Calibrating for limited RGB range using Windows 7 over HDMI - AVS Forum
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post #1 of 7 Old 02-14-2013, 02:38 PM - Thread Starter
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So, I've just come across the charming information that calibrating an HDTV to REC.709 using a PC is fraught with dangers, viz:

1) HDMI drivers don't always send the limited RGB range despite it being mandated

2) Video playback software can play merry havoc in the same way

I'm hoping to cut through all the bull and ask for advice on how best to calibrate an HDTV for DVD and Blu-Ray using Windows 7 Home Premium such that I can be sure I'm send the most appropriate video information possible. Here's my specs:

1) MacBook Pro
2) Windows 7 Home Premium
3) Thunderbolt to HDMI adapter
4) HDMI cable
5) HCFR Colormeter software 3.0.4
6) X-Rite DTP-94 colorimeter
7) AVS's own HD 709 patterns in MP4 format

I use the MacBook Pro (1) running Windows 7 HP (2) to both send the patterns (7) to the HDTV using cables (3) and (4), and read back using colorimeter (6) and software (5).

Help?

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post #2 of 7 Old 02-19-2013, 10:53 AM
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I was wondering the same thing! Windows color management is complex, convoluted, and completely confusing lol.... is there a simple way to display the color information being output by a pc? Or any source for that matter? What if I was using my hdtv as a monitor for my pc to play games as well as watch BD? I assume pc games ouyput in RGBfull but what about BD content from pc source over hdmi? Is that the proper situation to calibrate to RGBfull? Is a modern hdtv even capable of output that?

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post #3 of 7 Old 02-19-2013, 12:24 PM - Thread Starter
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nodixe: the whole thing really is a bit of a minefield. Let's say your PC is connected to an HDTV using an HDMI port on the PC:

1) Apparently some HDMI drivers are incorrectly set-up to send full-range RGB instead of limited-range RGB, which is the standard for HDMI. This means your DVD or Blu-Ray (both of which use limited-range RGB) may not appear optimally on the HDTV.

2) If you send a PC game over a properly-functioning HDMI, that means its blacks and whites are being crushed, because PC games use full-range RGB.

3) I suppose it's also possible that some PCs automatically switch between sending full-range and limited-range RGB over HDMI. That'd be nice. But how do we know? Apparently the only way to tell is to know in advance what the image ought to look like.

4) Some video playback software apparently incorrectly sends full-range RGB instead of limited-range (or does other stuff maybe) when playing DVDs and Blu-Rays, so that's another thing to consider, as this will mess with your output.

So, in order to properly calibrate an HDTV from a PC we have to:

A) Make sure the pattern playback software is sending the images completely unchanged, and at the proper limited-range RGB

B) Make sure the connection between the PC and the HDTV is also sending the correct signal for what we want: limited-range for movie files, DVDs and Blu-Ray; full-range for games and at all other times.

There's probably something else. Input from those experienced with these matters would be really appreciated. At the very least, it would be great to have some way of determining exactly what is being sent by our PCs and received by the HDTV.

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post #4 of 7 Old 02-19-2013, 02:53 PM
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We use Laptops with HDMI very often for display calibration, and rarely have any issues.

To be honest, I can't remember the last time we had an issue...

Some simple checks to follow can be found here: http://www.lightillusion.com/data_tv_levels.html

There are a couple of simple way to check is levels are basically correct.
Clipping is obvious with test frames, as shown in the link above.

And with a decent probe check for no black lift.
With the TV on, but with no input signal measure the black level.
The send zero black to the TV from the source and re-measure.
There will likely be 'some; small variation, but not much, if all is correct.
If there is a mismatch the variation will be a lot greater.

And yes, you do need to make sure all Windows colour management is off.

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Hope this helps.

Steve
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post #5 of 7 Old 02-19-2013, 06:47 PM
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Thanks for the input. Now that I think about it I guess I should just test every variable with a meter as that's part of the llearning process....

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post #6 of 7 Old 02-20-2013, 12:10 PM - Thread Starter
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Thanks for the feedback and the link. I've now been able to confirm, thanks to information on the linked page:
Quote:
What is important to understand up-front is that all displays show black as 'black' and white as 'white. This means that regardless of the input signal, if it is correctly matched to the display's expected input, black and white will look the same.
I wasn't sure, until I read this, whether "16" should correspond to black or not. Now I know it should, and that the washed out appearance of my Satellite STB and TV Input is down to some flawed aspect of my calibration process.

Now I just have to determine which aspect. I suspect it may be Windows Media Player, but any advice in that respect would be appreciated.

Thank you.
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post #7 of 7 Old 02-21-2013, 12:54 AM
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Happy to have been of some help!

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With playback from a PC check the graphics card settings for 'Video' mode.
There should be a 16-235/0-255 setting.
This is separate the the main PC output (the desktop for example).

Steve

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