Getting Dirtier: Graphics

With the majority of the under the hood work focusing on graphics, there’s a lot to cover, so let’s get started.

Although it is being released for Vista too, Windows 7 marks the official introduction of Direct3D 11. As a superset of Direct3D 10.1, Direct3D 11 adds support for tessellation, multi-threaded rendering, and GPGPU abilities via the Compute Shader. We’ve already covered a great deal on Direct3D 11, so please see our introduction article on it for more details.

Next up we have the Windows Display Driver Model 1.1, which in turn is the lynchpin for several other graphics related features. WDDM 1.1 itself is not particularly impressive, but it’s what it allows that is. For all practical purposes, all we need to know about WDDM 1.1 is that it’s a minor revision of WDDM that requires DX10-class hardware (rather than DX9-class on WDDM 1.0) and as such allows the operating system additional features.

So what can you do with WDDM 1.1? For starters, you can significantly curtail memory usage for the Desktop Window Manager when it’s enabled for Aero. With the DWM enabled, every window is an uncompressed texture in order for it to be processed by the video card. The problem with this is that when it comes to windows drawn with Microsoft’s older GDI/GDI+ technology, the DWM needs two copies of the data – one on the video card for rendering purposes, and another copy in main memory for the DWM to work on. Because these textures are uncompressed, the amount of memory a single window takes is the product of its size, specifically: Width X Height x 4 bytes of color information.

Image courtesy Microsoft

Furthermore while a single window may not be too bad, additional windows compound this problem. In this case Microsoft lists the memory consumption of 15 1600x1200 windows at 109MB. This isn’t a problem for the video card, which has plenty of memory dedicated for the task, but for system memory it’s another issue since it’s eating into memory that could be used for something else. With WDDM 1.1, Microsoft has been able remove the copy of the texture from system memory and operate solely on the contents in video memory. As a result the memory consumption of Windows is immediately reduced, potentially by hundreds of megabytes.

What makes this even more interesting is how this was accomplished. With WinXP, GDI+ was partially accelerated, but this ability was lost to little fanfare when the DWM was introduced for Vista and thereby made GDI+ acceleration impossible, pushing all GDI work back to the CPU. This in turn is responsible for the need for a local copy of GDI and GDI+ windows and the increased memory usage of Vista, as reading data back from the video memory for the CPU to work on is too slow to be practical. The solution as it turns out is that by reintroducing GDI acceleration, the amount of read-backs can be minimized to the point that a local copy of the texture is no longer necessary. Now GDI isn’t completely accelerated, only the most common calls are, but this is enough that when the least common calls trigger a read-back, the performance hit is negligible.

This is one of the bigger changes in Windows to get memory consumption under control. The problem was particularly bad on netbooks and other systems with integrated graphics, as the video memory is the system memory, resulting in two copies of the texture being in the system memory (something such a machine probably has little of in the first place). The fact that this requires a DX10-class card with a WDDM 1.1 driver needs to be reinforced however – this won’t be of any help for systems with lesser GPUs, such as Atoms paired with the 945G chipset, as the GMA 950 GPU on that chipset is only DX9-class. NVIDIA, no doubt, is grinning from ear to ear on this one.

The other big trick as a result of WDDM 1.1 is that support for heterogeneous display drivers has returned. With WDDM 1.0 and its homogenous driver requirement, computers were limited to using video cards that would work with a single driver – in turn limiting a computer to video cards from a single vendor. With heterogeneous driver support, computers are once again free to use non-matching video cards, so long as they have a WDDM 1.1 driver. Besides that, this also is a boon for GPGPU use, as GPUs continue to interface with Windows via WDDM regardless of whether they’re actually displaying something or not. For example, this would allow NVIDIA to sell video cards as GPGPU processors to ATI owners, and vice versa.

WDDM 1.1 also brings a few lesser features to Windows 7. The DWM can now run in DX10 mode and new controls are introduced for aspect ratio scaling and controlling monitor modes.

