Lindsay Cornell, Principal Systems Architect, BBC and Chairman, WorldDMB Technical Committee
One of the functions of the WorldDMB Technical Committee is to develop new specifications and guidelines in Task Forces, and keep existing documents up to date. One Task Force that has just completed its work is “TF Hybrid Radio”, which has now been closed because the specifications it worked on have been published by ETSI.
TF Hybrid Radio was chaired by Nick Piggott from RadioDNS and its Terms of Reference were to integrate the required functionality for hybrid radio into the SlideShow and EPG specifications. In headline, that meant producing specifications that respected the needs of the existing digital broadcast ETSI specifications and those of the RadioDNS applications RadioVIS and RadioEPG. The task was both aided and complicated by the reality that these latter documents were based on the ETSI specifications, but had some additions for the extra IP functionality, and had removed some of the broadcast required features. In parallel, the core RadioDNS look-up was also being made ready for ETSI standardisation.
One of the key drivers for the hybrid specification work was to create better tools for broadcasters and device manufacturers to deliver a more visual experience of radio, especially on phones and tablets, where touch screens with icons, rather than buttons and text, are the way to navigate. With this in mind, the name Electronic Programme Guide (EPG) was felt to be off-putting and so it has been replaced with Service and Programme Information (SPI), which better reflects what it is for. The opportunity was also taken to add functionality, so that the SPI can provide both forward and backward programme information for both linear and on-demand content, whether delivered by broadcast (including filecasting) or IP.
The RadioDNS applications, RadioVIS and RadioEPG, rely on the RadioDNS core look-up, which provides standard methods to transform broadcast metadata into web addresses. In the process of bringing these applications into the hybrid specifications for SlideShow and SPI, some additional parameters were defined in the core look-up specification, moving them from the application specifications. This now means that whatever method is used to access the IP based elements of the hybrid radio experience, all the methods are defined in one place. This will help with ensuring that the hybrid experience is consistent.
The hybrid SlideShow is the combination of the broadcast SlideShow and the RadioVIS specifications into a single document. Quite a lot of restructuring was required to specify the common features clearly and separately from the broadcast delivery and IP delivery requirements. Of note in the new specification are the AlternativeLocationURL parameter, which allows connected devices to request customised images via IP (aspect ratio, resolution, etc.), and the ClickThroughURL parameter, which allows connected devices to access content related to the image by opening a browser window with a specified URL. The Categorisation, which allows broadcasters to allocate slides to topic areas, is still included, and these slides, too, can be delivered either by broadcast or IP.
The hybrid SPI is the combination of the broadcast EPG and RadioEPG specifications into a single document defining the XML representation of service and programme information. As with the hybrid SlideShow, there are common definitions for the XML and then separate clauses to describe the broadcast and IP requirements. The SPI metadata is divided into files and can be delivered by broadcast and/or IP in many different combinations; for example a broadcaster may choose to deliver the Service Information files via his DAB service, but provide the Programme and Group Information files only by IP. For broadcast delivery, the files are compressed using the companion transport and binary encoding specification, which has been rewritten to reflect the new XML structure. In this way, any existing EPG decoder will be able to make sense of the original features of the metadata described by the new SPI XML (but of course will not be able to provide the new features, like on-demand content, because these elements were not known previously.)
The four specifications published by ETSI in January are:
For further information on the WorldDMB Committees and Task Forces, visit the WorldDMB website.