Representing Data

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

1. Audio is captured via an input device e.g microphone

2. The sound travels as an electrical signal

3. Computer/ converter changes this signal into binary data

4. 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