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DisplayPort – the Future of 3D-capable Computer Monitors, or Not

October 3rd, 2011 · 9 Comments · Other S3D Tech

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…

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9 responses so far ↓

  • 1 Gerard // Oct 4, 2011 at 07:57

    Now you are talking my language. I am happy with an older Quadro FX card solution running the Acer 27″. Full resolution/frequency per eye for a great quad buffered stereo experience…. funny, I haven’t tried any games with it yet…. hmmm….
    Back in the day, before 3D Vision software, I woud run stereo at 1280×1024 100hz. The best CRT I could find could do 144Hz, but only at a resolution of 1024×768.

    There will always be a trade off, no matter what the hardware is… > frequency = < resolution

  • 2 blackrat // Oct 4, 2011 at 10:55

    I have only to mention to the last sentences of the blog, the difference between refresh rate of monitor and fps of graphics card: A constant fps of 25-30 should be sufficient, but this must be rendered for both eyes (for both eyes acutally 50-60 frames/s).

    BTW, my personal bet is autostereoscopic parallax barrier with eye tracking! I’m eager waiting for this displays in 24″ or 27″.

  • 3 miahallen // Oct 4, 2011 at 11:16

    I’m perfectly happy with current technology (less ghosting would be nice), but why can’t the TV’s keep up with the computer monitors? Why can’t I get a 46″ TV to replace my computer monitor that will support 3D Vision? Doesn’t make sense to me :-(

  • 4 CrystalCowboy // Oct 4, 2011 at 19:49

    I have been waiting hard for this, and I guess I’ll have to wait some more. Some technologies take off immediately (PCI-express comes to mind) but it is frustrating that others, like DisplayPort, take so long.

  • 5 Zerofool // Oct 8, 2011 at 15:50

    “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. ”

    This is not entirely correct. The HDMI standard (since v1.3) defines bandwidth which is more than enough for 1080p @60Hz per eye. All High Speed HDMI 1.3 cables are capable of this. So where’s problem? The problem is in the lack of transmitter chips, capable of the full 340MHz specified in the standard. In an interview for MTBS3D from few moths ago, HDMI officials confirmed that chips capable of 300MHz (and 1080p@60fps 3D) are currently in development by Silicon Image, and should appear by the end of the year. These chips will finally (physically) allow for 1080p @60Hz per eye gaming. So don’t be surprised if next year we see HDMI 1.4b or 1.5 revision – still using the same cables and specifications, just added this new mode, and requiring the new chip, and a new license of course ;). That’s why I hate HDMI – they are blood sucking leeches, doing everything possible to get more money. That’s why I hope they crash and burn, and DisplayPort becomes the industry-wide standard.
    Anyway, I doubt that 2012 lines of 3DTVs will support this new HDMI version (or DisplayPort), so we’ll have to wait even more. :(

  • 6 Graeme // Oct 11, 2011 at 13:43

    As long as you get 120Hz per eye, I don’t mind if I will only be getting 60fps in the actual game as at least the image will be smooth with no flicker and a reduced input delay.

  • 7 LiteSoul // Oct 12, 2011 at 00:32

    There is one other thing coming that needs to be taken into consideration:
    The Hobbit
    It’s being filmed in 3D at 48fps (each eye) because Peter Jackson tested it (suggested by pioneer James Cameron) and it solves ghosting, headaches, etc, while at the same time enhancing clarity in film.

    So there will be films coming filmed at 48fps

  • 8 Emearg // Dec 30, 2011 at 00:28

    @Graeme – to get 120Hz per eye, the game needs to be running at an astronomical 240fps.

    If the game (limited by your hardware) is running at 60fps overall, you’re going to see 30Hz in each eye when you go 3D.

  • 9 Specfreq // Feb 15, 2012 at 01:46

    Good read,
    the requirements for rendered content and displaying 120hz per eye is quite staggering. Even still, people are going to want it if it says true 240hz on the box.

    If it were possible to make a panel that wan’t affected by ghosting at 240hz, would it make any difference for 3D content? I would think so, but there’s likely to be a huge trade off somewhere along the line.

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