Setting HD Color Space with SD Disc RGBCYM Windows? - AVS Forum
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post #1 of 5 Old 01-25-2012, 04:07 AM - Thread Starter
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A discussion in another forum got me wondering about the difference between the windowed greyscale and gamut patterns on SD and HD calibration discs. My basic understanding is that gamut information isn't recorded on a disc or present anywhere in the video signal, which is partly why we have to calibrate our display's gamuts in the first place.

If my understanding is correct (which I readily admit it could be incorrect) could one hypothetically use the RGBCYM window patterns from an SD test disc, set their calibration software to the REC 709 targets, and then calibrate an HD display? I.e., if you have a fully saturated green pattern on a test disc, and you tell your calibration software that you want that fully saturated green window to match the REC 709 green target, you could properly set green despite only using an "SD" test disc.

Am I missing something or would this actually work? I'm not personally going to try this, but the person in the other forum only gets their HD material from cable, only owns a DVD player, but wants to set his display to REC 709. Several of us suggested other ways of doing this - including running the free HD test disc mp4 from his laptop and connecting that to his display - but it got some of us wondering about this a little more in depth.

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post #2 of 5 Old 01-25-2012, 04:57 AM
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Check the last 2 or 3 days of posts in the Chromapure thread. Tom addressed this issue.
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post #3 of 5 Old 01-25-2012, 05:04 AM - Thread Starter
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Quote:
Originally Posted by dsinger View Post

Check the last 2 or 3 days of posts in the Chromapure thread. Tom addressed this issue.

Thanks!

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post #4 of 5 Old 01-25-2012, 05:14 AM
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He did and partly in reply to my question about it.

My stepdad wants his RPTV calibrated but I know his blu ray player doesn't playback AVS709 so I'm tempted to use a DVD of test patterns.

There's still things I don't understand though when it comes to this.

Someone was saying they are concerned with preserving the 601 color space for upconverted DVDs when played back using a Blu Ray player.

All very confusing and fascinating.

-Brian
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post #5 of 5 Old 01-25-2012, 08:19 AM - Thread Starter
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Quote:
Originally Posted by Brian Hampton View Post

He did and partly in reply to my question about it.

My stepdad wants his RPTV calibrated but I know his blu ray player doesn't playback AVS709 so I'm tempted to use a DVD of test patterns.

There's still things I don't understand though when it comes to this.

Someone was saying they are concerned with preserving the 601 color space for upconverted DVDs when played back using a Blu Ray player.

All very confusing and fascinating.

-Brian

My basic understanding of what Tom wrote is this:

When SD material is mastered, the people doing the mastering most likely have their displays calibrated to SMPTE-C gamut standards. Likewise, when HD is mastered the people doing the mastering should have their displays calibrated to REC709 (whether this is actually the case universally has been extensively debated in other threads). Either way, in order to transfer the finished product to a disc, it must be encoded from RGB to Y/Cb/Cr, and the coefficients used to do this actually differ depending on whether the material was mastered in SMPTE-C or REC709.

When the material is decoded in a player, the player needs to use the correct coefficients in going from Y/Cb/Cr to RGB in order to avoid any color decoding errors. This is why some players have a setting for colorspace where you can select either SD (SMPTE-C, REC601, or whatever they call the setting), HD (REC709), or Auto. Players that don't have this option should automatically pick, or improperly only use one set of coefficients. Once the material is decoded back into RGB information, it doesn't matter whether you're calibrating your gamut to SMPTE-C, REC709, or any other gamut - that is simply determined by the targets that you set in your calibration program.

Clear as mud?

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