Adaptive Distribution

The adaptive coding procedure uses a code tree that is permanently adapted to the previously encoded or decoded data. Starting with an empty tree or a standard distribution, each encoded symbol will be used to refine the code tree. This way a continuous adaption will be achieved and local variations will be compensated at run-time.

Adaptive Huffman codes initially using empty trees operate with a special control character identifying new symbols currently not being part of the tree. This variant is characterized by its minimum requirements for header data, but the attainable compression rate is unfavourable at the beginning of the coding or for small files.