SPEECH AND IMAGE-CODING FOR DIGITAL-COMMUNICATIONS

The paper is presenting a sketch of the main results achieved in the recent years and of the ongoing activities (mainly within the Standardization Bodies) in the areas of audio and video coding for bandwidth reduction. The evolution of the telecommunication field and the needs which originate the different standards are also considered. The paper is organized in two main chapters: the first one is dealing with the techniques for audio and speech coding while the second presents the main achievements in terms of Recommendations and consolidate algorithms for image coding. Concerning speech and audio coding the paper presents and overview of the coding techniques and then examines the different environments of transmissions (network and mobile communication), the bandwidths required to satisfy the considered applications and the defined speech quality evaluation methods. A similar approach has been used for video coding and the evolution of the coding techniques appearing in the CCITT Recommendations is presented. The ongoing activities within CCIR, CMIT, CCITT and ISO towards new worldwide standards are also outlined providing indications on the areas which will require further developments.