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.
Facebook
Twitter
RSS
70 Comments
View All Comments
ganeshts - Thursday, June 16, 2011 - link
PotPlayer apparently doesn't have support for hardware deinterlacing, and has a host of other issues [ Search for PotPlayer in this page and then read the next set of posts about it : http://www.avsforum.com/avs-vb/showthread.php?p=20... ].Of course, if it works for you, it is great :) (probably it is a good solution for people watching progressive material only).
The author of LAV CUVID talks in that thread about how renderless DXVA mode works with madVR at the cost of deinterlacing.
Btw, there is no decode of DTS-HD in any open source software now. Both ffdshow and PotPlayer can decode only the core DTS soundtrack. DTS decode has been around for a long time, though.
NikosD - Saturday, June 18, 2011 - link
Indeed, I was referring to progressive material only - interlaced material is rare - but the page you mentioned says PotPlayer has CPU deinterlacing.I don't see where is the problem.
Hardware Deinterlacing is less important - for most users - than Hardware Decoding (DXVA) and less important than the UNIQUE capability of using DXVA + madVR at the same time.
The cost of hardware deinterlacing is nothing compared to the cost of DXVA and madVR.
For the audio part of your answer, I have to say that because of my AVR (Pioneer VSX-920) decoding inside a PC, BluRay, Media Player or any other decoding capable device of multi-channel audio is never an option for me.
I always prefer the bitstreaming solutions for multi-channel audio - as most of the owners of AVR do - like those provided by FFDshow and PotPlayer which both are more than capable of providing them.
That's why I wrote "decoding and pass-through", I had to write "splitting and pass-through".
One last word.
For every piece of software out there, there is always a list of changes, bugs, things to do.
That doesn't mean we don't use it or like it.
PR3ACH3R - Friday, June 17, 2011 - link
@Ganesh T S,This is some NICE work.
In fact, I cannot recall when was the last time I have seen such an in depth article on the HTPC GPU subject in Anandtech.
The balance between the technical issues, the background, & the effort to honestly report all issues known to you in this article, is spot on.
If it is missing something on the issues report, it misses on the ATI/AMD DPC Latency spiking issues.
As this is still remains unnoticed in Anandtech even in this excellent article, here is a link to the AVS post describing it.
http://www.avsforum.com/avs-vb/showthread.php?t=12...
(Ignore some of the discredit attempt posts in this thread, this problem exists to this very day.)
NikosD - Thursday, June 23, 2011 - link
Well, I did some further tests and found out that PotPlayer does have hardware deinterlacing.Have you done any tests by yourself to see if the player supports Hardware Deinterlacing ?
ganeshts - Saturday, June 25, 2011 - link
NikosD, I will definitely try PotPlayer out in the next GPU review. Till now, my knowledge is limited to what is there in the AVSForum thread.flashbacck - Friday, June 24, 2011 - link
I know HTPCs are even more of niche these days than ever, so I appreciate you still doing these tests very much.wpoulson - Thursday, July 28, 2011 - link
I really appreciate this guide and have been stepping through itI just registered the ASVid.ax file from TMT5 but the filter is not showing up in the External Filter section of MPC-HC. At first I thought it might be because I registered it on the 32 bit side and I'm using 64 bit MPC-HC, so I unregistered the file from System 32 and registered it on the 64 bit side.
I registered it by going to Start>CMD>Cntrl-Shift-Enter and using the "Regsvr32" command to register the file. I put the file along with the checkactivate dll in a folder in the root directory of my C drive and pointed the Regsvr command to the ASVid.ax file. After hitting enter, I received a "dll successfully registered" message.
Can someone help me to get the filter visible for MPC-HC?
A question...While it's considered beta, will the new LAV video decoder do the same thing the arcsoft video decoder does?
Thanks
Warren
stuartm - Friday, January 20, 2012 - link
I am aware the gt 430 is a good choice to work around the infamous WMC 29/59 framerate bug. Can you comment on whether or not the 6570 will stutter or not when playing content with 29/59 framerate problems? A very important consideration for those of us using ceton or HDHR Primes (or the new Hauppauge box) for cable TV Live viewing and record/replay.Thank You
MichaelSan1980 - Saturday, January 21, 2012 - link
I'd use my HTPC for DVD's and BD's only with an Full-HD TV. Since i have a rather strong CPU and wouldn't use Hardware Deinterlacing for DVDs, i wonder, if the GT520 is ~that~ bad, in terms of image quality?drizzo4shizzo - Wednesday, June 20, 2012 - link
Old guy here.In the market but I need confirmation that these cards can do component output to "old guy" HDTV.
NONE of the marketing materials suggest that any recent card can.
Meaning they either come with a component video breakout or at least are compatible with a known 3rd party product, and that they can do the RGB -> YUV thing.
This ancient EVGA 7600 GT I have does it... with an "svideo lookalike" 7 pin -> component breakout.
Anyone? Beuller?