SLR1.2 part 2 Flashcards
images are stored in…
binary as bitmap or vectors
lossless compression
none of the data is lost, it is just encoded differently.
it can be turned back into its original format
can be used on all data types
not as effective at reducing file size compared to lossy compression
most suitable for documents and executable files
compression
reduces the number of bits in a file
this reduces the storage of the file lower
makes transferring of files faster
more data can be stored on a storage device
lossy compression
loses some of the data and cannot be recovered
greatly reduces the storage size
reduces the quality of images/sound
suitable for images, sound, video
not suitable for documents and executable files as some of the text would be lost
character set
a defined list of characters recognised by the computer. Each characters represented by unique binary number
examples of character sets
ASCII (7 bit characters et), extended ASCII (8 bit character set), unicode (24 bit character set)
bitmap
pictures that are made from coloured squares called pixels
vector
pictures that store the mathematics to draw the coloured shapes
the number of values in 1 bit
2 possible values, 0 and 1
sound is stored in binary through…
analog to digital conversion, where the sound is converted to binary to be stored
sound file size
total number of bits in a second
calculated as number of samples per second x number of bits per sample x length of sample in seconds
bit depth
the number of bits stored per sample
the higher the number of bits, the greater the quality of sound, the larger the file size
sample rate
the number of samples stored per second
the higher the number of samples per second, the greater the quality of sound, the larger the file size
metadata
additional data stored with the image to define its width, height, colour depth and colour palette.
e.g. the metadata of a document would be the name of the author
the number of bits on a photograph
24 bit colour pallete
calculating text file size
bits per character x number of characters
calculating image file size
colour depth x image height x image width
calculating sound file size
sample rate x duration in seconds x bit depth
how is sampling used to make a recording
amplitude of wave is sampled
Converted to binary
measurements taken at a regular interval
(eg 44,000 times per second)
sample frequency =
sample rate
