Unit 13

Question 1

Digital Video

Answer 1

A sequence of digital still images displayed in rapid succession in order to simulate different types of animations and effects

Question 2

Frame

Answer 2

Each image in a video

Question 3

pixels

Answer 3

The small elements in which a digital image is made up of, each of which is associated with a color and an intensity

Question 4

Resolution

Answer 4

Is a measure of the amount of detail a digital image can hold, and is dependent on the number of pixels used to make that image.

Question 5

The relationship between resolution, pixels, and storage:

Answer 5

The more pixels there are per unit area of the image the higher is its resolution, but the greater the storage requirement in terms of memory space.

Question 6

What are two ways to reduce the amount of memory required?

Answer 6

1) Reduce the number of pixels required, therefore reducing image resolution
2) compress the data using compression software

Question 7

List the basic parameters that affect which playback hardware can be used to play a video

Answer 7

1) The size of the frame (the number of pixels across and down)
2) Frame rate (number of frames displayed per second)
3)The way the color in each pixel is represented
4)The way the video is compressed

Question 8

Script

Answer 8

a collection of instructions and statements that are interpreted, one by one, by the program in order to perform some task

Question 9

Advantage of using a script:

Answer 9

1) once written, the script can be reused to perform the same task at some later time
2) scripts can be edited to achieve a slightly different result if the user wants, without having to start from scratch

Question 10

A Function

Answer 10

a specific command to create or manipulate a video

Question 11

An argument

Answer 11

any variable input within the function

Question 12

An argument can be:

Answer 12

• a text string
• an integer (whole number)
• a boolean value (true or false)
• name of a file
• a decimal number

Question 13

List AvsP’s three major areas

Answer 13

1) Upper area for displaying and editing the script
2) Lower area that has two parts:
- left part used to show a preview of a frame of the video produced by the interpreted script
- right part used to show the functions mentioned in the script, with their arguments
3)

Question 14

Syntax

Answer 14

very specific structure that scripting languages use

Question 15

Advantages of naming variables/functions:

Answer 15

1) Increased readability of the scripts
2) To use the arguments in arbitrary order

Question 16

A color model

Answer 16

a system for creating a range of colors from a set of primary colors.

Question 17

Two popular color models

Answer 17

1) RGB - Red, Green, Blue
2) CMY - Cyan, Magenta, Yellow

Question 18

RBG or RGB24

Answer 18

a color model that uses the primary colors red, green, and blue.
Computers usually use 24 bits to specify colors using RGB color model
Eight bits are allocated to the red, eight to the green, and eight to the blue channel
The intensity of each of these primary colors can be represented as a whole number, and the use of eight bits for each means that the intensity is represented on a scale from 0 to 255
The result is a total of 16777216 possible colors (cause 256 reds * 256 greens * 256 blues)

Question 19

RGB32

Answer 19

a different color model that provides an additional eight-bit channel, known as the alpha channel, that can add different degrees of transparency to an image or a video to be displayed

Question 20

CMY

Answer 20

a color model that uses the primary colors cyan, magenta, and yellow
The primary colors are presented by percentages (0 to 100% for each color)

Question 21

ImageReader

Answer 21

the function that enables AviSynth to display an image and it much have at least one argument that indicates where the image is located

Question 22

The main editing functions:

Answer 22

cut
crop
pan
resize
layering effect
zoom-in
zoom-out

Question 23

Why is it not preferred to reduce frame rate as a form of compression?

Answer 23

Because it can make any effects in the video such as zoom-in or zoom-out appear jerky

Question 24

Anti-aliasing

Answer 24

aims to remove or reduce the jagged appearance by blurring the colors (or tones in a black and white image) so that the effect of the sharp-edged pixels is softened into the surrounding pixels

Question 25

Lossless compression

Answer 25

no data is lost during the compression process
most effective where there are frequently recurring data sequences in the image

Question 26

GIF (Graphics Interchange Format) standard

Answer 26

an example of lossless image compression
can achieve lossless compression ratios of ten on appropriate types of images

Question 27

Lossy compression

Answer 27

reduces file size by discarding redundant data so that only a part of the original data is retained after compression

Question 28

What makes an effective compression program?

Answer 28

The trick in developing successful compression programs is to make sensible decisions about what kind of degradation can be allowed to occur, so that the recovered version is indistinguishable from the original to human senses

Question 29

Block-based techniques in lossy compression

Answer 29

• most frequently used lossy compression technique
• It is the basis of the main current compression standards JPEG and MPEG
• benefit: visible effects on the image can be negligible

Question 30

JPEG

Answer 30

Joint Photographic Experts Group

Question 31

MPEG

Answer 31

Moving Picture Experts Group

Question 32

Explain how block-based technique works in lossy compression:

Answer 32

• Starts by dividing the image into small blocks of pixels, typically square arrays of 8x8 pixels.
• Each 64 pixels in any blocks has a certain color value and hence, assuming a basic 256 color code, a complete description of the colors will take up to 64 bytes
• The compression technique works by finding a reasonably accurate, but concise, description of this combination of 64 color values that takes up less than 64 bytes of storage space. Each block is treated this way
• The complete image is the represented by a set of these concise but not quite precise block descriptions and the original pixel values are discarded.