1.07 - Compression techniques Flashcards
What are the two types of compression techniques?
Lossless and Lossy compression
Why are compression techniques used?
To reduce file size and improve transmission or download rates
Define Lossless compression
It reduces the file size without losing any information and can be reversed to recreate the original file.
Define Lossy compression
It reduces file size with some loss of information and the exact original file cannot be recovered
How do good compression applications work?
They recognize patterns in files that can be compressed without the knowledge of the file type. Most compression tehniques have been developed to work with particular file types
What are the types of Lossless compression techniques?
- Run length encoding
- Huffman coding
Which compression technique is used to compress bitmap files?
Run length encoding
Which compression technique is used to compress text files?
Huffman coding
Which compression technique is used to compress sound files?
Huffman coding
How to compress a vector graphic file?
Convert it to Scalable Vector Graphic format. This uses a markup language description of the image which is suitable for lossless compression
When can lossy compression be used?
When some of the detailed coding can be removed or modified without being noticed by the human ear or eye
One method of lossy compression for sound files takes advantage…
…of the fact that successive sampled value are unlikely to change very much
How are bitmaps compressed using lossy compression?
A simple lossy compression technique establishes a coding scheme with reduced colour depth and changes the code for each pixel to the one in the new scheme that represents the closest colour
