Overview

In January 2003, BBC R&D produced a prototype video coding algorithm, based on wavelet technology, which is different from that used in the main proprietary or standard video compression systems. Our algorithm seems to give a two-fold reduction in bit rate over MPEG-2 for high definition video (e.g. 1920x1080 pixels), its original target application. It has been further developed to optimise it for internet streaming resolutions and seems broadly competitive with state of the art video codecs.

At the moment the codec, called Dirac, is in the early stages of development. It has been developed as a research tool, not a product, as a basis for further developments. An experimental version of the code, written in C++, was released under an Open Source licence agreement on 11th March at http://sourceforge.net/projects/dirac.

The philosophy behind the Dirac codec is “keep it simple”. This is an ambitious aim since video codecs, particularly those with state of the art performance, tend to be fearsomely complex. However, the BBC would like to collaborate with the Open Source community, academics and others to produce an open codec. It is therefore important for us to keep the principles and design as simple as possible and to provide copious documentation.

A lot remains to be done to convert our promising algorithm and experimental implementation into practical useable code. This includes optimisation so that it can decode in real time. Algorithmic enhancements are needed to improve the compression performance still further. The resulting codec needs to be integrated with other parts of a compression system, such as players, and interfaced using standard IO formats. We welcome help and support in creating an open and freely available compression system based on this technology.