Images And Sound Flashcards
(26 cards)
How is an image displayed on a screen?
In the form of dots called pixels
What is colour depth?
the number of bits used to represent the color of a pixel in an image
How many unique colours can be created with 24 bits?
16.7 million
What is resolution?
The number of pixels per unit of measurement
How are bitmap images stored?
They are stored in computer memory as a grid of pixels, each pixel stored as a specific colour.
What are two examples of bitmap images and what are they used for?
JPG- Used to store photographs by digital cameras and taking pictures of real world scenes.
GIF-Used to store images such as logos or animations where colours are limited.
What are vector images and name some examples of properties.
Shapes/objects stored using specific properties of a shape. Eg. Length,line colour,fill colour
What are advantages of vector images?
-Doesn’t deteriorate when enlarged
-Faster to transmit
-Faster to load
-Uses less memory
-Easier to manipulate objects in an image
What is the difference between analogue and digital sound?
Analogue is continuous whereas digital is discrete(in binary form)
What is a ADC?
Anologue to digital converter.
What is a DAC?
Digital to analogue converter.
What is a PCM?
Pulse code modulation, a process for coding sampled analogue signals by recording height of each sample in binary equivalent.
How does an ADC work?
1)Samples taken at regular fixed intervals of time. These samples measure amplitude of the signal(height) of the sample at this time known as pulse amplitude modulation.
2)PAM samples are quantised as height of each PAM pulse is approximated by n bit integer.
3) Height of each PCM pulse is encoded in bits to produce digital output in binary form. Output of PCM encoder is sequence of integer numbers.
What two factors determine the quality and accuracy of sound produced?
Sampling rate and Resolution
What is the definition of samples?
Measuring value of analogue signals at regular intervals.
What is the sampling rate of CD quality sound?
44khz
What is Nyquists rate?
For lossless digitization the sampling rate should be at least twice maximum frequency of soundwave being sampled.
What is MIDI?
It stands for musical digital interface which is a system that allows electrical musical instruments and computers to send instructions to each other.
What are advantages of MIDI?
-Can easily synthesis musical notation from it
-Can be played on different instruments
-Produces relatively small file
-Easy to manipulate data
What is stored for a MIDI file?
-Length of note
-Instrument
-Velocity or speed
-Volume or amplitude
Why is streaming audio better than downloading a sound file?
-Less memory required
-Unlimited access to millions of songs
How does streaming work?
Audio and video is broken down into data packets, each packet contains small piece of file and client device takes flow of data packets and interprets them as video or audio. Information not stored locally.
How do you calculate size of a sound file?
Sample rate x duration x sample resolution
What is compression?
The art of minimising storage space for audio data.
