By Neil Schneider
One of the big trends of 2011 is the introduction of passive 3D HDTV displays for the consumer markets. Up until now, polarized televisions had premium pricing and were limited to either the professional or public display markets. LG Electronics has been taking the lead with transitioning their products to a polarized format for end-users, and with data from iSuppli, they are already boasting higher sales rates compared to their competition’s LCD shutter glasses counterparts in China.
For those unfamiliar, interlaced polarized displays work by vibrating light at two different wavelengths, and have the 3D glasses filter the images to the left and right eye independently. This offers a bright image with little to no ghosting or cross-talk. The only caveat is that most polarized displays work by dividing the vertical resolution in half, and reserve 50% of the lines for the left eye, and 50% for the right.
For stereoscopic 3D gamers and game developers, polarized solutions offer additional benefits that most aren’t aware of:
First, while the HDMI 1.4 specification used with modern 3D HDTVs is supposed to support 1080P at 60 frames per second in 3D mode, this is beyond the capability of current chipsets. For gamers, most 3D HDTVs with shutter glasses are limited to 720P resolution at 60FPS, and 1080P is capped at 24FPS.
Another benefit is the interface itself. While HDMI 1.4 is a standard connector, there is some secrecy in how it is accessed. This is why HDMI 1.4 compliance is only possible with Nvidia stereo drivers on Nvidia GPUs (3DTV Play), and DDD and iZ3D can only accomplish the same results through AMD graphics cards. In the case of interlaced polarized displays, game developers can write directly to the screen without any special pass-through with proprietary display drivers.
Before dumping your 3D HDTV or holding off on your next purchase, it’s important that we compare apples to apples!
LCD shutter glasses work in tandem with the screen where the left and right views appear one at a time: left view, right view, left view, right view, etc. The glasses blank out each eye in cooperation with the screen, and with the images appearing so fast (60 times per second per eye), your brain forms a full stereoscopic 3D image. Shutter glasses are always full resolution per eye – not 50% of the vertical lines that interlaced polarized displays offer.
PC Gamers can rejoice, because most 3D HDTVs offer a side by side or above below mode. In this case, the image is sent to the display in a “squished” side by side mode, the TV extrapolates what the left and right view should look like, and scales to the correct proportions. This means that with the same amount of 2D bandwidth, gamers can enjoy 1080P gaming at 60FPS. Even though 50% of the data is lost, the television’s scaling is very good. Both DDD and iZ3D stereoscopic 3D drivers support these modes, and work equally well on AMD and Nvidia graphics cards.
What does this gobbledygook all mean? Whether you are using a passive display or a shutter glasses display, there are still ways to get 1080P output and have direct access to the screen at 60FPS regardless of HDMI 1.4 compliance.
Unfortunately, while gamers hold all the cards with both 3D display options, broadcasters have reason to be concerned about interlaced passive displays. At this time, the current 3D broadcast standard is a squished side by side mode that scales through the television. They are doing this because they don’t want to invest money in doubling available broadcast bandwidth through satellite and cable networks. For shutter glasses displays, this is a nuisance, but not a deal breaker. Interlaced passive displays are more problematic.
The current “squished” side by side mode already begins with a 50% loss of horizontal line resolution so that the 3D frame can fit in a 2D screen. Polarized displays lose even more resolution because 50% of the vertical resolution is reserved for the left and right view. Once the images are scaled to compensate for all this missing data, the broadcasts can have a grainier appearance.
The solution is to either change the entire standard to an above/below format so that interlaced displays aren’t disadvantaged, or for the industry to quickly choose and implement a compression format like those offered by Sensio and TDVision Corp. It’s important to remember that the HDTVs need to have the codec in their firmware or chipset as well!
The moral of the story is there is still standards work to be done – especially in broadcasting. Should the industry switch to an above/below format? Will this improve passive display quality and inadvertently undermine shutter glasses quality? What’s the solution?
Share your thoughts!