3D Vision Blog

You should be well aware of the fact that transmitting stereoscopic 3D content over a video interface requires more bandwidth and depending on the interface and the type of 3D content the required bandwidth is usually twice more, or a bit less, than that needed for sending 2D content. I’m talking about sending uncompressed images for both left and right eyes of course as there are some solutions that use compression to save bandwidth, as using compression might increase the price and complexity of the product and add some delays, but this however is something that is not good to have when talking about 3D displays. And here I’m going to be talking about what is the possible near future of 3D displays and more specifically 3D monitors intended for use with computers…

Currently all more recent 120Hz 3D monitors use Dual-Link DVI as an interface for transferring stereoscopic 3D data from the computer to the display using frame-sequential mode. These are of course LCD monitors using faster panels that can work with 120Hz refresh rate, so with a pair of active shutter glasses you are able to split the sequence of images being displayed into a left/right pairs and thus allow the user to see 3D with 60 frames per eye. The alternative is to use a 3D display with passive polarization in order to save bandwidth, but then you will also have some loss of resolution and thus you loose a bit of the quality in 3D mode and that is considered as a somewhat of a compromise and we don’t want to compromise with quality when talking about stereo 3D, right? Anyway, having a display working with 120Hz refresh rate at Full HD resolution of 1920×1080 pixels requires a lot of bandwidth and it pretty much fills in the capacity provided by the DL DVI interface (note it is Dual and not Single Link DVI). This is of course the current state of things with active shutter solutions, but what will happen in a few years when displays with higher resolutions start to appear and users would want to have faster refresh rate even in 3D mode? Obviously the Dual-Link DVI interface will not be able to do that job, so we’ll need another interface and we actually have that interface available for quite some time, it is called DisplayPort. An interface that can provide higher bandwidth and offer more for 3D-capable solutions, not to mention that it is royalty-free, unlike the HDMI interface where you have to pay for each device equipped with the interface as well an yearly fee to use the interface.

Mentioning the HDMI interface, I should go on a bit about it and especially regarding the HDMI 1.4 specification of the interface that was released in 2009 and later on updated to 1.4a in 2010. The HDMI version 1.4 specifications of the interface have introduced official stereoscopic 3D support and since then this has become the defacto standard for ensuring 3D compatibility and interoperability for 3D-capable consumer electronic devices. All of the recent 3D HDTVs, Blu-ray 3D players and so on use HDMI 1.4 interface and you can pretty much guess that none of them has a DVI interface, or a DisplayPort for that matter. HDMI is an interface developed and designed for and by the consumer electronics industry and while it is also going quite strong in the IT industry it is not going to replace more typical computer interfaces for video such as DVI. The computer industry’s counterpart for the HDMI interface is the DisplayPort, but unfortunately DisplayPort is still not that well developed and as commonly used as DVI or HDMI and that is still causing delays with the adoption. The major problem with the HDMI 1.4(a) interface is that it is more bandwidth limited and you cannot even have 1080p resolution in stereo 3D mode with more than 24Hz (24 frames per eye), a resolution/refresh rate combination that is ideal for 3D movies, but not that good for stereo 3D gaming. But since the development of the stereo 3D specs of this interface had to take into account the requirements of consumer electronics devices such as game consoles and Blu-ray players it has been decided that defining 720p 50/60Hz 3D mode and 1080p 24Hz 3D mode was enough. The PC has been completely left outside of the equation, so that Dual-Link DVI was the solution adopted for 3D monitors intended to be used with computers in order to provide up to 1920×1080 resolution at 120Hz (actually DL-DVI can support 1920×1200 @ 120Hz as well, but there are apparently no 120Hz panels to support that resolution).

Let us get back to the DislayPort interface as this is considered to be the new interface for 3D-capable monitors as it can even now provide much more than what HDMI and Dual-Link DVI interfaces are capable of in terms of bandwidth. DL-DVI is enough for the current generation of 3D monitors, but there are already people looking for 2560×1600 resolution and 120Hz refresh or asking about 120Hz refresh rate per eye in 3D mode and not only in 2D on Full HD displays. Such requirements are not possible unless DisplayPort is used and more specifically DisplayPort version 1.2 that has been approved in 2009, because earlier revisions of the interface are a bit more limited in terms of stereo 3D support. The truth is that DisplayPort was 3D-capable interface even back in 2007 when version 1.1a of the standard has been approved, but back then it was still way too new (the first version of the interface was approved in 2006). DisplayPort 1.1a had support for frame sequential stereo and could provide 1080p resolution with 60Hz per eye in 3D mode, but due to limited support of the interface on video cards back then DL-DVI was the preferred choice. Now the newer DisplayPort 1.2 has even better support for stereoscopic 3D displays and can provide up to 120Hz refresh rate per eye in 1080p resolution or 2560×1600 with 60Hz per eye in 3D mode. The 1.2 version of the interface supports not only frame sequential format, but can also work with Side by Side, Top/Bottom, Line and Pixel interleaved modes. There is also an enhancement of the EDID allowing display manufacturers to describe what is their 3D monitor using DisplayPort is capable of supporting in 3D mode, so that the capabilities of the display can be automatically read by the computer software.

