CS101.Lect13.Compression.ppt

CS101.Lect13.Compression.ppt - CS101 Lecture 13:...

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1 1 Aaron Stevens 18 February 2011 Some material form Wikimedia Commons Special thanks to John Magee and his dog CS101 Lecture 13: Compression Techniques 2 What You’ll Learn Today – Review: how ASCII works and the great unfairness of bits – What are the main strategies for compressing data? – Examples of compression algorithms
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2 3 Data Compression (saving space) Data compression Reduction in the amount of space needed to store a piece of data. Data compression techniques can be: lossless , which means the data can be retrieved without any loss of the original information lossy , which means some information may be lost in the process of compaction 4 Example: Text Compression Problem: Unicode assigns 16 bits to each character in a document; uses a heck of a lot of space. We need ways to store and transmit text efficiently. Why? Common lossless compression techniques: keyword encoding run-length encoding Huffman encoding
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3 5 Keyword Encoding Replace frequently used words with a single character 6 Keyword Encoding Example Given the following paragraph, We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life,
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This note was uploaded on 12/16/2011 for the course CS 101 taught by Professor Stevens during the Spring '08 term at BU.

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CS101.Lect13.Compression.ppt - CS101 Lecture 13:...

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