MrNorth:

Hi!

Ok so what are you guys saying? Depending on wether I use  an ATI card or Nvidia card I have to make several settings to display proper color levels.

Yes; at least with a very significant percentage of systems.

If you have an Nvidia card AND an HDTV with an HDMI port AND only use Media Center, things are most likely correct using default settings.

ATI cards always produce washed out SD using default settings and both ATI and Nvidia produce totally incorrect grey levels when hooked up to an HDTV with a DVI port on it.  Nvidia cards also typically produce incorrect grey levels when other applications (such as PowerDVD Ultra and Windows Media Player) are used.

MrNorth:

For my set, I use a Samsung Q96 50" plasma, with HDMI color set to low (as it should be)

When using it with ATI card, it should display the correct black levels? And you mention a difference between HD and SD. How do you make such a difference? If I play PAL 720x576@25i SD TV is this considered SD, while playing a mkv file encoded at 720p considered HD? I dont have blu-ray connected because of the lack of built in support. I buy them together with a friend and he rips them to me.

I'll explain in greater detail below, but with SD content, by default ATI assumes you are displaying source video using the sRGB colorspace (PC/Internet colorspace), not the BT.601 colorspace (SD TV colorspace).  To tell ATI cards that you are using SD source content with a BT.601 colorspace you need to add the "UseBT601CSC" registry setting and set it to "1".  ATI cards do correctly assume all HD content uses the BT.709 colorspace (HD TV colorspace).

I can't recall the exact transition for using the SD vs HD colorspace, but recall it is close to 700 vertical lines for ATI cards.  Your PAL content should be treated as SD so it needs the UseBT601CSC=1 setting to display correctly.

MrNorth:

So generally, an nvidia card should be better to use when you only use media center? I recall somewhere that MS only tested with nvidia cards.

I would in general say this is correct.  The problem I found was with Nvidia cards it was absolutely impossible to get calibrated grey levels simultaneously between Media Center, PowerDVD Ultra and Media Player.  While ATI cards by default output incorrect grey levels for SD, with the right adjustments absolutely everything can be brought into calibration.

MrNorth:

This has been debated over and over again in this forum, and still feels very confusing.

And how do I check if I really have the correct black levels? When I do the calibration in vista media center, everything is ok, but when I play a DVD there is like a gray layer of fog over the entire picture. My picture sources are:

PAL SD TV

PAL DVD

movie files (avi, mkv, etc)

It IS very confusing and this whole situation really takes away from Media Center PCs as being practical devices for the average consumer.

Your "grey level of fog" is due to the SD content being interpreted as an sRGB source.  Adding the registry setting "UseBT601CSC=1" will tell the video card you are using the BT.601 colorspace for SD source content and will fix the problem.

One thing I should add is I've only really researched North American digital video standards in detail.  I understand that PAL vs NTSC do use different black levels when talking about an analog video format, but my (potentially incorrect) understanding is digital black levels are the same; at least as far as modern HDTVs are concerned.  If this is incorrect, please correct me.

I'll add more details in my next post.

To explain further (for digital connections and at least in North America):

• SD TV uses BT.601 ( http://en.wikipedia.org/wiki/CCIR_601 ), which uses a colorspace with a 16-235 range (16-240 for Cb, Cr in YCbCr, 16-235 for Y).  With TVs, RGB with the range of 16-235 is used (DVI TVs) or YCbCr used (HDMI TVs), again with essentially a 16-235 range.  Brightness beyone 16-235 is accepted, but when calibrated 16 and below is black and ~235 and up is full brightness.
• HD TV uses BT.709 ( http://en.wikipedia.org/wiki/Rec._709 ), which uses a colorspace with a true 16-235 range.  Again, some displays need RGB 16-235 and others need YCbCr.
• PC content, Internet content, PC applications, PC video games, etc. all use sRGB, which provides 0-255 grey levels.
• PC monitors use sRGB.  This again is RGB using the full 0-255 range (0 black, 255 full brightness).
• PCs by default output sRGB 0-255 to displays with DVI ports and are supposed to output YCbCr 16-235 to displays with HDMI ports.  Note this means that HDTVs with DVI ports are driven incorrectly.
• ATI (unfortunately for us) made the decision to treat SD source video as sRGB by default (and HD video as required by BT.709).  Nvidia on the other hand decided to treat all source video as either BT.601 or BT.709 by default.
• Some newer HDTVs can be configured to accept sRGB (0-255), but the default is always the colorspaces defined in BT.601 and BT.709 (16-235).

Ultimately this means that when Media Center is being used for TV, the source TV content is typically in the 16-235 range AND it needs to be output to the HDTV in the same 16-235 range.

