4.5.6 Representing images, sound and other data Flashcards
What is a Bitmap Image made up of?
Bitmap images are made up of pixels.
Define Pixel.
The smallest unit of an image, representing a single point with a specific colour and brightness.
What is the equation for image file size?
image file size = colour depth x image height(px) x image width(px)
What is Analogue Data?
Analogue is a continuous set of values.
What is Digital Data?
Digital is a discreet set of values.
Define Colour Depth.
A measure of the amount of colour used in an image, expressed in terms of the number of bits used to represent the colour of each pixel in an image.
What is the number of colours that can be represented in a colour depth of 4? And how many bits are used?
2^4 = 16 colours
2^2 = 4, so 2 bits.
Define Metadata.
Data related to the image file data itself. e.g width, height, colour depth
Define Resolution.
A measure of the total number of pixels in an image, typically expressed in terms of the number of dots/pixels per inch.
How do you add more colours to an image?
Add more bits per pixel.
Define Sample Resolution.
The number of bits used to represent a single sample.
Define Sampling Rate.
The numbers of samples taken per second/over a given period of time.
The frequency at which samples are taken.
On the x axis.
Define Sound Sampling.
The process of converting analogue sound waves to a digital waveform, by storing a finite number of readings in binary.
Define Audio Bit Depth.
The number of bits used to represent the amplitude of each audio sample, affecting the sound quality and dynamic range.
On the y axis.
Define Amplitude.
The height of a sound wave, determining the loudness of the sound.
Define Frequency.
The number of cycles of a sound wave per second, determining the pitch of the sound.
Define Character Code.
The unique number used to represent a character.
What is an Analogue to Digital Convertor used for?
Used to convert the sound waves to a digital format.
What does the quality of the sound conversion depend on?
- sample interval
- sample resolution
How does the sample rate affect quality?
The sample rate allows the measurement of the frequency of a wave. The more samples the more accurate the tone is.
How does sample resolution affect quality?
The sample resolution allows the measurement of the amplitude of a wave. The higher the bit depth the more accurate it is.
Describe the process of analogue to digital conversion.
- Microphone (sensor) detects/ measures the analogue wave.
- The sound wave is sampled at regular intervals.
- For each sample the amplitude is measured.
- This is converted into discrete binary values.
- The values are stored in a sound file.
Define Sampling Error.
When the sample of the amplitude is incorrect.
Define Encryption.
Encryption is the process of scrambling data so that it cannot be understood by another person unless they know the encryption method and key used.
Define Decryption.
