DIGITAL TERRESTRIAL TELEVISION
PICTURE FORMAT ISSUES
By Keith Malcolm
Executive Summary
This paper aims to provide explanatory material to assist in understanding of the technology issues involved in consideration of digital TV issues.
The paper provides an outline of the development of digital and HDTV technologies and then moves on to an outline of picture quality and video compression matters with a focus on the MPEG-2 standard which has achieved international recognition as the standard for entertainment video coding. The following section of the paper outlines some matters that influence the viewer's perception of picture quality and discusses aspects of the differences between HDTV and SDTV.
The paper then considers modulation issues in terms of available modulation systems and capacity of existing TV channels. At present, selection of a digital TV technology requires a choice between the USA's 8-VSB modulation system or the European COFDM system.
A further item to be considered is that of picture format, especially choice of picture scanning structure and aspect ratio. A choice needs to be made between HDTV or multiple standard definition programme capability. Because of the adoption of MPEG-2 coding, a choice in favour of HDTV capability automatically provides a reserve capability to deliver standard definition multi-programming, but a preference for multi-programming may "lock out" a future option for HDTV
There is brief discussion of some further aspects of choice of coding and modulation systems and an outline of developments overseas. The paper closes with an outline of issues that require some decision as a part of the process of consideration of DTTB matters (eg: progressive vs interlaced scanning, scanning format (1080 vs 720 vs 576 lines) and HDTV vs multi-programme).