If you are already wondering why in the hell there are no 3D monitors on the market that take advantage of all the extra capabilities that the DisplayPort 1.2 interface is offering there is a simple answer. The DisplayPort interface is still not that common enough and available on all more recent video cards sold in the last 2-3 years, so display manufacturers are still mostly adding that interface on higher-end products as an extra feature, but it is not yet considered to be of major importance. For example most of the latest video cards based on Nvidia GPUs still don’t come with DisplayPort on them as a standard feature, the situation with more recent AMD-based video cards is better as they all come with at least one DisplayPort interface on the backplane. But it is not only up to hardware, the software also needs to support stereo 3D over DisplayPort and the situation there is still not that good as well. AMD just recently introduced official support for stereo 3D over DisplayPort in their latest Catalyst Software Suite Version 11.9 that has been released a few days ago (there was beta support in an earlier preview driver, but users had problems making it work). But this support comes along after the recent release of the first 3D monitors equipped with DisplayPort interface and these are the Samsung 750 and 950 series of 3D-capable displays. Nvidia is a bit late on introducing stereo 3D support over DisplayPort interface, but there are also no 3D-capable monitors compatible with their 3D Vision technology being announced yet, so they are probably not in a hurry to do that like was in the case with AMD (the products were already on the market). But if you want a 240Hz Full HD LCD monitor or a 2560×1600 120Hz one you would still have to wait a bit more for software and for hardware to catch up with the specifics and requirements needed to support these as DisplayPort is just one of the things needed that is already available, but there are other requirements that still need to be fulfilled. I mean things such as faster response LCD panels as with the current generation of 120Hz TN panels we are still having issues with crosstalk/ghosting. Having a video card (you’d need multiple) that can push 240 fps in Full HD resolution or 120 fps in resolutions higher than Full HD also isn’t an easy thing and here is no point in having a 240Hz LCD monitor if you cannot feed it with even 120 fps. And even at the moment top GPUs are having problems pushing constant fps of around 120 in more demanding games, so don’t be in a hurry with super big requirements for your next 3D monitor. Still in the next few years if the user interest in 3D technology keeps rising, there is much more content available and the prices continue to get more and more affordable thing might move in the right direction and DisplayPort can finally find the place it deserves, but we’ll have to wait and see…

If you remember the review of the 23″ Planar SA2311W 3D monitor I did not too long ago, you should also remember the interesting effect I’ve observed in the photo above (the banding on the white color). After testing a more recent model, namely the 27-inch Acer HN274H 3D monitor I have also observed the same strange effect with my extreme stereo 3D crosstalk test photos…

The photo above is of the monitor showing the 3D test photo and not through the lens of the shutter glasses, so don’t use it to judge for level of ghosting as it is not intended for that, but it is to investigate the strange gradation of white I’ve noticed. This test 3D photo uses black on white for the two eyes as this makes the strange color gradation of the white to be most apparent and it turns out that this issue is somewhat related to the OverDrive function as well as the current level of brightness (the contrast setting) of the monitor. If I disable the OverDrive through the system menu the problem with the gradation of the white disappears, but in turn I get a lot of crosstalk which is to be expected. If I push the contrast setting (the brightness) of the display higher or lower there is also difference in the banding of the white with the white turning out to be completely even after a specific value.

Of course the black on white stereo 3D crosstalk test photos are an extreme case that should not normally happen in real world use scenarios or it will be very hard to be seen with normal stereoscopic 3D content displayed on the screen. Nevertheless I wanted to know exactly what is causing this strange behavior, how exactly it is related to the use of OverDrive and why it was not present in the previous 3D-capable LCD monitors that I’ve tested already. So I’ve been in contact with Planar to get the answers to this questions and they were very helpful in explaining the exact reasons, also confirming my observations regarding the OD and contrast settings. I’m going to quote the exact response I’ve got from Planar below:

I’m going to try to explain why banding can be seen with certain stereo test patterns on Planar’s 3D Vision monitor. First, the goal of stereoscopic visualization is to show the left image only to the left eye and the right image only to the right eye. We want to prevent residual of the left image showing up when the right image is displayed, and visa-versa. Because lines addressed near the top of the display have more time to settle than lines at the bottom of the screen, the display electronics need to drive pixels more aggressively to switch from left to right as you get closer to the bottom of the screen. The display electronics has some limitations, where it can’t change the “aggressiveness” on a line by line basis. There are finite steps that the current drive electronics can control. This causes the banding, which can be seen on test images with constant gray values in one eye and high contrast in the other eye. However, as you stated in the article, this artifact is difficult to see in normal stereoscopic images because you would very rarely have large areas of a common gray level with high contrast between the left and right eye. If such an image were exhibited it would be uncomfortable to view (on any 3D monitor) because of the large discrepancy between the two eyes. This banding issue is below the threshold of visibility in real world images; just when guys like you or me test the extremes.

