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SD & HDTV decoding

We're stepping away from gaming for just one page. Ever since that past generation of graphics cards (Series 6), NVIDIA did something really intellectual. They made the GPU (the graphics chip) an important factor in en/decoding video signals. With a special software suite called PureVideo you can manage multiple processes in the GPU.

What are the key advantages of PureVideo? In my vision two key factors are a big advantage. To offload the CPU by allowing the GPU to take over a huge sum of the workload. HDTV decoding through, for example a TS (Transport Stream) file, can be extremely demanding for a CPU. These puppies can go to 20 Mbit/sec easily as HDTV streams offer high-resolution playback in 1280x720p or even 1920x1080p with the 7800 & 7900 cards.

By offloading that big task for the bigger part of the graphics core, you give the CPU way more headroom to do other stuff. The combination of these factors offer you stutter-free high quality and high resolution media playback. All standard HDTV resolutions of course are supported, among them the obvious 480p, 720p and 1080i modes (Progressive/Interlace).

Recently I built a Home Theater PC (read that article here) and by offloading the decoding process to the graphics processor an Athlon XP 2000+ processor was running at 40% CPU load while decoding a .ts High Definition 15 MBit/sec video stream. Just amazing!

Ever since the Series 75 ForceWare driver, PureVideo is doing something I've been waiting on for quite some time now, 2-2 pull down which converts 24 frames per second to 50 frame per second PAL.

I stated that for me personally there are two important factors, one offloading the CPU but do not forget another very important key factor, Image Quality. PureVideo can offer a large amount of options that'll increase the IQ of playback. This can be managed with a wide variety of options. Obviously NVIDIA has some interesting filters available in the PureVideo suite, we won't talk in depth on them but think of features like advanced de-interlacing, which can greatly improve image quality while playing back that DVD, MPEG2 or TS file (just some examples). Aside from that, things like color corrections should not be forgotten. All major media streams will be supported by NVIDIA with PureVideo. Small sidenote, High Definition H.264 acceleration, which will become a big, new and preferred standard, is also supported.

Please bear in mind: the following is not 100% PureVideo related, as playback and connectivity work straight out off the box: You do not need PureVideo for HDTV playback and connectivity, but it is recommended.

We put this to the test on a Pioneer Plasma screen. First off some tips. Whether you like to hear this or not if you want to connect your PC to the HDTV screen use the best and thus most expensive connection available. You can go with a component adapter and the 3-way RCA cable. However, and as weird as this might sound, image quality while being good is simply not perfect, it's still analog you know. It's a cheap way to connect to a HDTV screen though. Now what you want to do is to go digital on the connection. Obviously you spent a lot of money on the HDTV screen and PC, so invest a little more into a digital solution. You'll notice that your card has a lovely DVI-I/D compatible output, so please use it! Buy the expensive Digital DVI cable and connect it to the Plasma with the best connector available on your TV, either DVI or HDMI. In our case, I used a DVI-D <-> HDMI cable. Once you boot up into Windows you'll immediately notice the difference; rich colors and good quality.

Once booted into Windows you'll likely notice some seriously bad overscan (the Pioneer screens are known and feared for this). Basically the outer segments of the screen are not being displayed on your HDTV. NVIDIA is now offering some really cool under and overscan options. In essence you shrink the resolution a little to make it fit perfectly on your HDTV. I believe this is being done by adding black borders to the video signal. The new ForceWare 75 series actually allow independent X and Y underscan control in a very simple manner. Doesn't matter because after you've done that the only thing you can say while playing back an HDTV file is "Oh my God." The image quality is simply beautiful and seems to work extremely well with NVIDIA's recent graphics cards.

Here in Europe HDTV is still not a big thing and that is so very, very terrible! But we are slowly (very slowly) getting there. The first HDTV networks have started broadcasting on Satellite like our European HD1 and even the feared by reputation Canal+ France is working on an HDTV movie channel. The underclassed and underprivileged among us simply have to be, shall we say, a little creative to find HDTV files. As stated, this little bit above is not exactly PureVideo related though, but hey the two merge together. We want to tell it all so you know what to expect.  PureVideo itself then. Really it's not 100% needed, yet it's advised to use it. It en/decodes your media streams with the best possible filters as a symbiosis with the GeForce graphics cards. You can easily divert PureVideo by buying separate codecs or DVD playback software like the lovely Theatertek playback suite though. HDTV playback whether it was with a DVD or .TS file was looking shockingly good. Image quality is rich and sharp and the new de-interlace filters obviously do a fantastic job. Much better compared to the standard decoders I have seen. You can actually monitor and set a wide variety of settings real-time as in your tray bar a new icon will appear.

Click the purevideo icon and you'll get the PureVideo options.

We also tested if the CPU indeed was offloaded by the GPU to see if the PureVideo claims are true. Well, they are. With the same HD movie we logged CPU utilization during playback.

.TS files to me personally are important, if your satellite box can record an MPEG stream it'll do that in a .TS file. In our case we had a .TS episode recording of the Sopranos. This puppy is doing a 12 to 20 mbit/sec datastream which is one of the most difficult things to manage for a PC right now (if you do not have the proper decoders). At standard even our AMD Athlon 64 4000+ was managing to peak out at 55-60% CPU utilization. Once you offload it to the graphics processor things look much better with the help of PureVideo. Have a look at the graph below where you are monitoring the CPU at work at roughly 12-20% decoding a HDTV .TS file:

Indeed, a huge improvement over standard decoding. We are now at a CPU utilization of 12-20%, really nice. The processor is almost doing nothing. Let me remind you again that this is a Transport Stream file with a HDTV resolution of 1920x1080i (and yes it's big, 6 GB for 50 minutes).

In combo with the new drivers you can now also decode High Definition H.264 streams. H.264 is a compression algorithm used to transmit video efficiently between endpoints. This algorithm is seen as the replacement for its predecessor, H.263. What is different about H.264 is that it promises to deliver high quality video, H.264 also enables very high quality encoding, producing better results than even MPEG2 and of course HDTV levels.

These 7600, 7800 & 7900 cards can also manage 3:2 and 2:2 pull down (inverse telecine) of SD and HD interlaced content. Software like WinDVD, PowerDVD and Nero showtime will start to support PureVideo from within their software. You can also buy the PureVideo codec at NVIDIA after which MediaPlayer or Media Center will work with is flawlessly.