Discrete HTPC GPU Shootout
by Ganesh T S on June 12, 2011 10:30 PM ESTOne of the video post processing aspects heavily emphasized by the HQV 2.0 benchmark is cadence detection. Improper cadence detection / deinterlacing leads to the easily observed artifacts during video playback. When and where is cadence detection important? Unfortunately, the majority of the information about cadence detection online is not very clear. For example, one of the top Google search results makes it appear as if telecine and pulldown are one and the same. They also suggest that the opposite operations, inverse telecine and reverse pulldown are synonymous. Unfortunately, that is not exactly true.
We have already seen a high level view of how our candidates fare at cadence detection in the HQV benchmark section. In this section, we will talk about cadence detection in relation to HTPCs. After that, we will see how our candidates fare at inverse telecining.
Cadence detection literally refers to determining whether a pattern is present in a sequence of frames. Why do we have a pattern in a sequence of frames? This is because most films and TV series are shot at 24 frames per second. For the purpose of this section, we will refer to anything shot at 24 fps as a movie.
In the US, TV broadcasts conform to the NTSC standard, and hence, the programming needs to be at 60 frames/fields per second. Currently, some TV stations broadcast at 720p60 (1280x720 video at 60 progressive frames per second), while other stations broadcast at 1080i60 (1920x1080 video at 60 fields per second). The filmed material must be converted to either 60p or 60i before broadcast.
Pulldown refers to the process of increasing the movie frame rate by duplicating frames / fields in a regular pattern. Telecining refers to the process of converting progressive content to interlaced and also increasing the frame rate. (i.e, converting 24p to 60i). It is possible to perform pulldown without telecining, but not vice-versa.
For example, Fox Television broadcasts 720p60 content. The TV series 'House', shot at 24 fps, is subject to pulldown to be broadcast at 60 fps. However, there is no telecining involved. In this particular case, the pulldown applied is 2:3. For every two frames in the movie, we get five frames for the broadcast version by repeating the first frame twice and the second frame thrice.
Telecining is a bit more complicated. Each frame is divided into odd and even fields (interlaced). The first two fields of the 60i video are the odd and even fields of the first movie frame. The next three fields in the 60i video are the odd, even and odd fields of the second movie frame. This way, two frames of the movie are converted to five fields in the broadcast version. Thus, 24 frames are converted to 60 fields.
While the progressive pulldown may just result in judder (because every alternate frame stays on the screen a little bit longer than the other frame), improper deinterlacing of 60i content generated by telecining may result in very bad artifacting as shown below. This screenshot is from a sample clip in the Spears and Munsil (S&M) High Definition Benchmark Test Disc
| Inverse Telecine OFF | Inverse Telecine ON |
Cadence detection tries to detect what kind of pulldown / telecine pattern was applied. When inverse telecine is applied, cadence detection is used to determine the pattern. Once the pattern is known, the appropriate fields are considered in order to reconstruct the original frames through deinterlacing. Note that plain inverse telecine still retains the original cadence while sending out decoded frames to the display. Pullup removes the superfluous repeated frames (or fields) to get us back to the original movie frame rate. Unfortunately, none of the DXVA decoders are able to do pullup. This can be easily verified by taking a 1080i60 clip (of known cadence) and frame stepping it during playback. You can additionally ensure that the refresh rate of the display is set to the same as the original movie frame rate. It can be observed that a single frame repeats multiple times according to the cadence sequence.
Now that the terms are clear, let us take a look at how inverse telecining works in our candidates. The gallery below shows a screenshot while playing back the 2:3 pulldown version of the wedge pattern in S&M.
This clip checks the overall deinterlacing performance for film based material. As the wedges move, the narrow end of the horizontal wedge should have clear alternating black and white lines rather than blurry or flickering lines. The moire in the last quarter of the wedges can be ignored. It is also necessary for both wedges should remain steady and not flicker for the length of the clip.
