Unit 13 Flashcards
Digital Video
A sequence of digital still images displayed in rapid succession in order to simulate different types of animations and effects
Frame
Each image in a video
pixels
The small elements in which a digital image is made up of, each of which is associated with a color and an intensity
Resolution
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.
The relationship between resolution, pixels, and storage:
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.
What are two ways to reduce the amount of memory required?
1) Reduce the number of pixels required, therefore reducing image resolution
2) compress the data using compression software
List the basic parameters that affect which playback hardware can be used to play a video
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
Script
a collection of instructions and statements that are interpreted, one by one, by the program in order to perform some task
Advantage of using a script:
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
A Function
a specific command to create or manipulate a video
An argument
any variable input within the function
An argument can be:
- a text string
- an integer (whole number)
- a boolean value (true or false)
- name of a file
- a decimal number
List AvsP’s three major areas
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)
Syntax
very specific structure that scripting languages use
Advantages of naming variables/functions:
1) Increased readability of the scripts
2) To use the arguments in arbitrary order
A color model
a system for creating a range of colors from a set of primary colors.
Two popular color models
1) RGB - Red, Green, Blue
2) CMY - Cyan, Magenta, Yellow
RBG or RGB24
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)
RGB32
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
CMY
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)
ImageReader
the function that enables AviSynth to display an image and it much have at least one argument that indicates where the image is located
The main editing functions:
cut
crop
pan
resize
layering effect
zoom-in
zoom-out
Why is it not preferred to reduce frame rate as a form of compression?
Because it can make any effects in the video such as zoom-in or zoom-out appear jerky
Anti-aliasing
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
