For anyone looking into setting up a Home Theater PC (HTPC), the choices for TV tuners are quite vast. Pretty much all people would need is something that can display and record TV shows, though an added bonus would be Microsoft Media Center support. Image quality should be good, and a remote is always nice to have.

Over a year ago, we looked at a couple products based on ATI's Theater 550 Pro. It was a very good TV tuner product, but given how much TV has changed in a short 18 months, it was about time for something of an overhaul. While not completely new, the ATI Theater 650 we'll be covering today does build on what made the Theater 550 Pro popular, as well as adding some new features not seen before on a standard TV tuner.

ATI Theater 650

It's pretty rare that we comment a whole lot about box art, but ATI has taken an initiative to simplify the decision process for potential buyers. While we would imagine most of our readers typically do a lot of research prior to purchasing, not everyone does. Therefore, key features are bullet pointed on the front of the box, though the product is capable of much more than what is stated.

The Theater 650 should have no problem fitting in most ATX cases due to its small size. TV Tuners aren't nearly as big and complex as most video cards, and everything you need to power a HTPC is packed into a rather small PCI card. Those of you thinking of an upgrade from the 550 Pro should know that the Theater 650 is about a half inch longer. The Theater 650 does support PCI Express x1, but for now you can expect all cards to be built on the PCI interface.

Other than the card, ATI tosses in the required cables, including a 7' FM radio antenna, and an AV In breakout box. The box is for input only, and supports S-Video, composite video and composite L/R audio. There was no remote with our package, but ATI does offer a free Remote Wonder Plus (instructions on how to receive the remote is on the installation CD).

There are several items on the PCB that make up the Theater 650 product. To keep video running smoothly, 128MB of ram is packed into the ATI Theater 650, and assists in the buffering of the video. This should make the video more responsive (faster) as it can cache some of the video information rather than passing all of it through the PCI bus. The ram itself is Samsung's K4D551638H-LC40 memory, which is rated at 250MHz and is exactly the speed ATI runs the ram at.

There is a ATI designed, but Samsung built mini-can tuner that supports both analog and digital signals. The idea behind the mini-can tuner is it takes up much less PCB real estate than older analog tuners, but is more responsive than silicon tuners. As you may have guessed, the Theater 650 does indeed support high definition signals, albeit over the air signals.

The Theater 650 chip is the real star of the show though. ATI has squeezed an audio/video decoder, MPEG-2, WMV9 and H.264 encoder. Digital rights management does rear its head here with a hardware DRM engine. The chip features a 12-bit video decoder, which offers more precise video capture and outputs more realistic colours.

The Theater 650 supports a 3D motion adaptive comb filter, which supports both Sequential Color with Memory (SECAM), NTSC and PAL standards. The 3D comb filter is used on low motion scenes. Examples of these are still pictures, slow moving video or static items like the broadcaster's logo.

No comb filter	Theater 650 3D Comb Filter

Usually the 2D filter was used to separate the luminance and chrominance components of the TV signal. This can cause color artifacts around the edges or a dot-crawl effect. The 3D filter analyzes 5 lines of video in the current frame, and also scans ahead 1 frame to analyze the video to see if the picture changes.

A 5-line 2D comb filter is used on the high motion video feeds. A 5-line filter ensures that every pixel is separated with a high degree of accuracy. By reading ahead 5-lines before the video is processed, the comb filter can detect similarities in the lines and determine how to separate the signal in the most efficient manner. Another image quality enhancement is noise reduction. Noise or snow can be seen in lower quality signals, or video streams. The Theater 650 contains advanced dedicated algorithms which search for a variety of noise in the signal and cancels it out. This is also done on-chip, to reduce CPU utilization.

Automatic gain control is a system in which the video stream is smoothed of any major fluctuations in signal strength or in brightness or intensity of the light displayed. These differences are often evident on channel changes, where the screen will become extremely bright. The Theater 550 Pro used a single staged gain control, but the 650 Pro uses a multistage and multispeed control.

The Personal Video Recorder feature is something I'm sure many of you are aware of. The Theater 650 will allow you to watch and pause live TV as well as recording your shows for later viewing. The only additional upgrade you may want to consider now is a bigger hard drive though as mentioned earlier, Free-to-Air HDTV is possible with the Theater 650.

Moving from left to right, your input and output options are as follows: Cable TV In (COAX), the FM Radio or DTV connection, and the AV In connector for the breakout box we've covered earlier. Overall, the ATI Theater 650 supports 3 AV In options. These connections are not just for TV though as you can plug in a variety of devices such as camcorders, DVD players or other video devices that use the above connections. While Free-to-Air HDTV is possible, cable and satellite HDTV is not, hence no HDMI or even DVI will be found here.

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