To make everything reasonably consistent, ATI and Nvidia (for the most part), while processing video, expand the TV format's 16-235 range into 0-255.  At this point almost everything should display correctly on a PC monitor; but if a TV was sent this 0-255, dark scenes are too dark and bright scenes are saturated on the TV.

(I had to split this post for some reason...)

To work around this, there are solutions you can use today (note I have not tried Ian's registry tweaks; perhaps he can comment...):

• If the HDTV uses an HDMI connection, the HDMI specification requires that YCbCr using the 16-235 range be used.  With Nvidia cards when an HDTV with an HDMI port is used, the 0-255 range is compressed into 16-235.  With ATI cards this is only performed when both the ATI HDMI dongle is used AND if the HDTV has an HDMI port.  With ATI, if you use a DVI to HDMI cable to hook up the HDMI display, it is incorrectly sent RGB 0-255 instead.
• If the HDTV uses a DVI connection, both Nvidia and ATI always send RGB 0-255 to the display.  Note that this is totally incorrect and HDTVs always need BT.601 for SD and BT.709 for HD (unless there is a setting you can change to enable sRGB; most TVs don't have this ability).  To work around this you need to use the video control panel to crank up the brightness and turn down the contrast to "fake" an RGB 16-235 output.  With ATI cards an overall setting ("color" setting, not AVIVO) of +31 brightness and 74% contrast is very close to 16-235.
• One thing to note is since all of the video processing from the expansion from 16-235 into 0-255 to the compression back into 16-235 is done by the video card itself, that they don't "really" need to do it when the card knows there is an HDTV hooked up.  In ATI's case I believe they do actually perform both transforms (16-235->0-255->16-235) but they use 10-bit accuracy internally for these 8-bit values and do not loose color accuracy due to round off errors.

As you can see, the situation really is a mess as far as Media Center PCs being used to output to HDTVs, but at least there are workarounds that mostly work.  To be honest, I was not able to get both Media Center and PowerDVD Ultra calibrated properly with Nvidia cards.  With ATI, with a combination of the UseBT601 setting and the right brightness/contrast tweaks I am able to get everything playing to spec on my HDTV (with a DVI/HDCP port).

With the systems I have calibrated with ATI video cards, you need to do the following to get everything right:

HDTV with HDMI port, ATI card using ATI HDMI dongle:

• Add "UseBT601CSC=1" to the registry
• Fine tune your HDTV's brightness/contrast using any calibration source mentioned above, except do not use the included Media Center calibration sources (Ian's sources work perfectly).

HDTV with DVI port, ATI card using ATI HDMI dongle and using an HDMI->DVI cable:

• Add "UseBT601CSC=1" to the registry
• Adjust the overall brightness/contrast to +31/74% in CCC's "color" adjustment.
  Adjust the PowerDVD Ultra advanced video controls (while playing HD-DVD or Bluray) to +19 brightness and -5 contrast
• Fine tune your HDTV's brightness/contrast using any calibration source mentioned above, except do not use the included Media Center calibration sources (Ian's sources work perfectly).

I hope this helps...

MrNorth:

And how do I check if I really have the correct black levels? When I do the calibration in vista media center, everything is ok, but when I play a DVD there is like a gray layer of fog over the entire picture.

Another issue, that answers this question, is for some reason the Vista Media Center calibration video does NOT seem to calibrate the system to use compliant grey levels for TV and DVD content (at least with ATI cards). If you calibrate using the Media Center calibration video, then all of your video will be washed out. I haven't bothered to look at the videos carefully, but my guess is it is an sRGB colorspace source, not a BT.601 source such as TVs use.

On the other hand, Ian Kennedy's personal calibration video (level.wmv) does indeed allow you to ensure that 16-235 is visible on your display for video. If you have an ATI card and no calibration sources, one trick you can use to get your system fairly well calibrated is first using default settings and using the Media Center calibration video to adjust brightness and contrast and then add the UseBT601CSC registry setting.  This first calibrates your display so sRGB SD sources display correctly, and then you tell the video card to treat SD as using the BT.601 colorspace. This should also produce calibrated HD output.

The best way (IMO) to calibrate your system though is to use a series of different calibration sources to make sure everything is correct.

(that was very odd - I had to break up the post into many small pieces until it would be accepted by TGB...)

Ian Kennedy [Iank] provided a link to his personal SD video and image calibration sources in a previous post at http://thegreenbutton.com/forums/post/228161.aspx.  These allow you to ensure the 16-235 range is visible for SD video and at the same time ensure the entire 0-255 range is visible for photograph content. 

His website doesn't seem to have them anymore and I can't add attachments to this web site, but I have attached a copy to a thread over on the avsforums web site www.avsforum.com/avs-vb/showthread.php?p=13939785. Note this thread is full of tons of posts trying to figure out what the heck is going on as far as grey levels output from ATI video cards. What I am posting in this this posting here at TGB is what we eventually figured out after many, many hours of trying to get everything calibrated. If you have an account you can download the "levels.zip" document and this includes Ian's calibration files.