The surprising fact here is that the NVIDIA GT 430 is the only one to perfectly inverse telecine the clip. Even the 6570 fails in this particular screenshot. In this particular clip, the 6570 momentarily lost the cadence lock, but regained it within the next 5 frames. Even during HQV benchmarking, we found that the NVIDIA cards locked onto the cadence sequence much faster than the AMD cards.
Cadence detection is only part of the story. The deinterlacing quality is also important. In the next section, we will evaluate that aspect.
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casteve - Monday, June 13, 2011 - link
I hope to see a review of the HD 6670, now that (at least) Sapphire has released a passive version.Drae - Monday, June 13, 2011 - link
... it'd be nice to see more use of Linux please. I realise there are a lack of "testing" and "evaluation" tools under Linux but that shouldn't prevent the testing of basic media needs. What's this about no bit streaming support under Linux? Boxee would disagree - as would:http://phoronix.com/forums/showthread.php?27348-Tr...
along with XBMC's audioengine (involving work by the guy in the above link). Maybe Windows 8 will sort out the mess that is WMC and all the messing (or bypassing with MPC-HC) that is required to get it working solidly. But right now if you want something that approaches a plug and play media experience XBMC (and its off-spring Openelec) under Linux is a lot closer than Windows. Equally the more coverage such solutions get the more likely greater time will be spent fixing the remaining issues under the Linux OS - hello there Intel and AMD.
Finally there is a great move now - go look at AVS' fora for examples - away from large media center pc's to small, quiet (silent) systems. These don't require 300W or 500W power supplies and huge cases with twelve fans and fifty million led's. They are ITX based systems sitting in small ITX sized boxes running 65/80/90/120W PicoPSU's with much greater efficiency and thus lower power use/running costs/silence. Placing these discrete cards in such systems would be a nice test of these picopsu units - given the apparently low power draw shown in the articles (something I'm very interested in seeing right now given the poor support of Linux by Intel on Sandybridge - the GT430 would be a good interim solution for me).
TLDR: Please don't limit yourselves to Windows testing and ATX/mATX sized systems when writing HTPC articles
ganeshts - Monday, June 13, 2011 - link
Drae, Thanks for the info and the link.The issue with Linux HTPCs is the fact that there is a semblance of support from only NVIDIA.
Don't get me wrong! I am a huge Linux fan, and always prefer free / open-source software. But, from a video perspective, is there a multi-GPU platform similar to DXVA ? Every vendor has their own flavour (NVIDIA - VDPAU / Intel - VA-API / AMD - XvBA). From the audio side, it looks like the link you mention is the only avenue available for bitstreaming, and that too for NVIDIA GPUs only. I will keep close tabs on what is happening in this area, and when the time is right, I will definitely post a piece on Linux HTPCs, considering one card from each of the vendors.
cjs150 - Tuesday, June 14, 2011 - link
As always it depends on what you want from an HTPC. For me I want to play Blu rays, stream HD movies from file server, watch and record TV and do some web browsing but in total silence (or as close to as possible).For me ITX systems are the way to go using a 150W PICO-pSU but critical is that they have to work with appropriate IR remote (Logitech DiNovo looks interesting)
I am happy to use Linux or Windows but it just has to work
alfredska - Monday, June 13, 2011 - link
This kind of quality review is what made AnandTech a name to remember early on. I'm glad to see such thoroughness and well thought out presentation of information. Looking forward to more reviews by Ganesh.UrQuan3 - Wednesday, June 15, 2011 - link
Agreed, this is an excelent article. I tried cross referencing to the "Zotec Zbox" article from the 9th (I own an E-350) and the earlier benchmarking was useless. I already know the E-350 won't do full processing, but I wanted to know where it sits compared to these platforms that pull 3-10 times the power.Think a 'software mode' might have been useful? An i5 could have done a fair amount of this processing without a hardware assist, saving the 70watts the cards were pulling and avoiding some of the integrated's compatability issues.
