3DTV and Bandwidth1/16/2010 2:00 AM Eastern
Speaking of 3DTV, the darling of this year’s Consumer Electronics Show: It all seems very … 2004. That was the year anyone trekking around the Las Vegas Convention Center saw something new and shiny and everywhere. It was called HDTV.
At the time, and from the perspective of anyone in the bandwidth business, big questions loomed around the bandwidth-gobbling implications of high-definition television.
Refresher: HDTV images contain six times the picture information of standard-definition digital TV. Even with compression (MPEG-2), six times the picture info meant that only two, maybe three, HDTV video streams could shimmy into the same channel width (6 MHz) that carried 10 to 12 standard-definition streams.
It was (and is) a big deal. Cable responded, with analog spectrum reclamation, switched digital video, and 1-Gigahertz upgrades. (Whew.)
Now here comes 3DTV — which is essentially two HDTV streams, one for each eye. Double the bandwidth. Right?
Kind of. This week’s translation isolates just the transport part of 3DTV — because heaven knows there’s lots of moving parts in this next chapter.
The buzz at CES, from a transport perspective, emerged in lingo like “frame compatibility” versus “full resolution.”
Here’s what that means: In order to get 3D signals over the plant, in a bandwidth-friendly way, it’s necessary to wriggle both “frames” — the images for each eye — into one frame. People tend to call this “over/under” or “side-by-side.”
In all cases, it describes how the frames are jammed onto the conveyor belt, so to speak — one frame over another, or one frame next to the other.
To the network, “frame compatibility” makes a 3D signal look like 2D. The 3DTV knows what to do with each kind of incoming 3D frame, to pop it back out on the screen in 3D.
Either way, it’s another simulcast, on top of SD and HD.
The drawback, from a purist perspective, is that the encoding into side-by-side or over/under necessarily means that each frame offers less than “full resolution” to each eye.
Blu-ray Disc, an optical media, does offer full-rez to each eye, which is why you’ll see a big push, later this year, for 3D Blu-ray players and titles. (Think Avatar in your living room.)
The good news is that the frame compatibility exists, and that 3DTV manufacturers already support decoding of all types, which means there won’t be a “format war” — at least not on this part of the 3D food chain.