ITU-R Working Party 6C's job is to agree 'baseband' formats for new video and audio systems that will be used in the broadcasting and media environments. The group, which met in September 2011, has a series of successes to live up to, which include the format used throughout the world for digital television, ITU-R Rec 601, and the Recommendations which define the HDTV formats. The challenge today is to prepare Recommendation for the new world of 'beyond HDTV'. There are two elements to this. The first is 3DTV. The second is Ultra High Definition Television.
The focus in WP6C on 3DTV is on the programme production and exchange format. Though in an ideal world there would also be a single worldwide standard for broadcasting 3DTV this is looking increasingly unlikely because systems need to fit with the legacy of earlier digital television broadcasting systems. This is just one more example of how legacies of differences reach down through the years. Today, for example, we have 50Hz and 60Hz television systems because of differences in electricity mains frequencies chosen 100 years ago.
Two ‘Special Rapporteurs’’ on 3DTV have worked over the past year on what needs to be done to facilitate the making and exchange of TV programmes in 3DTV. In general, their conclusion is that the basis of the production format should be a pair of one of the existing HDTV production formats. The work will continue between now and the next meeting of WP6C in spring 2012.
The work on Ultra High Definition Television focuses on the preparation of a potential Recommendation for the format of the ‘4K’ and ‘8K’ UHDTV systems. These have progressively 8M pixels per image and 32 M pixels per image. The number of pixels for these formats has previously been agreed, together with an ‘extended colour range’. At the current meeting, there was progress in agreement on the number of pictures per second that these systems should permit. The existing picture rates should be allowed, with the addition of 120Hz. This should make a substantial different to ‘motion portrayal’.
At the current meeting, the main area of discussion was however what is termed the ‘colour encoding’. This is the way that, when needed, reduced bandwidth signals are derived for the benefit of processes in programme production, and for eventual compression for broadcasting or other form of delivery. The objective of the colour encoding is to reduce the bandwidth either by a half or a third without the image quality being affected. This is possible because the eye is less sensitive to colour than to brightness, and the colour encoding exploits this.
Two colour encoding approaches have been discussed in the ITU. Both have advantages, but in different circumstances. The meeting finally agreed to establish a Rapporteurs Group to evaluate the two approaches side by side. This will hopefully lead to a conclusion about whether one or other colour method should be used exclusively, or whether they could both be options without dramatically affecting the overall quality the viewers will see.
During the meeting, NHK gave demonstrations of the 8K UHDTV system for delegates, and this helped to focus attention on this subject which is critical for the future of broadcasting.