Playing HD Content on AMD-based Machines

We've analyzed video playback in modern high-quality resource-intensive formats several times already. Unfortunately, it's usually difficult to apply test results to your own computer, because there's multitude of HD video formats and we might just miss the formats you are interested in.

So we decided to conduct several additional tests in order to evaluate real hardware requirements for playing HD video on modern media, such as Blu-ray and HD DVD. These tests, in our opinion, may be interesting and useful to those building rigs with extra capacity for the future needs.

First of all, let's briefly outline the formats to be used in this article. As is well known, the usual resolution of Blu-ray and HD DVD video is 1920x1080 (to be more exact, we have seen only such editions, except for bonus tracks in the standard resolution). Video may be interlaced or progressive; 24, 25 or 30 frames per second (the standard also includes other options). Video can be compressed with MPEG2, H.264/AVC, and VC-1 codecs. While the first of them is a very easy task for most modern computers, the others can pin down quite powerful PCs. In order to avoid it, GPU manufacturers have been using special units to offload a CPU when decoding "heavy" formats.

We shall not analyze audio, which also requires decoding. We can only note that Blu-ray and HD DVD can use new audio formats, such as Dolby Digital Plus and DTS HD. But judging by how easily AC3 is decoded, the new formats will probably not be much harder to decode. The software player in our tests decoded audio to speakers via the analog interface, as the most resource-intensive option. Another option - transferring audio via the digital interface to an external receiver (which supports modern formats) - can theoretically reduce the load on a CPU. We compared digital output with the CPU-decoded option. The difference in the Dolby Digital format was about 1% (with Athlon X2 64 5000+).

It's impossible to watch video without a special software player and/or decoders. Unfortunately, there are very few programs that can use graphics cards to decode video. We can even say that there are only two of them - Cyberlink PowerDVD and Intervideo WinDVD (the latest versions of Nero ShowTime can also do it, according to its developers). Besides, don't forget that new discs have a new protection system, which also limits the choice of players. So we've got these two players. Bottom line - you have to use a special software player to play optical discs of the new formats. If you want to watch you own video files created with AVCHD or a HDV camera (not protected), you can use the above-mentioned cameras as well as any other programs, because the former let the operating system use their decoders. Besides, you can use other decoders that support these formats, for example CoreAVC.

The programs have another limitation - you can play HD discs only through the digital interface with a monitor/TV-set with HDCP support. It means that a graphics card and a display must support Digital Content Protection. If they don't (for example, in case of the DVI connection), the player will refuse to play video. However, there is one trick - protection is required from a digital connection. It means that you can watch protected HD video through an analog connection, such as VGA or component. Resolution will be really high only if a disc does not have a special flag that prohibits full resolution output through analog interfaces. Fortunately, no such discs have been manufactured so far.

HDCP is sometimes associated with HDMI connectors. That's not correct. It's just HDMI (which is actually DVI plus S/PDIF) usually supports it, while DVI doesn't. We've been hearing about HDCP support in graphics cards for a long time already, but even now this feature is sometimes optional. So if you plan on using a graphics card for HD playback, you should make sure your model supports HDCP. What concerns displays, two-year-old TV-sets can already have a DVI connector with HDCP support. The situation with monitors is more complex, but many modern large models have this feature.

We should also mention resolutions supported by HDCP receivers. There are only three scan options - 1280x720 (720p) and progressive and interlaced 1920x1080 (1080p and 1080i correspondingly). As most inexpensive panels have the physical resolution of 1366x768, you'd better use 720p mode with them. High-resolution computer monitors use the 1920x1200 mode. Unfortunately, a Full HD panel cannot guarantee the lack of black stripes on your display - some HD discs have the 2.40:1 format, which differs much from the 16:9 TV format (1.78:1), to say nothing about 16:10 monitors (1.6:1). Movie industry seems to live its own life and does not pay attention to technical resources of most users. This issue formally affects complexity of video decoding.

We ran our tests on a computer with the Biostar TF7050-M2 motherboard on the NVIDIA 7050 chipset. AMD Athlon 64 X2 5000+ processor (2.6 GHz, 512 KBx2 L2 cache) can be easily downgraded to other models with OS tools to lock cores and RMClock to reduce clock rates. So we can determine minimal requirements for HD video playback.

The diagrams will show clock rates and a number of cores. You can use our table to convert these data into model numbers (AM2 processors). We ran our tests with the core clock reduced down to 1 GHz. AMD do not have such models. But top processors can go into this mode, when you choose "performance on demand" in our OS settings or use RMClock. As we used a processor with 512 KBx2 L2 cache, all our clones inherited this parameter. Models with 1 MBx2 cache will be no slower than budget solutions.

