3.3 Fundamentals Of Data Representation Flashcards
What is a bitmap image?
Image of grid of pixels, that’s a picture element, smallest area or bitmap graphic
Each pixel represented by bit pattern (colour)
Image size = WxH of pixels
File size = colour depth x image size
Affecting factors of file size
More colours more colour depth more storage
More pixels higher resolution more storage
Finding colour depth
Eg 20 colours
20-1 =19
19 in binary = 1111
= 4 bits to represent
Storing analogue sounds
microphone
Transducer converts analogue sound into electrical signals
Then converted to digital binary values (=sampling)
File size of sound
In bits
Sampling rate per second x sample resolution x seconds
Data compression define
Why?
Modify data to Reducing file size
Less storage capacity, Less time to transfer, less network bandwidth consumption
Two kinds of compression
Lossy and lossless
Lossy is irreversible and data is lost
Example of lossless compression
Run length encoding eg (4 1), (2 0) 111100
Huffman coding those tree graphs + freq table
why is ASCII limited?
ASCII only has 7 bits so can only code for latin alphabet, 128 characters , so other alphabets are not represented for
why is unicode more accessible
unicode codes for 8 or 16 bits, so maximum can code for 65536 characters, more universal to represent for other alphabets beyond latin
how is analogue sound recorded
microphone picks up sound waves
converted to an electrical analogue signal
value read and rounded
binary representation stored
why a sound recordin with high sample rate normally result in better quality recording
more measurements taken
= less missing parts of original sound
= more accurate
stages in converting sound to a digital form
- microphone picks up sound waves, sampling rates at regular intervals
- converted to electrical analogue signal
- value read at specific point and rounded to a level
- binary values stored
define sample resolution
number of bits to represent a sound sample
define sampling rate
number of samples taken per second