Also in the avsforum thread I have included links to several other calibration sources, including a free HD ramp, a free HD-DVD source, and a free Bluray source.

MrNorth:

So what you say is that nvidia control panel and ATI CCC should be set to YCbCr and not rgb?

Is this always present? On some version of both above products, I have seen this but on my current setup it is gone. Then I guess I have to do a reg hack... as mentioned in the above posts. I will try this when I get home.

There is no way I know of to force the output to YCbCr (or RGB, or RGB 16-235 for that matter).

The PS3 (as an example) has a setting that can be switched between YCbCr, RGB 0-255 and RGB 16-235.  I believe it defaults to YCbCr for HDMI HDTVs and RGB 16-235 for DVI HDTVs.

MrNorth:

My frustration bottles down in that there seem so many players

- tv/projector

I set it to video levels

- gfx card settings

 add the UseBT601CSC = 1 registry entry

- media center settings..

This will set your nominal range to video levels, the current defualt for MCE. Use with properly calibrated consumer displays and projectors. IE: devices set for 7.5IRE blacks.
Windows Registry Editor Version 5.00[HKEY_LOCAL_MACHINE\SOFTWARE\Debug\ehPresenter.dll]
"NominalRange"=dword:2

 After settings this and rebooted, then I am home free?

Does it matter if I use DVI<->HDMI or HDMI<->HDMI. My motherboard supports both.

kind regards

Henrik

If you have an ATI card, DVI to HDMI outputs RGB 0-255 and HDMI to HDMI outputs YCbCr (16-235).  I don't know for certain if a motherboard video solution behaves the same way or not.  Try it.  This difference is extremely easy to see.

I'll probably try the ehpresenter registry edits, but right now I have everything working to spec without it (using the hacks I mentioned earlier).  If this only affects Media Center, then it will likely make it so different video card settings are required between applications with ATI cards.  Possibly it might make Nvidia cards consistent between applications...

Hi!

Thanks for the very lengthy explanation. What surprises me the most is that MS doesn't seem to have done their homework and quality control on this issue, or has the reality changed since the original release?

I changed the reg key and everything became as black as it should be both on SD TV and DVD.

I will do a proper calibration later with DVE, but it feels really bad that I and the VMC users can't trust the calibration video in VMC. Very wierd.

I noticed a strange feature on my samsung TV, it had a setting called "Home theathre PC" which u could set to On an Off. There was no explanation to this in the manual... what this setting does.

Anyway not the gray fog is gone but I lost lots of detail in black areas, like on black shirts.

But the jaggies are still very evident.

Very good thread that ppl from MS, ATI and Nvidia should read.... carefuully.

kind regards

HEnrik

Thanks HT Slider for the detail. You hit the nail on the head with what my issues are with Media Center.

I just wish Microsoft would do something about it, or at least give us some ideas on what they are planning to do about it.

They need to work with a card maker and design a card that can be fully controled via Media Center so it's output would be accurate for HDTV viewing.

If this is going to be the trend (PCs in the living room) and what Microsoft wants, this needs to be done, now, not 3 years from now

BTW, I just checked the video calibration on the PC in my study.  It has an Nvidia PCIe video card, Nvidia driver 175.16 installed and a Viewsonic VP191b monitor (requiring RGB 0-255) connected using DVI.  It is running Vista Home Premium and is fully updated, including SP1.

When I use Ian's calibration source, my Avia calibration DVD, or other downloaded calibration sources:

• In Media Center, the full 0-255 is visible and video content is washed out and looks terrible.
• In Media Player or PowerDVD, it is perfectly calibrated, 16-235 is visible and video content looks great.

When I use the Media Center grey level calibration videos:

• In Media Center, these videos appears to be well calibrated (although we know it is not properly calibrated and 0-255 is actually visible).  This proves that the Media Center calibration videos calibrate closer to sRGB, not the proper TV/DVD (BT.601 or BT.709) colorspace.
• In Media Player or PowerDVD, the X is not visible and the shirt is washed out.  Again this proves that the Media Center calibration videos are calibrated for something other than TV/DVD.

Ian, can you please comment on this?  Why are the Media Center calibration videos not designed to calibrate for a proper TV or DVD colorspace?

Also, why would Media Center be the only application that fails grey level tests using default settings when using your calibration video (levels.wmv), using the Avia calibration DVD, and when using other downloaded calibration videos?  I would have thought that if anything Media Center would be the application that DOES display video correctly when using a PC monitor.  Obviously when a PC monitor is used, BT.601 and BT.709 needs to be expanded to sRGB - but this isn't happening.

