FamousWhy Editor:
Arcode is the Python version of 'Arithmetic coding and decoding' which is an ANSI C compression implementation of the arithmetic coding algorithm.
Arithmetic coding is a form of variable-length entropy encoding used in lossless data compression. Normally, a string of characters is represented using a fixed number of bits per character, as in the ASCII code.

When a string is converted to arithmetic encoding, frequently used characters will be stored with fewer bits and not-so-frequently occurring characters will be stored with more bits, resulting in fewer bits used in total.

Python is a general-purpose high-level programming language whose design philosophy emphasizes code readability.

Python aims to combine remarkable power with very clear syntax, and its standard library is large and comprehensive.
Arcode is similar to Huffman coding; they both achieve their compression by reducing the average number of bits required to represent a symbol. In computer science and information theory, Huffman coding is an entropy encoding algorithm used for lossless data compression.

Features:

- Encoding Strings - By assigning each symbol its own unique probability range, it's possible to encode a single symbol by its range;
- Decoding Strings - The decoding process must start with a an encoded value representing a string;
- Order-n Models - This arithmetic coding algorithm is an order-0 zero algorithm. The probability ranges for a symbol are dependent upon 0 preceding symbols.

- Computing Probability Ranges – The developers have implemented both static and adaptive order-0 probability models.
- Limiting Computations to N Bits – This software has a way of representing floating point values as an infinite stream of bits and another way of scaling our probability ranges to N - 2 bits, so it can encode and decode using the scaled values
- Stopping the Encoding Process
- Stopping the Decoding Process
- Static vs. Adaptive Models - The arithmetic coding algorithm is well suited for both static and adaptive probability models
- Portability – The software should build correctly on any machine with an ANSI C compiler
The developer admits that the Python code was tested using Python 2.6 on Linux and Windows XP, so it is still possible that minor tweaks will be required to get the code to run properly using other versions of Python.

Why is Arcode famous?

Arcode is a Python library that includes a class implementing arithmetic coding and decoding. This implementation doesn't intend to be the best, fastest, smallest, or any other performance related adjective but it still is one of the best.

Publisher: Michael Dipperstein

Tags: arithmetic coding, compress files,