Impact of Second-Gen 3DTV on STB
Pay TV operators are the ones who will have to prove the viability of 3DTV to the home and while they are creating a market for the new services, Frame Compatible 3D technology means they can use their existing HDTV infrastructure (particularly encoders and set-top boxes) and avoid significant investments.
However, the wider broadcast industry is openly discussing whether there is a need for a second generation 3DTV transmission technology and what form it should take, with some broadcasters keen on Service Compatible 3D (where the 2D and 3D services are transmitted in a single signal and 2D set-tops can view the content in 2D while any new 3D STBs produce 3DTV content).
We asked a leading video SoC (Silicon on Chip) vendor, Sigma Designs, about the implications of ‘second generation’ 3DTV transmission technologies on the set-top box. Vincent Harradine, Director of Systems Engineering at the company, provides the answers.
What is the impact on customer premise equipment of frame compatible 3DTV services?
One of the main reasons for the existence of such frame compatible formats is their ability to be supported by existing/legacy infrastructure and equipment such as set-top boxes. An existing set-top box can support the decode and output of 3DTV frame compatible formats, e.g. side-by-side or top-and-bottom. Frame compatible formats do not require any additional processing or formatting beyond decoding.
Dependence is upon the display device, e.g. 3D TV, to take care of formatting to typically a frame sequential or page flip format for display. Additionally, the latest HDMI 1.4a specification includes such frame compatible formats as mandatory, plus all 3D TVs currently available are forced to receive and display such frame compatible formats.
All of this can be achieved without any firmware update to the STB but does rely on the customer having a 3D ready TV.
Can existing HD STBs support full 1080p50/60 HD if platform operators wanted to improve the quality of 3D television by increasing the quality of the HD used in frame compatible mode?
Two main issues result in 1080p50/60 support not being readily available with today’s STBs. First, the lack of current video decoder SoC device support for the decoding of 1080p50/60. Second, the HDMI transmitter physical layer being restricted to a maximum pixel clock rate of only 74.25MHz, which is insufficient to support the 1080p50/60 pixel clock rate of 148.5MHz.
What are the key challenges in enabling set-top boxes to support full 3DTV? What is the likely premium for such set-tops? When are we likely to see them?
Support for full 3DTV will require new STB hardware allowing for the support of the appropriate 3D format (e.g. base layer plus enhancement or 2D plus metadata) along with HDMI transmitter support for the necessary data rate increase. Initially there could be a market for such a premium or high-end full resolution STB box. However, over time it will likely become mainstream especially as consumers become aware of the quality difference between BD [Blu-ray disk] (MVC full 3DTV) versus frame compatible (e.g. side-by-side) for the same content.
What challenges would 2D + Delta provide in the STB if operators used this to enable one video stream that could be used for 2D television on 2D STBs and 3DTV on 3D capable STBs?
Typically today’s SoC decoder/media processors are incapable of support for the decoding of 2D + Delta. This means STB upgrades would be necessary; in the absolute best case a firmware upgrade may suffice but in most cases it would require new STB hardware. 3D signalling would also be a necessary requirement, allowing for the appropriate handling of content in 2D versus 3D environments.
Do you think using a single signal for 2D and 3D is realistic - or are 2D and 3D television too different creatively (e.g. camera positions, the way content is shot) for this to work?
For the vast majority of content this will work. Issues could potentially arise over content shot for large screen (movies) versus small screen (TV). But then this is the basis around the selection of MVC as a coding format for Blu-ray (BD) where, in theory, 3D BDs should be capable of playback on existing 2D systems by displaying the single full frame image.
What challenges would 'frame compatible plus enhancement' have for the STB (where frame compatible 3D can be viewed on a normal HD set-top box, as today, but an enhancement layer can also be used to create full 3DTV from the same signal in homes where new, full 3DTV STBs are deployed)?
Today’s STBs are not capable of supporting frame compatible plus enhancement without at least a firmware upgrade. Even a firmware upgrade is a very remote possibility. Almost certainly, new STB hardware will be necessary to allow for such support. Once again, appropriate 3D signalling must be standardized and realized, allowing for hands-free handling of such content.
How realistic is Multiview Video Coding (MVC), as seen in 3D Blu-ray players, for set-top boxes? What cost premium is there compared to standard HD video decoding? When could MVC be supported in STBs?
Sigma Designs will have silicon available in the fall that supports both frame compatible and full 3DTV formats, such as MVC, so it is likely such STBs could become available during 2011. Due to the decoding and subsequent management of two full left and right images, the need for memory bandwidth increases accordingly. This has the potential to increase the BOM [Bill of Materials] cost of STBs. However in the case of the Sigma Designs solution, we have the means for intelligent handling of data for more efficient management of the increased data bandwidth.
By John Moulding, Videonet
