METHOD OF AND DEVICE FOR CODING A DIGITAL INFORMATION SIGNAL

摘要

The invention relates to the coding of digital information signal blocks comprising representation symbols, such as sampled values, by means of an adaptive variable-length coding, such as Huffman coding. The JPEG Standard also utilizes adaptive Huffman coding but the coding in accordance with this standard is inefficient when a comparatively large number of Huffman coding tables are to be transmitted. According to the invention, in the case of a small number of representation symbols per information signal block, the probabilities of occurrence of each of the representation symbols are transmitted together with the variable-length-coded representation symbols, a similar (de)coding table being generated both in the encoder and in the decoder on the basis of said probabilities. In the case of a larger number of representation symbols per information signal block information about the number of code words of each length and/or the maximum code length in each series of variable-length-coded representation symbols is added to this series. By means of this information the decoder can unambiguously generate a coding table. The invention provides a substantial reduction of the number of bits required for specifying the Huffman code tables.