Video Quality and Performance

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Hopefully this is the last time I'll talk about a video product in subjective terms. In the future, we're aiming to provide you with our test video sequences, reference frames and testing methods (or at least most of them) so you can analyse the video in the same way I will, to help you make up your own mind about quality. I'll obviously also offer up my own opinion on what I see, but you'll be able to analyse specific video data yourself to vindicate or rubbish what I'm describing.

Compressed video quality and performance

ATI's MultiMedia Center software offers up four different options for outputting AV streams to your hard disk, when recording using the PVR functionality. ATI's own VCR format is basically a wrapper around MPEG-2 AV, to further enhance its ability in terms of large files. You can transcode back to MPEG-2 easily using the VCR format. You've then got a choice of MPEG-2, spat out directly by the 200's compression engine, followed by transcode options into MPEG-4, AVI and WMV (using the WMV9 or WMV9 encode engines). Using the Library application, you can also transcode to MPEG-4 using the AIW and MMC9.03 if you've previously recorded in a seperate format.

In terms of quality, you can record PAL video in each of the offered formats with the MPEG-2 datastream option maxing out at 8Mbit/sec for the maximum 720x480 video resolution.

Subjective quality was tested using two maximum bitrate MPEG-2 streams, one low-motion, one high-motion, compared to the same test video played back through an ATI Theater 550 PRO PCI tuner and also captured to MPEG-2. At maximum bitrates for each but scaled output (I 'drop' around 10% of the scanlines in the scaler), there's little to choose between the two output engines (we're comparing Theater 200 to Theater 550 PRO in their native MPEG-2 output formats here) when I feed them PAL DVD video streams via the S-Video connector (the highest quality option with X800 XT AIW, requiring no chroma/luma split). This test basically does passthrough of the video stream, after cleanup and scaling.

The Theater 550 PRO offers better output quality for the low-motion video, due to its more advanced comb filter (per-pixel 3D comb). With the high-motion video there's similar levels of aliasing and artifacting with both, indicating the 550 PRO is selecting 2D comb for most of the frame. In this respect, although subjective, the 200 does well against its newer and technically advanced sibling.

Testing with TV was done by splitting an input feed into two (using one splitter/amp) and recording simultaneously using the X800 XT AIW and Theater 550 PRO in the same system. Recording the output streams was done to separate hard disks for each tuner. The test video stream was a 5 minute section of the recent Australian Formula 1 Grand Prix, right before Schumacher gets nailed and pushed out of the gravel trap by the brave marshalls.

It's a decent test since it's a high-motion section followed by snippets of low-motion slowed down video as the director focusses on Schumacher's mistake. Tuning TV, the 550 PRO offering better quality throughout, especially in terms of colour reproduction based on what I can see on my own television after recording similar video using a DVD recorder. In terms of aliasing and cleaning up the feed, the 200 does well against the 550 PRO but ultimately can't compete overall. That's not to say the 200 is bad hardware, far from it, it's just less able than 550 PRO.

In terms of CPU load, there's less than 30% actual CPU load (not the same CPU load metric as reported by Task Manager, for those interested) at all times from both bits of hardware running at the same time. They don't need the CPU very much at all.

Live tuned TV and live S-Video feeds on the desktop

This is a test I'm particularly interested in personally, since my main usage from a TV tuner on the PC is to watch video in a window, scaled usually, rather than output to disk as a PVR for watching later or using it as a replacement for my TV's in-built tuner. I also like to feed in S-Video or composite from various sources, sometimes interactively as I play a game on a console, into a scaled window on the desktop.

I tend not to care about large 10-foot GUIs when watching TV on a PC, or how I can stream the video round my house or what capture quality I can get. I just want to watch a scaled video feed in a window, while I work.

Click for a larger version
In this respect, the X800 XT AIW offered up a problem I've not seen elsewhere and which I couldn't remedy. As you can see from the photograph above, live TV looks pretty good and I have no issue with the AIW's ability in this area. It's the same great TV quality ATI have been giving me in their products for years now.

However, if I feed in composite video via the breakout box and display it using MMC, it's not interactive. That is, if I'm feeding in from my PS2, when I control the action on the screen using the controller, there's a couple of seconds of lag before it happens on screen in the scaled window.

Otherwise, my experience with the X800 XT AIW in terms of video performance and quality was great and as expected. ATI aren't breaking the mould too much with this last AGP All-In-Wonder and that's a good thing, finishing off an era of AGP AIWs in style.

[Pages]
   Last Page
   [1]· Introduction
   [2]· The Video Pipeline for All-In-Wonder, from TV to TV
   [3]· ATI's Radeon X800 XT All-In-Wonder
   [4]· Video Quality and Performance
   [5]· System Setup and Notes
   [6]· 3D Performance
   [7]· Thoughts
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