computer science - data representation

a type of analog signal that is captured and converted into digital form to be processed by a computer

by sampling. (taking measurements of the sound wave at regular intervals and converting these measurements into binary)

the number of bits per sample, determines the level of detail of each sample

MIDI and MP3

Musical Instrument Digital Interface (file)
Stores a set of instructions (for how the sound should be played)
It does not store the actual sounds
Data in the file has been recorded using digital instruments
Specifies everything important so
Individual notes can be edited

MP3 is a format for digital audio
MP3 is an actual recording of the sound
MP3 is a (lossy) compression format
It is recorded using a microphone

using a bitmap (series of pixels)

small dots of colour that are arranged in a grid. each pixel can be represented by a binary code

when the resolution and colour depth increase

2^10 bytes
2^20
2^30
2^40
2^50
2^60

-reduces size without permanently removing data
-repeated patterns are identifies and indexed
- run-length encoding (RLE) and huffman encoding is used
-RLE replaces sequences of repeated characters with a code that represents the character and the number of times it is repeated
-huffman encoding replaces frequent characters with shorter codes and less frequent characters with longer codes

a collection of characters that can be represented in binary

using a character set - a collection of characters and the corresponding binary codes to represent them

ASCII
which assigns a unique 7-but binary code to each character

limit in terms of the number of characters it can represent and doesnt support non-western languages

unicode was developed, which can represent a larger variety of characters (uses 8 or 16 bits)

uses a variable - length encoding scheme that assigns a unique code to each character, which is represented in binary using several bytes

requires more bits per character than ASCII, it can result in larger file sizes and slower processing times when working with text-based data

on the sample rate (number of samples taken per second) the higher the rate the higher the quality, however also increases file size

44.1 kHz and 16-bit binary

the number of pixels in the image, higher resolution = more pixels = more detailed but more storage space

2^8 so 256 different colours

the number of bits used to represent each colour. the higher the colour depth = more colours = more storage

600 x 400 = 240000

1 bit (either 0 or 1)

4 bits

8 bits

resolution (width x height) x colour depth (number of pixels)
(if question is in bytes, divide number of bits by 8)

resolution = 100 x 80 = 800
colour depth = 2^7 = 128 so 7
size = 800 x 7 = 56000bits
bytes = 7000

Sample rate (hz) x sample resolution (bits) x length of sample (seconds)

bits per second = 48000 x 24
size = 1152000 x 30 = 34560000
bytes = 4320000
kibibytes = 4218. 75 (divide 1024)
mebibytes = 4.12 (divide 1024)

lossless and lossy

to reduce the size of large files for storage, transmission and faster processing

for text, code and archival purposes as loosing data would be a problem

-reduces file size permanently
-used to images and audio, where minor details can be removed without impacting the quality
-uses downscaling, reducing resolution or colour depth and reducing samples or rate
-amount of data removed depends on the level of compression selected and can impact the quality of the final file

for media files like audio or images where minor data loss is accpetable