Moving on from WDDM 1.1, Microsoft has also introduced some changes to GDI that do not require new display drivers. Along with requiring a local copy of window textures, the GDI stack was locked so that only a single GDI application could access it at a time. The GDI stack has been rebuilt so that the lock is more or less removed. Multiple GDI applications can now issue commands to it at the same time, and this is all pushed off to the video card to be its problem.

Images courtesy Microsoft

Unfortunately Microsoft has not provided us with any examples of this in action, so we’re not sure just what the real-world benefit is.

Next up, more DRM. Although we’re not entirely sure what has been changed, Microsoft has told us that they have made some changes with respect to DRM and GPU acceleration. Previously some applications playing DRMed content needed to switch to overlay mode to ensure the content was protected the entire way through. Likely this is a new low-level API for such functionality; Microsoft’s notes mention a standardized API for CPU to GPU encryption.

Last but not least, we have two new high-level graphics APIs in Windows 7. The first is Direct2D, the successor to GDI and a replacement for some Direct3D functionality. Like Direct3D, Direct2D is a fully hardware accelerated API, but it’s only for 2D operations. When Microsoft deprecated DirectDraw, the intention was for developers to use Direct3D for all of their 2D needs, but this never quite worked out as well as they intended. So now we have Direct2D, which gives developers a dedicated 2D API once again, along with a clear replacement for GDI.

Also introduced is an API specifically for text, DirectWrite. Where Direct2D works on 2D primitives, DirectWrite is responsible for the hardware anti-aliasing of text. NVIDIA sent us some documentation on the matter, and apparently the anti-aliasing method used (YDirection Antialiasing) can provide even better smoothing than ClearType can alone. It does not sound like any Windows components are currently using DirectWrite however.

Hardware font anti-aliasing in action. Image courtesy NVIDIA

We should note that while the “Direct” name implies these APIs are a part of DirectX, all of the material we have on the matter only mentions Windows 7. They may not be part of DirectX, in which case they would not be added to Vista as part of DirectX 11.

Getting Dirty: What’s Changing Under the Hood Windows Media : New Codecs, New Looks, New Features
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  • izal169 - Thursday, July 2, 2009 - link

    development of the technology is quite rapid. My computer specifications are not strong for Windows 7 that high quality. specification of my computer, intel core 2 duo, 1 Gb RAM, VGA Nvidia 7300 GS. microsoft is very cool. can make the OS with a relatively quick time.">
  • deteugma - Friday, June 5, 2009 - link

    I was an XP diehard until I installed Windows 7. Now I'm a convert and a proselytizer. I love Windows 7. It will be the first version Windows that I actually buy for myself, rather than accept for free from a family member's employer (university license). MS won't have trouble winning converts from the diehard crowd.
  • Biomorphic - Wednesday, May 27, 2009 - link

    Windows 7 has software based audio processing just like Windows Vista and my question is, will VXP enable hardware based audio processing or will it remain software based?
  • PC Reviewer - Monday, May 18, 2009 - link

    it looks alright as long as its performance is as good as, if not better than xp's. Im looking to do a review about Windows 7 on my blog soon aswell.">
  • alon - Sunday, May 17, 2009 - link

    First, I did not read all the comments, so if this has already been stated, I do apologize. For that matter, after the "Standard Test Bed" page I stopped reading the article. So .. maybe these issues have already been discussed.

    1) OK, so Vista x64 SP2 was released around May 11th (at least for my MSDN subscription, possibly earlier for others?) And it appears that the Windows 2008 SP2 bits were released around May
    14th. I still don't see an SP2 installer, but I can do a clean install with SP2 already slipstreamed. So ... I've looked and looked, but I can not find an XP Pro x64 SP3 anywhere. And according to Microsoft around last September, there was not going to be an WinXP Pro x64 SP3. So ... if you do have this SP3 around ... please let me know what MSDN/TechNet or whatever subscription you have so I can upgrade mine ... or point me to the release page.
    2) Concerning corporate IT ... one of the issues mentioned at the beginning of the article is the computing resources needed to run Vista ... which to me alludes to the fact that many companies chose not to upgrade to Vista based on HW requirements (of course Vista without Aero can run on many "lower" configurations, but of course the average company employee does not know this). I digress ... your test bed platform is not really anything that CorporateIT depts will be deploying. Core i7 ... released 7 months ago ... 6GB RAM. Please ... if you are going to try and "proove" that performance is decent with Windows 7 ... at least run some test systems that are not the toys we dream of, but the systems that are installed in the office. Until Microsoft and folks like you understand that companies can not afford to always buy new HW, the new OSs have to run on the last generation technology (actually more like HW from 2 years ago) ... your comparisons and results are useless ... and my 18month old Lenovo T61 does exactly what I need it to do. So, there would be no reason to upgrade to Win7 until MS End-of-lifes WinXP.
  • Razer2911 - Wednesday, May 13, 2009 - link