Also, I thought for a minute that maybe Media Center always outputs everything calibrated for an HDTV, but that doesn't make sense either because I see photographs are being output using sRGB in Media Center (tested using your levels.bmp) and they are not being converted to the BT.709 colorspace.

Essentially with an Nvidia video card using default settings, Media Center's video is output using BT.709 (incorrect for my monitor) and photographs are output using sRGB (correct or my monitor).  If I was to instead send this output directly to my HDTV, video would be correct but photographs would be incorrect.

Do all Nvidia cards work this way?  With ATI cards (as long as UseBT601CSC is set) they convert "most" output (video and photographs) to the appropriate colorspace (BT.709 when an HDTV w/HDMI is used and sRGB when a PC monitor is used).

Edit:  I tried Ian's

This will set your nominal rante to 0-255 (PC levels) essentially doing "expanded blacks" use this with a typical PC monitor calibrated for blacks==0.
Windows Registry Editor Version 5.00[HKEY_LOCAL_MACHINE\SOFTWARE\Debug\ehPresenter.dll]
"NominalRange"=dword:1

and for some strange reason it didn't do anything.  My Viewsonic monitor is still being fed non-expanded 16-235 video.  Is my Nvidia 6800 "too old" to support this setting or something?

I think I'm going to pull the ATI 2600XT out of the basement and see what happens in this PC.  Can ATI properly expand BT.601 and BT.709 to convert it to sRGB (0-255) so it looks correct on a monitor?

tmbn:

VMC has poor quality regardless of the source. I use the same source and Cyberlink PowerCinema has alot of better quality in the picture. Why hasn't Microsoft allowed us to change MPEG-2 decoder (or any other decoder) in Vista Media Center. An option like this would change VMC from hell to heaven. It seems like Microsoft has somewhat given up entering our living room. As it was mentioned here, they are so far behind.

Although I've been complaining about grey levels (primarily), once I added the necessary tweaks for my HIS 3870 IceQ (or previous ATI 2600XT), I have actually been fairly pleased with the image quality.

In my case if I compare the image quality between my STB and Vista Media Center/3870, the image is considerably better with Media Center.

Note that my STB is an old Bell 6000 (component out) and I digitally record using an R5000HD mod (and FireSTB) and digitally send the video output to my HDTV (DVI).  The STB itself does a terrible job of deinterlacing (if I ask it to) as well as an absolutely terrible job of scaling (again if I ask it to).  If I use it to simply output using 720p or 1080i and the content is in the same format, then the image quality is about the same as Media Center.  If I use it to simply output 480i in 480i, it looks terrible again, but now because my HDTV does a terrible job of deinterlacing and scaling it to 720p or 1080i (depending on the setting). 

As a result, 480i looks much better through the Media Center PC when upconverted to 1080i (the HDTVs native format) vs the STB and 720p/1080i looks just as good as directly from the STB.

A few things I find a little odd though:

1. When watching 1080i content, even though I know it is first deinterlaced and then interlaced again, there are very few deinterlacing issues that are obvious.  I often wonder if the nature of re-interlacing it hides some deinterlacing flaws.
2. When watching the same 1080i content using my fathers Media Center PC and TV (ATI 2600Pro and Olevia 1080p LCD HDTV), there are many more deinterlacing flaws visible.
3. When watching 480i content on either system, there are more visible deinterlacing errors than with 1080i content.  Once in a long while it seems to loose track of the detinterlacing and really messes it up too (both systems; mostly with originally 24p film content).
4. With the exception to Bluray/HD-DVD content, Recorded TV (480i, 720p & 1080i) actually looks better on my 51" 1080i HDTV when compared to my fathers 47" 1080p HDTV.  Bluray/HD-DVD in 1080p does look quite a bit better on the 1080p HDTV though.  We even sit closer to my 51" HDTV (~7 feet away) compared to my fathers 47" HDTV (~8.5 feet away).

Another thing to note is it is quite easy to change the MPEG-2 decoder that Vista Media Center uses.  I've tried many different ones and can't honestly say any look better than Microsoft's MPEG-2 decoder.  Some do start up faster, skip/replay faster, and produce a cleaner image during skip/replay (all of this is only noticeable with HD content).

If you want to experiment with the decoder, you just need to install a different decoder and then use the Vista Media Center decoder utility (http://mediacenterexpert.blogspot.com/2006/07/vista-media-center-decoder-utility.html) to flip between them.  You can also do it manually through the registry if you prefer.

rgreenpc:

Every time I have ever tried changing the codec I get content issues with shows.

Same here, my channel to try to see if I have an issue is "AMC" if I change codecs, this channel will give me "restricted content". I know if I get this error, I'll have assorted issues with recording shows on the major networks (NBC mainly)