HDTV

These days you see computer stores selling more home electronics, and electronic stores selling more computers. Apple has made billions showing us that music and computers go hand in hand. Convergence was the hottest word a few years ago, but then companies realized that they needed more than simple marketing to put it all together. Today, we’ll put together a High-Definition Home Theater PC. This is one area where a custom designed computer makes the most sense since you will need to bring together the best of all technologies. First we need to define what a home theater PC needs to be.

In contrast to the other computer systems, a home theater PC must be able to integrate in a modern home entertainment center. At a minimum, this should include an HDTV and a digital surround sound system. To interface with these technologies, the PC will need to output an HD compatible signal for the video and a digital audio signal to your audio processor, so we’ll start with our methods for accomplishing this.

GPU

Whereas the fundamental component of the desktop and workstation was determing the platform, for a HTPC, the video card is what’s critical. The most expensive video card may not be the best choice for a home theater PC. If you have an HDTV with HDMI or DVI inputs, then you need to have DVI outputs on your video card -- that makes sense. Some of the older HDTV displays may not have a DVI input, or may not have enough digital inputs. This is when you need a card that will output to component video in a HD compatible format. Going beyond that, you need a video card that will allow custom resolutions. To determine if your video card will do these deeds, check this list for ATI (http://www.ati.com/products/hdtvadapter/faq.html#2). Among the NVIDIA cards, only the 6600 line seems to ship with component video out adapters – the other GeForce 6 series cards only work with HDTV over DVI. The 7800GTX also has component video out.

Our choice for this assignment is the GeForce 7800 GTX. On the surface, you’d think we chose it because it’s the newest card but in fact we’ve gone with the 7800GTX over any other GPU, not because of bragging rights or even its ability for hardware acceleration of MPEG-2, but because we’re looking for the best hardware PC solution for de-interlacing: PureVideo.

What’s PureVideo?

PureVideo is NVIDIA’s marketing term for the video processing found in NVIDIA GPUs, so it means a lot of things. You actually need both a NVIDIA GPU and the NVIDIA DVD Decoder (also called NVIDIA PureVideo Decoder) which costs about $20. The NVIDIA “DVD” decoder is in fact a full MPEG-2 decoder and can deal with 720p and 1080i MPEG-2 Transport Stream demuxing and decoding. Only with the NVIDIA’s software can you take full advantage of the video features of the NVIDIA GPU.

Most people look at video performance on the PC as being hardware acceleration of the MPEG-2 or H.264 decoding process as the big deal and hardware de-interlacing as the other feature on the checklist. In fact, de-interlacing is actually far more important. You can always throw a faster CPU at the decoding process. A Pentium 4 3.6GHz will decode H.264 in software just fine (with 95% CPU utilization) and so any dual-core CPU will have no trouble giving up one of its cores.
The quality of your de-interlacing is what will affect your picture quality the most. More importantly, you can’t simply throw hardware at the problem. More megahertz doesn’t actually do anything – you have figure out what your algorithms are going to be, and the best image quality comes from the most elegant algorithms.