Advanced sound potential for Ultra HD as DVB approves Phase 1 spec10 July 2014
With 4k TV sets already on the market and the likes of the BBC and Sony testing the technology on broadcasts of the World Cup, Ultra High Definition (UHD) already has a high profile. Last week an agreed UHD standard came a step closer to reality, which in turn would “unlock” 4k broadcasting, with the DVB (Digital Video Broadcasting) project approving the Phase 1 specification.
This first part of the DVB-UHDTV spec was announced in Geneva by the DVB Steering Board. It includes a HEVC (high efficiency video coding) Profile for DVB services with compression options that tally with requirements for delivering UHDTV Phase 1 and other formats. The specification is an update of ETSI TS 101 154, which covers the use of video and audio coding in broadcasting applications based on the MPEG-2 transport stream.
DVB-UHDTV Phase 1 will make possible the transmission of images with four times the static resolution of 1080p HD, at frame rates of up to 60 images a second. Contrast will rise through increasing the amount of bits per pixel to 10-bit. At present there is no agreement on an accompanying audio format but it is generally agreed by developers, broadcasters and standards bodies that this would be some form of spatial sound, delivering a sensation of height as well as width and length to match the more immersive nature of the pictures.
DVB Steering Board chairman Phil Laven comments, “HEVC is the most recently developed compression technology and, among other uses, it is the key that will unlock UHDTV broadcasting. 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.”
Phase 2 could include higher frame rates and Advanced Sound Systems (ASS), the umbrella heading for a variety of immersive surround sound formats that could be standardised for UHDTV. David Wood, chairman of the commercial module of DVB-UHDTV (pictured), says that as screen sizes increase there will be a need to give the viewer the ability to recognise sound directions in the vertical plane as well as the lateral, producing so-called 3D sound, which would come under the heading of ASS.
“The DVB Project, along with other bodies such as the ITU-R and MPEG, are studying ways of providing 3D sound with UHDTV,” he explains. “There are a number of ways of achieving the ASS. In the UHDTV home of the future you may find loudspeakers providing 3D audio in layers – floor, ear-height, and ceiling. Options [ to do this technically include] ‘object-based coding’, ‘scene-based coding’ and ‘‘discrete-channel coding’. Each has advantages and each will make different demands on the broadcast capacity needed and have implications for the placing of loudspeakers in the home. The DVB Project is currently examining case studies of the environments in which an ASS will be needed and be used, with the aim of examining when and how it could be included in a future UHDTV specification.”
Wood adds that ASS may be included in the DVB UHDTV Phase 2 specification, which is intended to be available for UHDTV broadcasts launched in 2017-18. “Much progress has been made in the standards bodies on 3D audio but there still remains a job to do before we hear birds fly from the bottom to the top of the screen,.” he says.