Original Link: https://www.anandtech.com/show/2168
Coming Soon to HD DVD: Silicon Optix HD HQV
by Derek Wilson on February 8, 2007 1:25 AM EST- Posted in
- GPUs
Introduction
In the past, when testing video playback features of PC graphics hardware, we have looked at the HQV benchmark by Silicon Optix. Over the years, HQV scores have improved, as we can see when comparing our first article on the subject to one written four months later. Current scores are nearly perfect on both NVIDIA and AMD hardware. But there is something lacking in these tests: they only provide insight into how hardware performs when handling standard definition content.
With the introduction of HD DVD and Blu-ray content, we have been waiting for a benchmark with which to test image quality of HD playback. Graphics hardware may ultimately have less of an impact on the HD viewing experience in the long run because media and players natively support 1080p, but it is still an important link in the chain. Interlaced media is available on both HD DVD and Blu-ray, and high quality deinterlacing at HD resolutions is just as important as it is on DVDs.
The benchmark not only looks at deinterlacing quality, but noise reduction as well. Noise can actually be more of a problem on HD video due to the clarity with which it is rendered. While much of the problem with noise could be fixed if movie studios included noise reduction as a post processing step, there isn't much content on which noise reduction is currently performed. This is likely a combination of the cost involved in noise reduction as well as the fact that it hasn't been as necessary in the past. In the meantime, we are left with a viewing experience that might not live up to the expectations of viewers, where a little noise reduction during decoding could have a huge impact on the image quality.
There are down sides to noise reduction, as it can reduce detail. This is especially true if noise was specifically added to the video for effect. We don't run into this problem often, but it is worth noting. On the whole, noise reduction will improve the clarity of the content, especially with the current trend in Hollywood to ignore the noise issue.
We have wanted to play with an HD version of HQV for a while, and we are glad to have our hands on this early version. Before we take a look at just how the competition stacks up, we will look at the tests themselves and Silicon Optix scoring system.
The HD HQV Tests
The version of HQV Silicon Optix provided for us contains tests for a couple different aspects of HD video decoding: noise reduction, resolution loss, and deinterlacing artifacts (jaggies). We will break down the specifics of each test and talk about what we are looking for. This time around, Silicon Optix's scoring system is broken down with more variability in each test, but we will try to be as objective as possible in our analysis.
Noise Reduction
The first test in the suite is the noise reduction test which is broken down into two parts. Initially, we have an image of a flower that shows large blocks of nearly solid color without much motion. This tests the ability of the video processor to remove spatial noise.
When no noise reduction is applied, we see some static or sparking in the flower and background. Hardware will score higher the more noise it is able to eliminate without introducing any artifacts into the image.
The second test that looks at noise reduction presents us with a scene in motion. It is more difficult to eliminate noise while keeping objects in motion crisp and clear. In this test, we are looking for noise reduction as well as a lack of blurring on the ship.
Scoring for these tests ranges from 0 to 25, with the highest score going to hardware that is able to reduce noise while maintaining a clear image that has no artifacts. While Silicon Optix has stated that scores can range anywhere from 0 to 25, they break down four suggested scores to use as a guide. Here's the breakdown:
25 - The level of noise is noticeably reduced without loss of detail
15 - The level of noise is somewhat reduced and detail is preserved
7 - The level of noise is somewhat reduced but detail is lost
0 - There is no apparent reduction in noise and/or image detail is significantly reduced or artifacts are introduced.
Until we have a better feel for the tests and the variability between hardware, we will stick with only using these delineations.
Video Resolution Loss
After noise reduction, we look at video resolution loss. Resolution loss can occur as a result of deinterlacing, and effectively reduces the amount of information that is displayed. In interlaced HD video, alternating fields display odd and even scanlines of one image. Simple deinterlacing techniques can choose to simply duplicate the data in the first field and toss out the rest of the information, and others will simply average the data in two fields together to create a frame. Both of these techniques have issues that cause artifacts, and both remove detail from the image.
