Hands on: Powering up for HD

It doesn’t seem long ago that DVDs with bit rates above 6Mbit/sec posed a serious challenge for many PCs.

Today, the AVC and VC-1 formats commonly employed by high-definition titles on Blu-ray and HD-DVD are far more complex to decode, and typically delivered at much higher bit rates of 20Mbits/sec and above.

This month, we pushed a media PC to its limits and found the combination of a Core Duo mobile processor and even the best low-profile graphics cards could only just cope with modern titles such as Casino Royale on Blu-ray played at 1080p. This film typically employs bit rates between 20Mbit/sec and 30Mbit/sec and only occasionally peaks at 40Mbits/sec.

Other titles are already exceeding this: X Men III on Blu-ray regularly tops 40Mbits/sec and was beyond the capabilities of our media PC to play it smoothly at high resolutions. When building this system, we chose components that could squeeze into a slim case and run in virtual silence, but they were not powerful enough to decode the toughest high-definition titles at 1080p smoothly.

A boost in either the graphics or main processor performance should do the trick and we’ll test the theory by fitting the same graphics cards in a more powerful Core 2 Duo desktop system.

Measuring HD performance
Our test system employed an Intel Core 2 Duo E6700 running at 2.66GHz, fitted in an Asus P5W DH Deluxe motherboard with 2GB of Crucial DDR II memory. For graphics we used the two cards from this month’s Hardware column – the Sapphire X1600 Pro HDMI, which employs an ATI Radeon X1600 chipset, and the MSI NX7300GS-MD256EH, which uses an Nvidia Geforce 7300 GS chipset.

To measure the HD video performance, we used a Sony BWU-100A Blu-ray drive to play chapter two of Casino Royale and the opening sequence of X Men III. Since playback at 720p was possible with a less powerful configuration, we went for 1080p playback.

Our eyes are the best judge of smooth playback, but it’s also useful to measure how hard a PC is working at a particular time and to know what bit rate the video content is delivering at the same moment. To measure CPU load, we fired up Windows’ Task Manager, while PowerDVD Ultra’s ‘Show Information’ option revealed the current bit rates in real time.

With the Sapphire card fitted, Task Manager measured a CPU hit of 40 to 65 per cent during chapter two of Casino Royale; this compares favourably against the 75-90 per cent range during the same sequence with the slower Core Duo T2600 system. The more demanding X Men III regularly took the E6700 beyond 75 per cent usage, but unlike the T2600 system, it enabled smooth playback.

Switching to the MSI card saw a higher CPU hit of 48-70 per cent for Casino Royale – again comfortably below the high 80s measured under the Core Duo system for the same sequence. When fitted in the E6700 system, the MSI card had no problem delivering smooth playback of Casino Royale at 1080p, which is much more than can be said when it was coupled with the T2600. X Men III proved trickier, though. While the E6700 enabled the MSI card to deliver a far smoother presentation than it did with the T2600, it still wasn’t 100 per cent.

Out of curiosity, we also tried a full-size Gigabyte graphics card with an Nvidia Geforce 6600 chipset and, like the Sapphire card, this coped with both Blu-ray titles without any issues. This illustrates how a budget chipset such as the Geforce 7300 GS can be beaten by a higher-end chipset from an earlier generation.

All in the components
Our tests in this month’s Hardware and Performance columns illustrate that for smooth high-definition playback at demanding bit rates, you’ll need both a decent graphics card and a fast main processor. If one or both are compromised in performance to better suit the environment of a media PC, you may find your system struggling with the most demanding content.

At the time of writing, Nvidia announced its Geforce 8600 and 8500 series GPUs, which are the first to offload 100 per cent of the video demands of Blu-ray and HD-DVD from the main processor. This should enable smooth high-definition playback on systems with relatively modest main processors. Exactly what you can get away with remains to be seen, though.

Of course Geforce 8600 and 8500 series cards currently represent the pinnacle of graphics performance and hence carry high price tags and also require full-height cases. So, unless you’re either committed to a mobile processor or the best 3D gaming, it makes more sense to couple a slightly more modest card with a decent Core 2 Duo for an HD media PC.

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