The above selection of input video sequences dictates the selection of the video coding standard. The main candidates are MPEG4 and H.263, as MPEG1 and MPEG2 are aimed at the coding of at least TV-quality images for entertainment video, and H.261 considered more suitable for circuit switched networks, such as ISDN.
MPEG4 was initially designed for very low bitrate communications, but on the way, it supported much more input formats. Now it is envisaged more as a complete integrated multimedia platform, which supports interactions between all the media streams. Examples include overlay text and graphics information which is changing according to the displayed video context, and could point to further information via the Web.5.2 MPEG4 is still in the standardisation process -- in the final stages, though -- and its main architecture has been changed from a simple scheme implementing cutting-edge technology to a versatile and highly modular scheme which accommodates a wide range of interactive multimedia applications.
On the other hand, H.263 is much more compact as a concept and has a restricted range of applications. Very low bitrate applications are destined to mobile multimedia applications, and there is a global research effort on adapting H.263 for mobile networks, which has resulted to an updated specification called H.263+. However, it emerges as a more efficient and economic candidate than MPEG-like schemes for personal communications and videoconferencing over wide area computer networks, as well. In fact, the standard caters for different network requirements, as the implementations are free to include or omit the optional parts of it.
From the above discussion, it has become clear that the H.263 standard was selected for video coding. This selection, has practical advantages as well, as there are public domain implementations for the specific standard, available at the source code level. One of them, the Telenor TMN5, was used for the implementation stage of this work.