Shadowmaster625 - Monday, June 13, 2011 - link
I dont get the video card focus in the realm of HTPC. It seems that software is a far more important piece of the picture than a video card. Windows media center and XBMC both work like crap, and/or are unacceptably slow and clunky when it comes to browsing media. I do NOT tolerate that kind of lag, especially on a 3 ghz quadcore with an ssd/hdd drive setup. I dont expect miracles when trying to browse through a gigabyte of media, but still it should be faster. And then there's audio sync problems that like to appear out of nowhere. But you'd never know any of these problems exist from reading these articles. Shrug.I have found that VLC media player and windows explorer are the most reliable combination. But using windows explorer on an htpc is ugly and painful.
JasonInofuentes - Tuesday, June 14, 2011 - link
I think part of the problem is the degree to which there's news. A thorough review of Media Center might be warranted, the next time it changes, but was pretty thoroughly covered here (http://www.anandtech.com/show/2864/) and here (http://www.anandtech.com/show/2760). XBMC has a more frequent update cycle than Windows, and there's obviously interest so this might be an idea to explore further.As far as the difficulties with each of these platforms, a Z68 platform and SRT might be the solution here. So the size of the files is not really the problem, it's that when you browse to a folder the user wants to be able to scroll around the list or grid and have all of the information pertinent to those files readily available. You don't want to scroll over to a file in your West Wing Season 5 folder and wait for the Title to load so you know whether it's the episode you were looking for, you want that information to be up the instant you scroll to it, or even better for it to be glanceable before you even start scrolling. In order to achieve this the OS's load all of the information for all of the files in the folder. So if you have a few dozen files in a folder that's the metadata for each files, the thumbnail preview and then the usual file system queries the OS would do anytime it accesses the drive. That can add up to a lot of small reads, and that leads to that big stall as you scoot around your media.
Now, the throw money at it solution is move to ALL SSD storage. But I've got 4TB of media and don't have that kind of money to throw at the problem. SRT should help though. If I recall, the metadata and thumbnail files are stored locally in the folder with the files, but since SRT caches the frequently accessed files, then for a system used exclusively for media the only thing that should populate the SSD cache is going to be these small reads that otherwise slow down your system.
I am suddenly overwhelmed with an urge to get my hands on a Z68 to try this out! And you are quite right that VLC and Windows Explorer are the most reliable programs for browsing and playing back media, but the price you pay for pretty is often performance.
vailr - Monday, June 13, 2011 - link
As an exercise in "possibility thinking", I'd be interested in a sub-category of a complete "solar powered" desktop-format PC review. Designed (theoretically) for someone living in a remote area, off the electrical grid, yet still having internet via satellite, cell phone signal, or otherwise connected. Designed for ultra low power consumption, mostly dependent on solar and/or wind power produced on site. Yet maximal possible performance (under such power restrictions) for either: generic gaming desktop PC, and also for a HTPC. Using SSD's and/or laptop HD's for storage, and with an energy sipping CPU (dual-core Atom vs. Intel i330, for example), combined with either: on-CPU chip video or a "PCIe bus only" powered video card, and yet somewhat viable as a gaming PC or as a HTPC.Maybe even qualify for an article in Home Power magazine? http://homepower.com
Penti - Monday, June 13, 2011 - link
Why? Running a 100 W PC of batteries is pretty pointless.Just install FTTH and a powerline if you like to game or do other intensive tasks needing GPU-power, fast cpus or ridiculous amounts of memory (workstation type stuff). It would be the most efficient solution any way. You don't even need any power for any modems. You certainly can run a PC of battery power off grid, but why destroy your work with that. It would be hard to store much electrical power.
Otherwise you would pretty much had to get by with a low-powered laptop. No monitor.
Do the unabomber type guys need any gaming? If so they need to install a good damn power line or at least a diesel-generator. They don't have the money and skills to build energy storage and buy panels thats enough to power a modern home any way.