Contents

1 Intro

• Created by Microcom Inc. for the MNP (Microcom Networking Protocol) 5 [1].
• Does not expand the small runs (smaller than 2 symbols).

2 Codec

• The behavior of the codec can be easily defined with the following examples:

  Input	Output	Comment
  ab	ab	No encoding
  aab	aab	No encoding
  aaab	aaa0b	Expansion :-(
  aaaab	aaa1b	Encoding, but not compression
  aaaaab	aaa2b	Compression
  a${}^n$b	aaa$n-3$b	The general case

  where a${}^n$b is a string of $n$ consecutive a and $n$ is a binary code of a fixed length.

Example

The runs:

are encoded as:

Let’s go to the lab!

1. Download http://www.ace.ual.es/~vruiz/doctorado/text-compression.tar.gz and make rle.
2. Download The
   Image Compression Corpus:
3. Encode each image using the RLE codec. Build the table:
   
   Codec | lena boats pepers zelda Average  
   ------+--------------------------------  
     rle | ....  ....   ....  ....    ....

   where .... is the compression ratio computes as:

   $$\gamma =\frac{X}{Y}$$

   (1)

   where $X$ is the size of the input (the sequence of symbols) and $Y$ the size of the output (the code-stream).

4. Any compression?
5. Verify that the codecs are lossless!

References