The Digital Video Broadcasting Project has ratified specifications for the delivery of ultra-high-definition television services. Its Phase 1 specification sets a base level for UHDTV but does not address more demanding requirements that are already on the horizon. The DVB has also approved specifications for synchronisation between broadcast services and companion devices and a profile of MPEG-DASH adaptive streaming for use over internet protocol networks.
The DVB-UHDTV Phase 1 specification covers a resolution four times that of 1080p HDTV, with 10 bits per pixel, at up to 60 frames per second, using HEVC compression.
It allows for the possibility that Phase 2, which has yet to be considered, will use higher frames rates.
Phil Laven, chairman of the DVB steering board, said: “This new DVB-UHDTV Phase 1 specification not only opens the door to the age of UHDTV delivery but also potentially sets the stage for Phase 2, the next level of UHDTV quality, which will be considered in upcoming DVB work”.
With test transmissions already underway, including limited coverage of the World Cup football, the race is on to deliver the next generation of ultra-high-definition services.
Current efforts are mainly focussed on 3840×2160 resolution pictures, popularly but incorrectly referred to as 4K. An even higher resolution of 7680×4320 is also envisaged, sometimes referred to as 8K.
There is also a view that temporal resolution, with frame rates higher than 60 frames per second, may be as important as increased spatial resolution.
The ITU standard, generally known as Recommendation 2020, published in 2012, specifies both spatial resolutions at up to 120 frames per second.
NHK in Japan is planning to begin 7680×4320 ‘Super Hi-Vision’ satellite broadcasts as early as 2016.
Many broadcasters and consumer electronics companies currently see 2160p60 as a more practical format. The question is whether it simply represents an intermediate step to the ultimate in ultra-high-definition.
It is reminiscent of the introduction of high-definition television, when 720p and 1080i were advocated for practical reasons, rather than 1080p ‘Full HD’.
The DVB steering board also approved a specification for content identification and media synchronisation for companion screens and streams, otherwise known as A167-2.
This concerns the synchronisation of content on personal screens, such as phones and tablets, with related media on television devices, such as set-top boxes or network-connected televisions. This requires the identification of broadcast media and associated online material and the synchronisation of presentation on both screens.
Although conceptually simple, this is non-trivial to implement and integrate in broadcast infrastructures, which is why other workarounds have been used, such as audio fingerprint recognition.
Many broadcasters may have limited interest in the technical complexities involved. Yet the integration of experiences across different types of screen may be critical to their future.
The DVB also approved an MPEG-DASH profile for delivering adaptive bitrate media over internet protocol networks, in Bluebook A168. It includes support for UHDTV at up to 3840×2160 resolution at up to 60 frames per second.
The profile supports H.264 AVC and H.265 HEVC video compression. Conditional access is based on MPEG Common Encryption and delivery of subtitles in stream is based on XML.
The intention is to reduce the range of options available and so simplify implementation. However, ensuring reliable interoperability will remain a challenge, compared to existing broadcast standards.
All three specifications will go through to the European Telecommunications Standards Institute for publication as ETSI standards.