    Moving on from Vista 32, I have to say i'm impressed. There are very subtle changes and tweaks which actually make the experience better. A simple example would be the new taskbar, Jump lists and Aero peek feature. I for one dont like a million windows open on my desktop, somehow i always found it cumbersome and cluttered but within a couple of hours of using Windows 7 i found myself using 10-15 windows without getting bothered by the clutter. Never used a Mac but these new features actually have both form and function.
    One thing that i have not been able to figure out as yet is that all my videos (divx) and movies look very grainy and slightly pixelated on WMP 12 and VLC.
  • tomb18 - Tuesday, May 12, 2009 - link

    Support for canadian television in canada has always been limited in Media Center. Since HD digital over the air broadcasts (atsc)became available in the US, this has been supported in Media Center but not if you lived in Canada. Digital tuners are DISABLED by media center in all versions including Windows 7. This is in spite of the fact that canada uses the same ATSC system as the US. Many hacks have appeared but they always seem to be disabled by updates. This continues in Windows 7. As soon as the software determines that you reside in Canada, it disables the ATSC tuner.

    But get this. South Korea uses the same ATSC standard and it IS supported in that country.

    There are a lot of forums (such as the green button, run by the media center developers)that discuss this to no avail. No amount of questions, emails, or anything will get a comment from Microsoft. Even when MSVP's try to take up the battle nothing gives.

    There has been a lot of hope for Windows 7, that it would finally be supported, but alas, it is the status quo. My question is will Microsoft give a warning about the version of Windows 7 that contain media center for the canadian market telling canadians that their digital tuners will not work?

    I really wish that some website with industry influence (hint...hint) would expose this pointing out to the canadian market that they should not buy Windows 7 if they want to use the media center.
  • AnnihilatorX - Tuesday, May 12, 2009 - link

    Replace the function of minimising other windows with one that makes the window being shaked always on top. Now this is a useful function.

    Nevertheless I have been using AutoHotkey (automation programming platform) to assign Alt+z hotkey to make windows always on top in other windows. This is a feature I can't live without, along with Windows key + Scroll wheel on mouse to change transparency. These had help me multitask with different windows very efficiently.
  • rasmasyean - Sunday, May 10, 2009 - link

    I think people might have over-estimated Vista as the OS that will sweep across the world and change computers as we know it over-night. It didn't exactly turn out as expected, but I don't think it doesn't seem it did too bad.

    Gartner research report predicted that Vista business adoption in 2008 will actually beat that of XP during the same time frame (21.3% vs. 16.9%)[80] while IDC had indicated that the launch of Windows Server 2008 served as a catalyst for the stronger adoption rates.[81][82] As of January 2009, Forrester Research had indicated that almost one third of North American and European corporations have started deploying Vista.[83]">
  • compuser2010 - Sunday, May 10, 2009 - link

    "Never underestimate the power of marketing – many people can tell you they don’t like Vista, few can tell you why."

    I don't like Vista primarily because of built-in Digital Rights Management (DRM). Any time I need to capture, edit and/or transcode audio and/or video, I need to go back to XP.

    I have confirmed this with the following programs:

    Audacity 1.2.6
    Canopus EDIUS Broadcast 4.61
    Creative Labs Smart Recorder 2.40.23
    Moyea FLV to Video Converter Pro 2
    Ulead DVD Workshop 2

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