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What is the sample rate?
Number of audio samples captured per second measured in hertz
How does sample rate affect file sizes?
More samples = more accurate reproduction = better quality = larger file sizes
What is the bit depth?
Number of bits available for each sample, the higher the greater the accuracy and quality
What is the bit rate?
data/bits processed in a given time (kbps), the higher the more realistic
What is an analogue signal?
continuous varying signal to represent sound waves
What is analogue to digital conversion?
Converting analogue signal into digital format for a computer to store
Why do we need ADC?
Humans hear in analogue, whereas computers work in digital so they need to convert
Steps for ADC
Audio is captured via an input device e.g microphone
The sound travels as an electrical signal
Computer/ converter changes this signal into binary data
Software saves data as sound files with quality being determined by sample rate, bit depth and bit rate.
What are the units for frequency?
Hertz
What is data?
raw facts and figures with no meaning
What is information?
processed data with meaning
How is data processed?
using an information system
Bit
smallest unit of digital data represented by a 1 or 0
Nibble
4 bits
Byte (B)
8 bits, used to represent 1 character
Kilobyte (Kb)
1024 bytes
Megabyte (Mb)
1024 kilobytes
Gigabyte (Gb)
1024 megabytes
Terabyte (Tb)
1024 gigabytes
What are the multiples of bytes used for? (b, kb, mb, gb, tb)
to describe memory capacity
In real life, data is stored in..
analogue format
In computers, data is stored in…
digital format
Numeric (integer)
positive or negative whole numbers
Numeric (real)
positive or negative numbers, including decimal/ fractional parts
Data/time
represents date and time in multiple formats
long date: DAY MONTH YEAR
medium date: DD-MMM-YYYY
short date: DD/MM/YYYY
long time: HH:MM:SS
medium time: HH:MM AM/PM
short time: HH:MM
Character
A single letter or digit represented by codes from character set
What is ASCII
character set with each character represented uniquely by a single byte
String
Textual data in the form of a sequence of characters
What is a pixel?
Smallest unit of an image displayed with its own colour
What is resolution?
the quality of an image, determined by the number of pixels
Effect of resolution on file size
Higher the resolution, the greater the number of pixels, and therefore too the file size
Typical bits per pixel (JPEG)
24 bits
How are bitmap graphics stored?
Stored as a grid of pixels, each with a specific color and can be compressed
How are vector based graphics stored
mathematical instructions to create shapes and lines
Difference between bitmap and vector based graphics
Bitmap loses quality when resized while vector scales
Formats for bitmap graphics
.bmp
.dib
jpeg
gif
tiff
.png
Formats for vector based graphics
.svg
.cgm
.odg
.eps
.xml
What is streaming?
allows a video to be viewed on a website without downloading or a time delay
How does streaming work?
downloading in ‘real time’ to prevent waiting
What is a buffer?
Temporary memory used to download the next part of a video before watching it
What does bufferring do?
prevents possible interruptions if there are time delays in streaming
