For those of you who are not familiar with the term “service compatible,” this refers to a new broadcast standard that could augment, and maybe replace, the current 3D broadcast standard called “frame compatible.” The frame compatible format has allowed cable and satellite providers to deliver 3D content to 3DTVs with minimal upgrade to their existing infrastructure. But there are trade-offs to this approach, which service compatible formats will address – and may be the key to broader acceptance and viewing of 3D content.
The frame compatible format takes full resolution left and right eye images and packs them together into a single video frame. The most common formats are side-by-side and top/bottom. This approach reduces the resolution of the original stereo pair so that the decoded 3D image will have some loss of fidelity when viewed on the 3DTV. Several companies have proprietary methods to reduce fidelity loss, but these do not seem to be widely used at this time.
The other big trade-off with frame compatible is that the 3D signal is not viewable on a 2D set — you will see a side-by-side or top/bottom formatted image. Therefore, 3D content must be broadcast on a separate channel from the 2D version – thus doubling bandwidth and creating separate telecasts that are less accessible and visible to consumers.
The service compatible formats under consideration in various standards bodies address the two primary issues of full resolution to each eye and the need for a second broadcast channel.
While a number of formats are under consideration (more details are available in our IMU course on the topic), MVC (Multi-Video Coding) is now the frontrunner within the DVB standards-setting task force, said David Wood, deputy director of the European Broadcast Union Technical Committee in an email to Insight Media. MVC is the standard used to create Blu-ray discs. To encode a 3D movie, the codec first calculates the “difference” between each pixel in the left and right eye images. The metadata representing this pixel difference is then attached to the original left eye image and encoded into an mpeg stream that is recorded on the disc. The Blu-ray player decodes this and restores full resolution left and right eye images to offer 3D signals for a 3DTV, or the original left eye image for a 2DTV. 3D Blu-ray is the image quality standard for 3D today.
To adapt MVC for broadcast, Wood noted that, “MVC is a specification already done in MPEG so we don’t need to wait… we just have to add appropriate signaling.”
Note that a broadcast version of MVC will deliver full resolution per eye, and allows a single stream to deliver both the 2D and 3D versions of the content. However, the service compatible system will require the deployment of new set-top boxes – an infrastructure investment.
Cable and satellite operators will only consider such a rollout if they think it will have a return on investment. Improved delivery of 3D may be part of this equation, but other advanced features on new set top boxes could also sway the decision.
I also want to highlight a key point that Corning’s technology development manager, Robert Boudreau, made in an email exchange. His point was that in the transition from black and white TV to color TV, major shows were broadcast in color on the major networks to help spur adoption of the technology (remember Disney’s Wonderful World of Color?). Viewers saw an icon that identified the show as being broadcast in color, which was visible if you had a color TV, but shown in black and white if you did not. This created huge mainstream awareness of the color technology and a desire among consumers to upgrade their TVs.
The service compatible format has the potential to do the same thing for 3D. If major sporting events and prime time network shows were available in 2D or 3D on the same channel, this would make it a lot easier for the consumer to watch 3D content — and a greater array of high quality content.
Woods said they should have a draft service compatible document this summer, so rollout could not be that far away — at least in countries that use the DVB standard. The ATSC committees working on 3D and other advanced standards are likely looking closely at MVC, too.
So, the service compatible format, in combination with broader availability of 3D content, could easily combine for a second wave of 3D enthusiasm in 2013/2014.
Chris Chinnock is a senior analyst and editor from Insight Media. Reach him at firstname.lastname@example.org