When objects are not in motion, interlaced fields can simply be combined into one frame with no issue, and good hardware should be able to detect whether anything is moving or not and perform the appropriate deinterlacing method. In order to test the ability of hardware to accurately reproduce material from interlaced video in motion, Silicon Optix has included an SMPTE test image at 1920x1080 with a spinning bar over top to force hardware to employ the type of deinterlacing it would use when motion is detected. In the top and bottom left corners of the SMPTE test pattern are boxes that have alternating black and white horizontal lines that are one pixel wide. A high quality deinterlacing algorithm will be able to reproduce these very fine lines, and it is these that we are looking for in our test pattern.
Interestingly, AMD, NVIDIA, and PowerDVD software all fail to adequately reproduce the SMPTE resolution chart. We'll have to show a lower resolution example based on a smaller 512x512 version of the chart, but our comments apply to the full resolution results.
If the hardware averages the interlaced fields, the fine lines will be displayed as a grey block, while if data is thrown out, the block will be either solid black or solid white (depending on which field is left out).
Scoring for this test is an all or nothing 25 or 0 - either the hardware loses resolution or it does not.
Jaggies
A good deinterlacing algorithm should be able to avoid aliasing in diagonal lines apparent in less sophisticated techniques. This test returns from the original standard definition HQV test, and is a good judge of how well hardware is able to handle diagonal lines of varying slope.
Here we want each of the three lines to maintain smoothness while moving back and forth around part of the circle. Scoring is based on a sliding scale between 0 and 20 with suggested breakdowns based on which bars maintain smooth edges. We will again be sticking with a score that matches the suggested options Silicon Optix provides rather than picking numbers in between these values.
20 - All three bars have smooth edges at all times
10 - The top two bars have smooth edges, but the bottom bar does not
5 - Only the top bar has a smooth edge
0 - None of the bars have smooth edges
Film Resolution Loss
This test is nearly the same as the video resolution loss test, and the score breakdown is the same: 25 if it works or 0 if it does not. This time around, interlaced video of the SMPTE test pattern is generated using a telecine process to produce 1080i video at 60 fps from a 24 fps progressive source. Because of the difference in frame rates between video and film, a 3:2 cadence must be used where one frame of film is stretched across 3 interlaced fields and the next frame of film is stretched across 2 fields.
One major advantage of this process is that it is reversible, meaning that less guess work needs to go into properly deinterlacing video produced from a film source. The process of reversing this 3:2 pulldown is called inverse telecine, and can be employed very effectively to produce a progressive image from interlaced media. If this is done correctly, no resolution needs to be lost.
Rather than having a moving bar over top of the test pattern, the image shifts back and forth from left to right and resolution loss can make the image appear to strobe or produce the appearance of vertical lines along the edges of fine lines.
Film Resolution Loss - Stadium Test
The final test is a practical test of film resolution loss, showing what can happen when a film source is not accurately reproduced. In this case, flickering in the stadiums or a moiré pattern can become apparent.
Scoring for this test is another all or nothing score granting the video decoder being tested either a 10 or a 0.
Now that we've gotten familiar with these tests, let's take a look at how AMD and NVIDIA stack up under HD HQV.
HD HQV Performance
For these tests, we will be using a beta version of PowerDVD HD 6.5 along with hardware acceleration to play back the HD HQV HD DVD. This works much the same as it did with the standard definition HQV test which is a collection of clips playback from a DVD. The software DVD, HD DVD or Blu-ray player, with hardware acceleration enabled, will use the graphics hardware to offload the decode process from the CPU. The byproduct of this is that image quality is more influenced by the hardware being used than the software when using hardware acceleration.
For AMD we are using Catalyst 7.1, and for NVIDIA we look at 93.71 for the 7 series and 97.92 for the 8 series. Our results on both 7 and 8 series cards for NVIDIA are the same, so there will be no distinction between the two when talking about NVIDIA results. This comparison is as much between AVIVO and PowerDVD HD as it is of the hardware at this point. Both AMD and NVIDIA should have some headroom for improving performance through their drivers in the future.
