5.6 Representing Images, Sound and Other Data Flashcards
(23 cards)
Which type of signal is shown here?
Digital signal
What two things are true of a cipher that is computationally secure?
The cipher can be cracked.
But not within a reasonable timeframe given current computing power.
What device can be used to convert a signal from analogue to digital?
An analogue to digital converter (ADC)
What is the most common use for an ADC?
Converting digital audio signals to analogue signals.
What name is given to the process of reading an analogue signal at regular intervals and recording values?
Sampling
What is the unit for sampling frequency?
Hertz (Hz)
State two disadvantages of MIDI.
MIDI can’t be used for storing speech.
MIDI sometimes results in a less realistic sound than sampled recordings.
What type of data compression is run-length encoding?
Lossless compression
Which type of data is continuous?
Analogue data
Give two examples of typical metadata for an image.
Examples include width, height, colour depth, and date created.
Which two criteria must be met by a key if it is to be used in a Vernam cipher?
The key must be random.
The key must be at least as long as the plaintext.
Which type of image can be scaled without losing quality?
Vector graphics
Which type of Caesar cipher is most easily cracked: shift ciphers or substitution ciphers?
Shift ciphers
Which rule states that the sampling rate must be at least twice the frequency of the signal?
The Nyquist Theorem
What does MIDI stand for?
Musical Instrument Digital Interface
Name two types of data compression.
Lossy compression
Lossless compression
How does MIDI store sound?
Using a series of event messages.
Which type of image is used for storing photographs?
Bitmapped graphics
With which type of data compression does the quality of a file remain the same?
Lossless compression
Which type of cipher encrypts information by replacing characters?
Caesar ciphers
How do bitmap graphics work ?
image is broken down into pixels, each of which has a
binary value assigned to it.
What is a pixel ?
The smallest addressable part of a bitmap image
How do vector graphics work ?
Represent images using geometric objects and shapes
