution is 1680 pixels × 1080 pixels.

Question 3

What is the sampling rate

Answer 3

The number of samples taken per unit time // the number of times the amplitude is
measured per unit time

Question 4

What is the sampling resolution

Answer 4

The number of distinct values available to encode/represent each
sample

Specified by the number of bits used to encode the data for one
sample

Sometimes referred to as bit depth

Question 5

What is the image resolution

Answer 5

The number of pixels per unit measurement

Question 6

How does the sampling rate influence the accuracy of a digitised sound

Answer 6

Increasing the sampling rate will increase the accuracy / precision of the digitised
sound // Increasing the sampling rate will result in smaller quantisation errors

Question 7

How does the sampling resolution influence the accuracy of a digitised sound

Answer 7

A larger sampling resolution will mean there are more values available to
store each sample

A larger sampling resolution will improve the accuracy of the digitised sound
// A larger sampling resolution will decrease the distortion of the sound

Increased sampling resolution means a smaller quantisation error

Question 8

What is meant by run length encoding

Answer 8

Lossless method of compression.

Reduces (the physical size of) a string of adjacent, identical characters/pixels / bytes
etc..

The repeating string (a run) is encoded into two values.

One value represents the number of (identical) characters in the run (the run count).

The other value is the code of the character / colour code of pixel etc. in the run (the run value).

The run value and run count combination may be preceded by a control character.

Any valid example given.

Question 8

What data items are stored in a file header of a bit mapped image

Answer 8

Confirmation that the file is a BMP

File size

Location/offset of image data within the file

Dimensions of the image (in pixels) // image resolution

Colour depth (bits per pixel, 1, 4, 8, 16, 24 or 32)

Type of compression used, if any

Question 8

How is sampling used to record sound clips

Answer 8

The height/amplitude of the (sound) wave is determined.

At set (time) intervals // by example of sensible time period.

To get an approximation of the sound wave

And encoded as a sequence of binary numbers // and converted to a digital signal.

Increasing the sampling rate will improve the accuracy of the recording

Question 9

What features are found in software fore editing sound files

Answer 9

frequency, amplitude, pitch alteration

fade in/out of a clip

mix/merge multiple sound sources/tracks

Question 9

What are differences between bitmap and vector graphics.

Answer 9

Bitmap is made up of pixels
// Vector graphic store a set of instructions about how to draw the shape

Bitmap files are usually bigger than vector graphics files // Take up more memory space

Enlarging a bitmap can mean the image is pixelated
// vector graphic can be enlarged without the image becoming pixelated

Bitmap images can be compressed (with significant reduction in file size)
// Vector graphic images do not compress well

Bitmaps are suitable for photographs / scanned images
// Vector graphics are suitable for more geometric shapes

Bitmap graphics use less processing power than vector graphics

Individual elements of a bitmap cannot be grouped
// Individual elements of a vector graphic can be grouped

Vector graphics need to be ‘rasterised’ in order to display or print