Coding for videoconferencing (H.261)

Abstract

The aim of this book is the introduction to the fundamentals of video coding standards, rather than giving instructions on the details of a specific codec, we concentrate on the reference model (RM) codec. The RM is a software-based codec, which is devised to be used in laboratories to study the core elements as a basis for the design of flexible hardware specifications. During the development of H.261, from May 1988 to May 1989, the RM underwent eight refinement cycles. The last version, known as reference model eight (RM8) [2], is in fact the basis of the current H.261. However, the two may not be exactly identical (though very similar), and the manufacturers may decide on a dif ferent approach for better optimisation of their codecs. Herein we interchangeably use RM8 for H.261. Before describing this codec, we will first look at the picture format, and spatio-temporal resolutions of the images to be coded with H.261.