Data Compression Flashcards
Why do we compress files? (2)
-less storage space
-less network transition time
Differentiate between the two types of data compression and give an example of each
-Lossless: no data is lost, the file just becomes smaller. ex) pkzip
-Lossy: data may be lost ex) Jpeg, MP3
What are the 2 techniques of data compression, and are they lossy or lossless?
-both lossless
-Huffman (binary trees with characters as leaves, branches represent encoding)
-code dictionary (short, fixed code words)
How many bits does each character occupy?
8 bits = 1 byte
In huffman coding, the branches represent __, while the nodes leaves represent___.
encoding, characters
what are pixels?
Tiny dots of white, black, or colour arranged on screen
What are bit-mapped graphics/ raster graphics?
simple maps showing where pixels should go
What is resolution?
Number of pixels in total per square inch
vector/object-oriented graphics are?
images represented by geometrical formulas
Differentiate between JPeg and GIF compression
JPEG: complex, pictures, 24 bit (millions of colours), divides and processes images in 8x8 groups, quality factor, lossy
GIF: simple, cartoons, 8 bits (256 colours), map each colour to letter lossless
PNG
-replacement for GIF
-24 bit
-no printing, only transferring images via internet
Complex audio
-remove imperceptible sounds
-remove quiet sounds competing with loud
simple audio
-decrease sample bit depth or rate
What is an audio file determined by?
-sample rate (HZ)
-bit resolution
-time (s)
-channels (1= mono, 2= stereo)
