Calibration disc for SD?

Originally Posted by cmcfalls

I recently purchased an LCD TV and have heard a lot about getting it calibrated. I know the best option is to have it professionally calibrated, but I don't think my wife will go for that.

So, I intended to use a disc for the calibration. But, I also do not have Blu Ray or HD-DVD player. So, I will be using a standard DVD player.

Can I use the Avia disc in standard DVD player? I am pretty sure the DVE disc will, but what about Avia?

Also, what about using the free AVS DVD ones located here? They are both in HD-DVD and Blu Ray, but is there a standard DVD one I can use?

I plan on upgrading to a Blu Ray or HD-DVD player in the future, but right now all I have is an Xbox 360 and don't want to wait to calibrate it. Thanks!

2. A standard dvd player and a standard disk can be used to calibrate a HD LCD...the one fly in the ointment is that you are assuming that the LCD's video processor is properly converting SMPTE-C colot gamut (i.e. SD) to the REC 709 color gamut (i.e. HD). As such an HD-DVD player or Blu-Ray player with HD test disks would be better.

Originally Posted by John Ryder

I'd just use the free THX Optimizer that comes with many DVD"s these days...it should get your set looking good...better than the default settings for sure..

I wouldn't invest money in getting an LCD professionally calibrated unless you are an uber perfectionist.

Originally Posted by ChrisWiggles

There is not correct, there is no twist of gamut. There is a twist of the component video matrix between 601 and 709. There is no ability to affect any change between SMPTE C and 709 gamut, this is physical to the display device itself and what its primaries are. These are easily confused because they both deal with color, but they are quite distinct. Also, you are making the very significant assumption of an upscaling DVD player that is outputting component video (digital or analog). It sounds like the poster was just asking about a "standard" DVD player, which I think it is safe to assume means just a 480i/480p DVD player, not one that upscales. If there is no upscaling that crosses the SD/HD threshold, there is no need for a twist of colorspace (and also again assuming component video, if it's RGB out it's a moot point).

Originally Posted by hwjohn

It is possible to "re-map" or "twist" (whatever you want to call it) the 709 gamut to SMPTE-C. Whether a player actually does it or not is a different question. Bear5k has discussed this pretty extensively.

Originally Posted by ChrisWiggles

There is not correct, there is no twist of gamut. There is a twist of the component video matrix between 601 and 709. There is no ability to affect any change between SMPTE C and 709 gamut, this is physical to the display device itself and what its primaries are. These are easily confused because they both deal with color, but they are quite distinct. Also, you are making the very significant assumption of an upscaling DVD player that is outputting component video (digital or analog). It sounds like the poster was just asking about a "standard" DVD player, which I think it is safe to assume means just a 480i/480p DVD player, not one that upscales. If there is no upscaling that crosses the SD/HD threshold, there is no need for a twist of colorspace (and also again assuming component video, if it's RGB out it's a moot point).

Originally Posted by hwjohn

It is possible to "re-map" or "twist" (whatever you want to call it) the 709 gamut to SMPTE-C. Whether a player actually does it or not is a different question. Bear5k has discussed this pretty extensively.

Originally Posted by Joelc

Chris:

Although you are correct that I did simplify things in that I

(i) assumed the DVD player would be outputting YCbCr
(ii) assumed that the SD primaries would be mapped to HD primaries and
(iii) assumed that the display's gamut was REC 709 I do respectfully -- and I do mean respectfully -- disagree with you...

And here is why:

-- Yes, the display primaries are either SMPTE-C or REC 709 and calibration can not change that...they are what they are!

-- A SD signal at some point must be converted to a HD signal to be dispalyed on a HD device (and this will occur in the display since the OP is using a SD DVD plater)...so, the point is that to the extent that SMPTE-C red is mapped to REC 709 red (i.e. because I am assuming that the display's color gamut is REC 709 and that the RGB triplet rather than the RGB rendering intent is being preserved) then a SD test disk in a SD DVD player can be used to calibrate a REC 709 color gamut display..

Are we closer to agreeing?

-- A SD signal at some point must be converted to a HD signal to be dispalyed on a HD device (and this will occur in the display since the OP is using a SD DVD plater)...so, the point is that to the extent that SMPTE-C red is mapped to REC 709 red

Quote:
Originally Posted by Kris Deering
"Hey Greg

I think people here are still having trouble differentiating between color decoding and color primary position. They are two seperate animals but easy to get confused in general conversation. "

endquote

Gregr:
Yes, I agree. It's been confused several times above. But I'm having trouble figuring out how to explain the difference and be more clear.

