Information representation and multimedia Flashcards
Bit-map images are made up of ________
Pixels
Colour depths
The number of bits used to represent a pixel
Bit depths
It determines the Color depth of that pixel
An increase in bit depth, increases _________
The number of possible colors
Image resolution
The number of pixels that make up an image.
Screen resolution
The number of horizontal & vertical pixels that make up a screen display.
Pixel density
The number of pixels per square inch
How do you calculate the pixel density?
1) add together the squares of the resolution size
2) find the square root
3) divide by the screen size
What are the drawbacks of using high resolution images?
- Increase in file size
- increase in download time
What are 2 things that must be considered when the file size needed to store a bit-map image?
-image resolution
-bit depth
What are vector images?
Images that use mathematical formulas to draw lines and curves that can be combined to create an image
Vector graphics contains a drawing list which are a _______
set of commands used to define a vector image
Vector images tend to be ______ than bitmap images because a bitmap image has to _________ for each individual pixel that forms the image
- smaller
- store color information
A vector image only has to store mathematical formulas that make up the image, which _______
- takes up less space
The 3 most popular image formats used on the web are _________, and are all bitmap formats
- PNG
- JPEG
- GIF
What are vector graphics?
a graphic consisting of components defined by geometric formulae and associated properties, such as line color and style
Sound is an _______ value
analogue
An ______ is used to digitise sound into files
ADC converter
If the sound is going to be used as a sound file, it gets __________
filtered first to remove higher and lower frequencies
_________ is the number of bits used to represent each sample
Sampling resolution
The higher the sample resolution, the better the audio quality.
Because if more bits are available for each sample, ________
then more levels of the signals can be captured, improving the detail of the recording
________ is the number of sound samples taken per second.
The higher the sampling rate and/or sampling resolution, the greater the file size
Sampling rate
How is sampling used to record a sound clip?
1. ________ of the soundwave is _______ at ________
2. (this gives an approx. representation of the sound wave,)
3. Sound wave is then encoded as a series of binary digits
- amplitude
- determined
- set time intervals
how does a microphone digitise sound?
- microphone measures change in air pressure
- microphone translates air pressure into electrical voltage
- ADC digitizes electrical voltage to bytes of info
- computer displays the digitized sound for manipulation
________ is the amount of data that can be transmitted in a fixed amount of time.
- bandwidth
Digital devices express them in bits per second (bps). Analog devices express them in cycles per second (Hz)
What are the factors that affect the digital audio quality?
- sample rate
- sample resolution/bit depth
__________ the number of bits used to store one second of sound
bit rate
File size formula (for sound)
sample rate x sample resolution x sound length
Bit rate formula
frequency x bit depth x channels
file size formula (for screen and pictures)
total pixels x colour depth
coloured images need at least __________ to code them
8 bits or 1 byte for 1 pixel
Monochrome images need _______ to represent the color
1 bit for 1 pixel
A common audio sample rate for music is _________
44,100 samples per second
___________ are the number of frames recorded per second
frame rate
_________ are the smallest picture element which can be drawn
pixels
_______ is a type of compression where all data from the original file can be reconstructed when the file is uncompressed again
lossless
______ is a type of compression where the file compression algorithm gets rid of unnecessary data
Lossy
________ uses audio compression to convert sounds into an MP3 format
MPEG-3 (MP3)
audio compression with an MPEG-3 reduces the file size by __________
90%
____________ allows an original music file to be reduced by 90% while keeping most of the music quality
perpetual music shaping
MP3 files uses a _______ format
lossy
Quality of mp3 files can differ depending on the _______
bit rate
_______ gives a sound quality close to CDs
200 kilobits and higher
__________ format allows the storage of multimedia files rather than sound
MPEG-4 (MP4)
photographic (bit-map) images when compressed, both _________ is reduced
- file size
- image quality
_______ is a common file format for images that uses lossy compression
JPEG
A JPEG reduced the image by a factor between _______, depending on the quality
5 and 15
Run Length Encoding (RLE) is a form of ___________ that reduces the size of _______
- lossless compression
- identical data
A repeated string is encoded into 2 values.
- the first value represent the ______
- the second value represent the ________
- no. of identical data items
- code of the data item (such as ASCII code)
Methods of compressing movie files.
- reduce the ________
- reduce the ____
- reduce the _______
- sampling rate used
- sampling resolution
- frame rate
Methods of compressing image files.
- ______ the image
- _____ the colour/bit depth
- _______ the image resolution
- crop
- decrease
- reduce