The maximum score for HD HQV is 105 with 80 of those points having to do with proper deinterlacing of interlaced HD sources. All broadcast HD sources in the US today are interlaced, and there are many HD DVD movies provided in 1080i as well. Fewer Blu-ray titles are 1080i, but they aren't impossible to find. While our HD DVD version of HQV obviously tests HD DVD players, these features will be important for the playback of any interlaced HD source. Because of this, we really expected NVIDIA and AMD to perform well.
Unfortunately, reality did not live up to our expectations. We'll break it down by test. While we would love to provide screenshots, our version of PowerDVD doesn't support screenshots, and taking pictures of the TV just doesn't provide the detail we need. Descriptions of what's going on will have to do for now.
Noise Reduction
Both AMD and NVIDIA score a flat zero on this test. None of the AMD or NVIDIA cards we tested performed any noise reduction on either the flowers or the boat scene. There weren't any artifacts present, but it is very clear that neither camp performs any noise reduction on HD video at this point.
Video Resolution Loss
AMD averages fields and thus looses detail. The result is a gray color filling the corner blocks rather than alternating fine lines. NVIDIA doubles the scanlines in one field and eliminates half of the data, as the corner blocks are solid colors. This means that both solutions fail in different ways. PowerDVD's software performs similarly to AMD hardware, which means that currently available computer hardware and software will not faithfully reproduce interlaced video.
Jaggies
Once again, AMD and NVIDIA both fail to eliminate diagonal aliasing. This is another example of the poor deinterlacing provided by computer hardware and current drivers. Eliminating jaggies is a major way to improve the visual experience of watching interlaced video on a progressive display like a 720p or 1080p HDTV or a computer monitor.
Film Resolution Loss
Like the video resolution loss test, both NVIDIA and AMD fail this test. The failure was a result of the same problems we saw in the video resolution loss test, meaning that rather than performing inverse telecine, both AMD and NVIDIA treat 1080i created from a film source the same way they would treat video. For AMD this means averaging fields, and for NVIDIA this means eliminating half the fields.
Film Resolution Loss - Stadium Test
When playing on AMD hardware, flickering is apparent in the stadium. While NVIDIA hardware doesn't flicker, a moiré pattern is apparent in the stands. Both of these fail to pass the test and demonstrate different issues that can appear when film is poorly deinterlaced.
The overall result?
AMD: 0
NVIDIA: 0
Final Words
This is one of those times summing up is easy: both AMD and NVIDIA fail utterly at every test HD HQV throws at them. Advanced deinterlacing algorithms used on standard definition video are just not present when working with HD video. We are lacking inverse telecine and noise reduction as well. Watching interlaced HD content on a progressive scan monitor using a computer is not going to deliver an optimal experience until AMD and NVIDIA get with the program and start extending their image quality improving algorithms to HD interlaced content.
While watching 1080p content using a modern graphics card will not have many of the issues illuminated by HD HQV, noise reduction would definitely help. With higher resolution content, issues like noise are actually more noticeable and distracting. Ideally, movie studios would perform noise reduction on their content before encoding it for distribution, but this just doesn't happen right now.
With cable and satellite carrying interlaced video, watching TV and recorded content on the computer will be the more important benefactor of high quality deinterlacing support on graphics hardware. Of course, owners of 1080i HD DVDs and Blu-ray movies won't want to be overlooked. It could be argued that good deinterlacing is more important on cable boxes or TVs, but stand alone HD DVD and Blu-ray players are out there that provide higher quality deinterlacing and noise reduction than can currently be achieved on a PC. In fact, Silicon Optix not only makes the HD HQV benchmark, but their HQV line of video processors featured in high end consumer electronics devices is designed to pass all of the tests featured in their benchmark.
We certainly hope AMD and NVIDIA will pay some much needed attention to their HD video processing and address the issues we've seen here. As many of the techniques used in standard definition video processing can be extended to HD processing, we hope that future driver updates will make things more interesting. If and when we see something more interesting happen on PC graphics hardware, we will revisit the issue. We also plan on comparing the PC and consumer electronics hardware in the future as well.