3-4: Images and Sound Flashcards
what does pixel stand for
picture element
smallest addressable part of an image
what is colour depth
the number of bits stored for each pixel which represents the colour
explain how bitmap images work
they are images stored in the computer memory as a grid of pixels - each pixel is stored as a specific colour
explain how vector images work
these images are stored as shape/objects using specific properties of the shape
eg, rectangle(2,2,8,8,light blue) - this means draw a rectangle with left corner 2,2 and top right corner 8,8 and fill w light blue
what is the resolution of an image
width of image in pixels x height of image in pixels
state 4 advantages of vector images
-does not deteriorate when enlarged
-usually faster to load
-usually uses less memory
-easier to edit
how do u convert an analogue sound to digital form
analogue to digital converter
ADC
how do u convert a digital sound to analogue form
digital to analogue converter
DAC
describe the process of a computer recording sound and then playing it through a loudspeaker
-microphone picks up the sound waves
-the sound wave is amplified
-an ADC converts the analogue signal to digital
-to play back the recorded sound a digital to anologue converter (DAC) is used
-the signal is then played through a loudspeaker
what are samples
measuring the value of the analogue signal at regular intervals
what is CD’s sampling rate
44,000 every second
44 kHz
16-bit amplitude
what is Nyquists theroem
the sampling rate should be at least double the highest frequency of the sound wave being sampled
what is MIDI
system that allows electronic musical instruments and computers to send instructions to eachother
give 3 advantages of MIDI
-can easily synthesise musical notation
-easy to manipulate data
-no data is lost
why is streaming audio sometimes preferable to downloading the sound file
less memory required
unlimited access
in simple terms, how does streaming work
the video loads a little bit at a time instead of the entire file loading at once and the information is not saved locally
explain the difference between an analogue signal and a digital
analogue is continuous and digital is discrete
what is the equation to calculate filesize of a sound
filesize = sampling frequency * bit depth * length
desribe the principles of operation of an analogue to digital converter
- the analogue signal is sampled at regular time intervals
- the amplitude of the signal is measured
- the measurement is then coded in binary
how do you calculate storage requirements for bitmapped images
width x height x colour depth
describe the difference between lossless and lossey compression
- lossey reduces a file size by eliminating certain information
- lossless keeps every bit of data originally in the file
how does MIDI represent music
- sequence of MIDI event messages
- one exampled of data that might be contained in a message is the volume
what is metadata and give an example
- data that provides information
- location, author, time it was taken
describe the principles behind the technique of run length encoding
- identifies sequences of identical data
- represents these as one data value with a count of how many such values are in the sequence
how do you convert bits into megabytes (MB)
- divide by 8
- divide by 1 000 000