We used the ATI RADEON HD 2400 XT graphics card in our tests. This latest-gen graphics card from AMD/ATI has a special unit (UVD) dedicated to video decoding. A similar unit is available in a more expensive family - 2600. However, the top model (2900) does not have it (to be more exact, it has a prev-gen unit with fewer features). So in this case we use a graphics card intended for basic OS features, standard applications, and certainly multimedia. We should note here that it's not the cheapest representative of the series, it's the last but one in the model range. This product costs about 2000 rubles. According to the manufacturer, 2400/2600 cards do not differ in UVD performance. However, the 2600 cards can do postprocessing of higher quality owing to faster memory.

When you browse the results, you should pay attention that "no-acceleration" modes are somewhat exaggerated - if your card supports it, why not use it. It's impossible to test all old cards. So you may try and apply these results to them, taking into account that reality may be better or worse. What concerns integrated graphics, it should be tested individually, because it loads a memory system, which is important in applications we use here. For example, when our motherboard uses integrated graphics, CPU load grows by 10% as opposed to using an external graphics card (no-acceleration mode in both cases).

Optical drives were represented by Optiarc BDRW BD-M100A and Toshiba DVD/HD SD-H802A. Out of doubt, these drives are still too expensive to become popular - Blu-ray drives (unlike HD DVD, there exist BD recorders) cost about $600, while HD DVD (they can just read CD, DVD and HD DVD) can be bought for $260. You can also buy a notebook with a built-in HD drive.

We used a 26" 1366x768 LCD TV-set with HDCP support connected to the computer via DVI. The player was tested in a normal window. But its load did not differ from the full-screen mode. It was proved by additional full-screen tests in 720p and 1080i modes, supported by our TV-set and on a 1920x1200 monitor connected through the analog interface.

Tests were run in Microsoft Windows Vista Home Premium (32-bit version). We'll have to upgrade to this operating system sooner or later. And tests take too much time to rerun them later.

In this test we'll use only Cyberlink PowerDVD 7.3 Ultra with Update 2911, which uses the following codecs: cl264dec.ax - 2.0.0.1709, CLVC1Dec.ax - 2.0.0.6711, CLVSD.ax - 8.0.0.1710, CLVSD_HBD.ax - 8.0.0.6711. Version 3104a available at the time of our tests did not allow to disable DXVA, and it worked incorrectly with some hardware configurations.

It's sometimes important to choose the right version of a player or a driver. Especially as manufacturers are constantly releasing new versions. On the other hand, if a new beta version suddenly improves results, it suggests a sad they-finally-did-it-after-six-months or they-finetuned-it-for-another-test idea. Indeed there are a lot of versions and practically no proofs of improvements. So we decided to use the latest officially available version of drivers. This time it was Catalyst 7.8.

We used the player settings to control hardware-assisted video decode acceleration. Player status during playback was used to inform about DXVA. Even though it's an official mode, the player is not open-source. Only its developers actually know what and how it does it (especially considering its strange behavior with Patch 3104a). On the other hand, this very player is used by real users, so its results are of practical importance. We didn't analyze video quality, but we had not gripes with it during our tests. We'll try to get back to this issue in future. Especially as there have already appeared special test applications.

We monitored the load of PowerDVD on a CPU using system tools. System performance management was disabled, we used RMClock to control CPU clock rates. We played test scenes from our discs in this player, the results obtained for the reporting period were averaged. Video fragments were only five minutes long, approximately 1 GB of data. We also analyzed the CPU load graph in time and visually determined sufficiency of a given hardware configuration for comfortable video playback. The operating system usually automatically disables Aero interface during playback. But we switched to Vista Basic manually before running our tests. Besides, several additional tests showed that PowerDVD loaded the CPU, unlike the other processes that usually loaded the CPU by less than 2%. The acceptable load is 90%. In this case the CPU still has enough resources left for minimal system tasks as well as for variable bitrate (we'll describe this moment later). Insufficient performance looks like freezes in complex scenes. We also noticed problems with audio in case of single-core processors.

Video clips would load the CPU much lower, because they don't require deciphering and usually have a lower bitrate. So if your computer can play discs, it will also cope with clips. On the other hand, clips can be played with another decoder, for example, CoreAVC. It can generate a lower CPU load compared to Cyberlink in no-acceleration mode. So our CPU recommendations may be not optimal - CoreAVC cannot use a graphics card to decode video.