Data Representation - Storing Images and Sound Flashcards
What is the most common type of image?
A bitmap
What are bitmap images?
Images made up of tiny dots called pixels
What colour is 0 in bitmap?
White
What colour is 1 in bitmap?
Black
How many bits represent each pixel in a black and white photo?
1 bit as there are only two colours
How many colours are in 2-bit images?
4 colours
What are the colours and their respective binary values in 2-bit images?
00 = white
01 = light grey
10 = dark grey
11 = black
What is colour depth?
The number of bits used per pixel
How do you work out the total amount of colours with colour depth?
Total amount of colours = 2 to the power of bits per pixel (1-bit image = 2 to the power of 1)
What colour depth do most devices?
24-bit colour depth
What is image size?
The number of pixel in an image (width x height)
What does more pixel mean for the image?
The image will have a higher quality
How do you work out file size in bits?
Image size (length x width) x colour depth
How is sound recorded by a microphone?
As an analogue signal
What are analogue signals?
Pieces of continually changing data
What does an analogue to digital converter do?
Converts analogue signals into digital data that computers can read and store
What is sampling?
The process of converting an analogue signal to digital data
How do you convert analogue recording to digital data?
Sample the amplitude of the wave at regular intervals - amplitude can only take values depending on the sample resolution
Why is digital data different to an analogue wave?
Digital data isn’t continuous so it loses a lot of data
What is the sample rate?
The amount of samples taken per second
What is sample rate measured in?
Hertz (Hz)
How many Hertz are in 1 kilohertz?
1000 Hertz
What is sample resolution?
The number of bits available for each sample
What is the bit rate?
Sample rate (Hz) x sample resolution (bits)
What is the formula for file size?
Sample rate (Hz) x sample resolution (bits) x length (seconds)
What will increasing the sample rate do?
The sound will be of better quality and will more closely match the original recording
What would increasing the sample resolution do?
Make the sampled sound closer to the quality of the original recording by PICKING UP QUIETER SOUNDS
What is the disadvantages of increasing the sample rate and sample resolution?
It will increase the file size