Color decoding is how signals are converted from YCbCr to RGB, color encoding is how signals are converted from RGB to YCbCr. All projectors with analog YPbPr or digital YCbCr inputs must have the ability to switch between Rec 601 and Rec 709 color decoding in order to be compatible with both standard-definition and high-definition input signals. Some projectors (not all) allow the user to manually select which standard is used for color decoding. Sometimes they call that a Color Space selection, which is probably what confuses a lot of people.

SMPTE-C primaries or Rec. 709 primaries refer to the desired color of the red, green, and blue primaries used by the projector. In today's projectors the actual (native) colors of the red and green primaries are almost always more saturated than the colors defined by either of those standards. In many cases, there is nothing the user can do about that in the projector (although an external CMS - what Joel is doing - may be used). If the primaries are wrong, the colors produced by the projector will be wrong (although some people prefer that the primaries are wrong - that is a different issue). But in some projectors an electronic Color Management System (CMS) is provided, which allows the video signals to be modified so that 100% red, green, and blue signals produce colors (virtual primaries) different than the native primaries of the projector. In that case, the CMS can sometimes be used to calibrate the virtual primaries so that they are at (or close to) the location of the SMPTE-C and Rec. 709 primaries. i.e. a virtual color gamut is created electronically that can be made to match the standards. In that case, if the CMS is designed correctly, all of the colors within the virtual color gamut are modified to match the standards, and the projector can produce accurate colors.

The Marantz was cited earlier as having this ability - it does not. The InFocus was also cited as having this ability - I haven't seen one of those in a while but earlier versions did not have this ability. The Sharp XV-Z projectors have such a CMS, as did the Yamaha projectors I mentioned earlier. I've been told the Samsung projector mentioned by Chris had the ability to be calibrated in this way, but I don't know what user adjustments it had. Not all projectors that advertise or claim a CMS system have the ability to be calibrated correctly to the standards because they may lack the ability to make all of the necessary independent adjustments. i.e. just because a projector allows you to change its primary (or other) colors doesn't mean it allows you to do it correctly to match (or get close to) the standards. Some of the Sony projectors have a Wide and Normal color space mode. In the VPL-VW60 the Normal mode is relatively close to the SMPTE-C primaries, but it wasn't in previous Sony projectors that had Wide and Normal modes.
__________________
Greg Rogers
AccuPel
Widescreen Review

Originally Posted by ChrisWiggles

No, the player does not do this. Some displays have CMS capabilities that allow you to adjust the effective primaries within the boundaries of the maximum physical gamut, though most do not. The matrix twist has no bearing on the display gamut whatsoever and only involves accurate color encode/decode flow. Whenever a "twist" is described, it most certainly refers to the component video colorspace and not to gamut, as it is describing the location and relationship of the component video cube to the RGB unit cube and its angle.

Are you saying it is impossible for a player to re-map the gamut? Or are you saying that no player that you know of actually does it?

I understand (and I'm pretty sure Joelc does too, but he can speak for himself) that color decoding and primaries are two completely different issues. However, the SMPTE-C gamut lies within the Rec 709 gamut, so it is possible for the player to alter the component (or RGB signals) so that a display with Rec 709 primaries would "preserve rendering intent" as Bear5k puts it.

In order to see the correct red using Rec 709 primaries, the player could "re-map" the RGB triplet to something <235,>16,>16, which would correspond to SMPTE-C "red" within the Rec 709 gamut.

How are we doing so far...and, hoping that we are in agreement...

what should happen in the twist...in other words, should the twist preserve the originally encoded RGB triplet (i.e. SMPTE-C red is twisted and decoded to REC 709 red) or preserve the originally encoded rendering intent (i.e. SMPTE-C red is twisted such that when it is decoded using a REC algorithm matrix it is inside the larger REC 709 gamut)...

Originally Posted by ChrisWiggles

Points 1-4 are all correct.



Absolutely the goal is to have the correct RGB triplet. That's the whole point of accurate color decoding, otherwise you have the wrong colors. Dealing with gamut should be done with a fully featured CMS system or something capable of dealing with such processing such as the lumagen, etc. I am not aware of any player out there that at all has this capability, and I would strongly disagree with a fixed gamut compensation that assumes accurate 709. The radiance doesn't, it is a user adjusted to compensate for oversaturated display to achieve the desired gamut.

