I already have a properly calibrated display (white/black levels, grayscale only, no CMS).

I recently added a HTPC into the mix. It's connected using HDMI/RGB. Is there any benefit to completing a calibration to define an ICC profile on the PC?

I have done similar calibrations on my computer monitors using the software available from X-rite/i1Display (for photo editing). But I'm not sure what would happen if I had a "double" (redundant?) calibration. I figure either I wreck the system, or perhaps gamma and/or color points might get refined a bit.

I already have a properly calibrated display (white/black levels, grayscale only, no CMS).

I recently added a HTPC into the mix. It's connected using HDMI/RGB. Is there any benefit to completing a calibration to define an ICC profile on the PC?

I have done similar calibrations on my computer monitors using the software available from X-rite/i1Display (for photo editing). But I'm not sure what would happen if I had a "double" (redundant?) calibration. I figure either I wreck the system, or perhaps gamma and/or color points might get refined a bit.

If the display was done properly the ICC is likely to cause more harm than good. The HTPC would need to be properly setup though.

My HTPC to Projector had issues with the color space and what I'm going to blame on Projector firmware caused a random color space on my display. It took me quite a while to nail down. My pj was set to Auto Color Space and with it changing at will, I had a hell of a time calibrating that thing.

At least in my case, I had to manually set the colorspace in order to be able to calibrate. Otherwise, I'd get a disk looking incredible, and then 2 days later I'd show it to someone and say, "wth? this isn't right??? ". Well, no it wasn't...

So I guess to answer your question, I'd say yes, I'd calibrate for the HTPC and set a new profile vs the other source components you have now.

(Then I'd let the display drivers alone, for quite some time... LIke forever.)

It's up to the playback app/drivers to figure out rec.709 vs rec.601 colorspace issues, but typically what happens is that the PC is native for rec.709/sRGB primaries.

The other bit that is an issue is levels.
PCs runs 0-255
Video runs 16-235

So you may want to check your calibration to make sure the video coming out of the PC is where you expect it to be.

Some funny things can happen to your signal regardless if you're using RGB or YCrCb so comparing some 10% measurements between a standalone player and video playback on the PC and then possibly also the raw desktop on the PC might be a good idea to make sure your levels are where you expect them to be.

Black levels are really the gotcha in integrating a PC. ICC stuff isn't worthwhile because none of the players really support it.

Once you get the black levels dialed in on the PC, updating the video card LUT to work as a video equalizer to nail your gamma and white point can be done, but currently their isn't any software designed for HTPC use that does that.

If your running wih a lutted source the proced ure is generaly thus:

maximise the contrast capabilities of the display without clipping, calibrate the grayscale to D.65. ( a normal calibration of grayscale and brightness)

Profile display by metering the whole display loop (generate test patches from the source ie HTPC) : calculate and apply correctional LUT to take care of gamut and gamma. to take the display to a desired standard(s)

Real world:

sometime maximising contrast and calibrating grayscale are not mutually compatable...the solution usually involves you getting familiar with the capabilities of a given display or at least knowing/feeling its foibles and real; world capabilities. Thankfully most decent displays can usually manage both these days.

Digital displays generally are lacking in precision: by that I mean rendering an 8bit or greater grayscale without visible banding. Good Lcds managed about 6bit a couple of years ago genrelly you have to pay huge wonga to get close to 8bit and even then if you were strict most don't get there. ( this is what modulated per pixel backlighting is all about )

So you need to make the most of the available precision by letting the display scale its white point to the brightest it will go without clipping (especially with video). Otherwise banding city.

Technically this makes the display out of spec in terms of video standards that define a white point. In practice its not worth worrying about because the alternatives are worse in terms of picture quality on 99% of the displays out there. Ifg you can see all the variation designed to be cvisibel towards white it doesn't matter where he white point is as long as :

A; its nice and bright looking and not limiting display precision( clipping)
B; it doesn't melt your eyeballs/face/sofa.

Most digital displays are inherently linear so they already LUT the actual incoming imagery to produce an end to end gamma compatable with video, quite a few manufacturers also play around with the LUT to improve the performance of the display at this point so its already sort of crudely profiled anyway.

So on some displays what you do is maximise the contrast without clipping and ignore grayscale.

Then you hope that your display has enough precision to minimise banding with that maximised contrast range when you profile it and generate a LUT to take care of gamma , grayscale and gamut. More contrast equals less banding and will hopefully stand up the Lutting process in the PC...savvy?

Luts: 2 types.

1dlut simple lut maps one number to another essentially gives you RGB correction which in turn gives you gamma and grayscale.

3dluts ( sometimes called cubes) a real modelled 3d colorspace transform: you can ead all the head bursting stuff on the net but the simple point is you can control Hue Saturation and Intensity as well as RGB. This gets you gamut control as well as gamma and grayscale..RGBHSI in other words...it can also do other things such as crosstalk but its really just a fancy term for manipulating HSI according to RGB levels as well as gamut.

Graphics cards generally can apply 1dLUTs in hardware ( apart from overlay which bypasses this in the hardware).

3dluts generally equire a software hook of some description to work properly with the application: photoshop for example will take an ICC profile and adjust for gamut. The same ICC profile will still operate in your graphics card but again you only get grayscale and gamma not gamut.

1dluts generally incurr no processing overhead because its a simple calculation handled by teh graphics card. 3dluts generally require cpu processing to some degree and incurr overhead.

Luts have their own precision 8bit, 10bit , 16bit, generally speaking 8bit is fine as your display is likely to be the limiting factor anyway and 10bit takes a huge amount of time to calculate (3dLUTs anway 1dLUTs by definition are pretty simple).

You might be able to apply a 3dLUT as a shader in the graphics card and get the graphics card to do all the calculating... my knowledge runs out here ...when people start talking about shaders I generally roll my eyes and claim ignorance of all things involving 3d pipelines.

LUTs are not magic and have to work within the limitations of a given display (no display is perfect). Luts will not for example turn a monochrome CRT into full color.

It is absolutely the BEST way to calibrate a display chain and generally speaking wo't do any remotely serious work on an uncalibrated display system:however I do get away with 1dLUT for 90% of my working time.

Why do we not have profiling systems for the home user?
Answer : the only people able to take advantage of it are HTPC users (assuming the software can use it) and owners of higher end standalone scalers that accept pre-generated LUts (hen's teeth).

So when do we get a profiler and LUT builder from CalMan ? :D

So when do we get a profiler and LUT builder from CalMan ? :D

I dunno, but I've got my fingers crossed.

Thanks for all the feedback.

Sounds like I should leave a well-enough calibrated display (non-Elite Kuro, so the LCD discussion doesn't apply) alone - especially since playback apps may not even use the ICC profile.

I have already spent some time wrangling with black levels and the best I could come up with is to expand video to 0-255 so that it gets recompressed to 16-235 for HDMI compliance. This is the only way to get the desktop (e.g. photos) to look right as well, but of course, BTB/WTW get clipped.

Thanks for the suggestion to check 10% steps, I didn't realize that could get hosed by the PC just spitting out native RGB (my display's gamma is as close to flat as I can get it, as calibrated by standalone player).


Once you get the black levels dialed in on the PC, updating the video card LUT to work as a video equalizer to nail your gamma and white point can be done, but currently their isn't any software designed for HTPC use that does that.

You mean none besides yours? ;)

I dunno, but I've got my fingers crossed.

Maybe if it doesn't show up in CalMAN, it can show up here again.... :p

apologies for typos , wireless keyboard is a bit laggy

I do get some use from the gamma slider on my graphics card but be careful.

apologies for typos , wireless keyboard is a bit laggy

Whew! I'll say :D