You asked why banding can be seen in test images on the new panel and not on the older ones. The older panels used one overdrive value for the entire display. This resulted in low stereo crosstalk in the middle of the display, but noticeable ghosting at the top and bottom of the screen. The new SA2311W monitor has low stereo crosstalk across the entire screen.

As for the reason that changing the contrast setting can eliminate banding, consider that with a low contrast setting you would drive a normal image from 0 to 85% (for instance) of the range available. This leaves some headroom for LCD overdrive which is used to improve 3D quality by reducing stereo crosstalk. In this case, you would see banding when a black image is shown in one eye and a high gray level (white) image is shown in the other. When you increase the contrast setting, you eliminate the headroom for overdrive. All the white values may be driven near 100% so that banding disappears, but then you observe ghosting. In general, a lower contrast setting results in better 3D quality for normal images.

The bottom line is that the appearance of this strange effect is a result from the efforts being applied in order to reduce the level of crosstalk/ghosting we are getting on the more recent 3D monitors and in order to have less ghosting at the top and bottom of the screen as compared to the earlier models. As it was already mentioned, this strange behavior is observed only with extreme test conditions and should not be easily noticeable in real world usage scenarios. And the white banding in these test photos will most likely be something that we are going to be seeing a lot from now on in the new 3D monitors that are about to come later this year, but you should not be worried about that fact. The important thing is that we are getting less and less crosstalk/ghosting with newer 3D-capable LCDs, right… ;)

During CES 2011 Acer and Lenovo have announced some new 3D-capable LCD monitors that are interesting for anyone that considers going for Nvidia’s 3D Vision solution for stereoscopic 3D gaming and 3D multimedia. Acer has announced the 27-inch Acer HN274H 3D monitor and the 24-inch Acer GN245HQ with both of them featuring both Dual-Link DVI support for frame sequential stereo 3D input that the 3D Vision uses as well as HDMI 1.4-capable input for stereo 3D content from consumer electronic devices. Both of these monitors also have built-in 3D Vision emitters, so you will not be required to have an external IR emitter anymore.

The 24-inch GN245HQ you see pictured above is pretty much following the futuristic design set by the first 3D-capable LCD monitor that the company has announced early last year. It offers up to 100 million:1 contrast ratio (dynamic and a rated as way too high to be actual value); Full HD (1920×1080) resolution; 23.6″ LED backlit panel with a 16:9 aspect ratio; a 120Hz refresh rate, essential for creating the 3D effect and a response time of just 2ms.

The bigger 27-inch Acer HN274H 3D monitor is actually the first one to probably hit the market with such big size and support for stereo 3D, especially since Asus has been postponing a lot the actual release of the 27-inch model they’ve been showing for quite some time now. The Acer HN274H 3D monitor apparently uses LED backlight and is with Full HD resolution, although still not a lot about its specifications are being publicly announced. If you are visiting CES you should be able to see it demonstrated at the Nvidia booth there, along with the other new 3D-capable products announced at CES like the other new Acer 3D monitor as well as the one coming from Lenovo. These two new 3D monitors from Acer should be available on the market in the next few months so the wait is almost over, especially for people waiting for a 27-inch model in order to jump into stereo 3D. And also in these new monitors having compatibility for use together with 3D-capable consumer electronics such as game consoles, Blu-ray players, set-top-boxes and others is a big plus, especially if you are not considering to buy a 3D HDTV yet. At CES this week, Acer is also launching the Aspire Z5763, one of the first 3D Vision-enabled all-in-one PCs featuring a 23-inch, full HD (1920 x 1080) 3D Vision display, NVIDIA GeForce GT440 or GeForce GT445M GPUs, a built-in 3D Vision emitter, advanced Dolby surround sound audio, a Blu-ray DVD drive, and optional TV tuner.

Now, regarding Lenovo. They’ve announced the new 23-inch Lenovo L2363d 3D monitor that has a quite interesting design, but apart from the monitor being a 3D Vision compatible one it also has another interesting 3D feature. I’m talking about the decision that Lenovo had for integrating a 3D-capable web camera inside the monitor (dual cameras) that can be used for taking stereo 3D pictures of yourself in front of the monitor or for making stereo 3D video conference calls with other people. And for everyone else there is the Minoru 3D camera available that can be used together with pretty much any monitor. Aside from the new 3D monitor, Lenovo has also announced the Lenovo IdeaCentre K330 3D gaming PC, but that is not as interesting as their new 3D-capable display. Still we’ll have to wait a bit more for more details and the full specifications to surface officially as well as information about pricing and availability for the display and the 3D PC.