I absolutely agree that accurate gamut is important, however, it is NOT at all involved in the matrix twist which is a very simple operation and should be performed in a source device if it is crossing the SD/HD threshold and outputting component video. Furthermore, displays should have the ability to manually choose the decode matrix to allow for correct decoding in cases where the source device does not perform a matrix twist.

My major problem is that many people mistakenly think that the source device is performing a twist to compensate for the difference in primary chromaticity between SD and HD. This is absolutely not true, the twist is a compensation for the different component video matrices, and the gamut difference is altogether distinct. Changing the gamut is not a twist at all.

Originally Posted by ChrisWiggles

Points 1-4 are all correct.



Absolutely the goal is to have the correct RGB triplet. That's the whole point of accurate color decoding, otherwise you have the wrong colors. Dealing with gamut should be done with a fully featured CMS system or something capable of dealing with such processing such as the lumagen, etc. I am not aware of any player out there that at all has this capability, and I would strongly disagree with a fixed gamut compensation that assumes accurate 709. The radiance doesn't, it is a user adjusted to compensate for oversaturated display to achieve the desired gamut.

I absolutely agree that accurate gamut is important, however, it is NOT at all involved in the matrix twist which is a very simple operation and should be performed in a source device if it is crossing the SD/HD threshold and outputting component video. Furthermore, displays should have the ability to manually choose the decode matrix to allow for correct decoding in cases where the source device does not perform a matrix twist.

My major problem is that many people mistakenly think that the source device is performing a twist to compensate for the difference in primary chromaticity between SD and HD. This is absolutely not true, the twist is a compensation for the different component video matrices, and the gamut difference is altogether distinct. Changing the gamut is not a twist at all.

I don't know if there is any equipment out there that currently does such a remap.

I just wanted to make the point that it is possible (and desirable) if you can do it properly.

The whole situation would be made easier if all TVs had accurate primaries, which is what enthusiasts should push for from manufacturers.

Originally Posted by ChrisWiggles


True, but accurate to what? SMPTE C? 709? And given that most HD content is still being mastered on SMPTE C displays anyway the same as SD, it's kind of just a guess anyway as to what it's supposed to be.

Originally Posted by Joelc

Based on your above copmments that ....most HD content is still being mastered on SMPTE C display anyway... is it not the case that I should therefore use my Lumagen Radiance XD to calibrate the primaries and secondaries to match the SMPTE-C colour gamut?

If yes then great and no additional explanation is needed...if not then please explain why not.

Originally Posted by TomHuffman

Joel:

Let me jump in here. I have recently started calibrating my display to both SMPTE-C and Rec. 709. I found that some HD material looks better with the display calibrated to SMPTE-C primaries (primarily broadcast cable) and other material looks better calibrated to Rec. 709 primaries (primarily Blu-ray/HD DVD content), although there are exceptions to each.

In your particular case, your display's native gamut seems to be SMPTE-C in any case, so I would just calibrate to that and call it a day. If at some point in the future you get a display with a larger gamut, you can calibrate to both and use whichever one suits for given content.

Originally Posted by ChrisWiggles

True, but accurate to what? SMPTE C? 709? And given that most HD content is still being mastered on SMPTE C displays anyway the same as SD, it's kind of just a guess anyway as to what it's supposed to be.

Originally Posted by ChrisWiggles

True, but accurate to what? SMPTE C? 709? And given that most HD content is still being mastered on SMPTE C displays anyway the same as SD, it's kind of just a guess anyway as to what it's supposed to be.

On the other hand, the encode difference is very significant, very visible when it's done wrong. It is mathematically unambiguous to get the right returned RGB values.

Originally Posted by Joelc

Understood...I am/was curious as to whether one would consistently be better than the other as:

1. It is somewhat of a PITA to calibrate a projector to both colour gamuts even using a Lumagen RadianceXD; and

2. It requires great care becuase -- and I stand to be corrected -- one would need to play with the YCbCr decode matrix to see whether REC 601 or REC 709 decoding is better.

Originally Posted by TomHuffman

From my experience, as I said SMPTE-C looks consistently better to my eyes on broadcast, though there are some shows that look better in Rec. 709. We are not talking a night-and-day difference, but it is visible.

Originally Posted by TomHuffman

Can't you calibrate two entirely separate profiles on the Lumagen and then just switch between them when you like? Yes, you have to take care to do the 2 calibrations correctly, but that was always the case. If you just calibrate to the proper respective xyY values for each color space using the Accupel or DVD reference, you'll be fine.