[ev666il]

Recently I've been questioning about the opportuneness of calibrating my 9G Kuro to both the rec709 and PAL/SECAM standards, assigning ISF-DAY to the former and ISF-NIGHT to the latter.


I'm having my BD player perform Color Space Upconversion by setting "HDMI Color space" to "YCbCr 4:4:4" and I was wondering whether this also implied upsampling SD color space from regular DVDs to rec709. If this was the case, then I shouldn't probably waste my time trying to calibrate my Kuro to the PAL/SECAM standard.


Could anyone shed some light on the matter?

 

[Mr.D]

If the source is outputting 1080 then it should ideally be matrixing using rec.709 regardless of whether the source material is SD or HD. Whether it is or not is a different matter.


Assume rec.709 and see what the visual results are , you need to do some investigating and make a decision from there.

 

[Kevin McCarthy]

Mr. D: Your reply appears to answer a question I was wrestling with. I just purchased a VideoEQ Pro CMS, and was planning to use it to calibrate my Oppo BPD-83 source + JVC RS15 projector. I was under what now appears to be a miss-impression that I would need two custom LUTs, one to bring DVD material to SMPTE-C, and another to bring Blu-ray material to Rec 709, but since the Oppo is set to upconvert any SD material to 1080P, it now appears that a single custom setting in the CMS to meet Rec 709 is all that is in order. Could you please confirm this? Thanks


Kevin

 

[PlasmaPZ80U]

I also have a similar question as the OP. I'm using a PS3 on a Samsung B650 LCD TV and have calibrated the CMS to Rec. 709, not Rec. 601. I mostly watch BDs, but also watch some DVDs, which my PS3 outputs at 1080p. Does the PS3 upconvert the Rec. 601 colorspace to Rec. 709, basically correcting for the fact a Rec. 601 source is being played back on a display calibrated to Rec. 709?

 

[Mr.D]



Quote:
Originally Posted by Kevin McCarthy /forum/post/18181796


Mr. D: Your reply appears to answer a question I was wrestling with. I just purchased a VideoEQ Pro CMS, and was planning to use it to calibrate my Oppo BPD-83 source + JVC RS15 projector. I was under what now appears to be a miss-impression that I would need two custom LUTs, one to bring DVD material to SMPTE-C, and another to bring Blu-ray material to Rec 709, but since the Oppo is set to upconvert any SD material to 1080P, it now appears that a single custom setting in the CMS to meet Rec 709 is all that is in order. Could you please confirm this? Thanks


Kevin

If the SD is going through the consistent rec.709 matrixing when its upscaled then you should be fine with the one setting. It all depends on what the source is doing.


There are a few things that can confuse the issue. Does the player do the upscaling in an intermediate RGB stage rather than staying in YCbCr for example then convert back to YCbCr 4:4:4 for example.


Ideally anything that gets output as 1080p regardless of origination (ie SD DVD) should be correctly twisted back into rec.709. If its not then you may have to have two settings but at that point its anyones guess as to ho wthe material has been handled if its not actually re.709 , its probably not SMPTE either by that stage...probably just some sort of "fudge".


Use the same patterns from HD and SD sources and see what you get. Unlikley any slight differences in mastering will be larger than SMPTE vs rec.709.

 

[TomHuffman]



Quote:
Originally Posted by Kevin McCarthy /forum/post/18181796


I was under what now appears to be a miss-impression that I would need two custom LUTs, one to bring DVD material to SMPTE-C, and another to bring Blu-ray material to Rec 709, but since the Oppo is set to upconvert any SD material to 1080P, it now appears that a single custom setting in the CMS to meet Rec 709 is all that is in order. Could you please confirm this?

There are two entirely separate issues that are being conflated here.

1. Having the proper color decoding applied to the source material.

2. Calibrating a display using an external device to use different gamuts.


Since your Oppo is upconverting SD material to 1080P, that means your display will not have to do any scaling or deinterlacing and if the Oppo works correctly, it will also do the YCbCr-to-RGB conversion using Rec. 601 coefficients. However, neither of these issues has any effect on the gamut in which the material will be displayed. If you want to display DVD content in a SMPTE-C gamut, then you'll have to use the processor to alter the natural gamut of your display.


The same is true of Blu-ray. The Oppo should use Rec. 709 color decoding coefficients, but you would still have to calibrate your display's gamut to match the Rec. 709 standard.

 

[HDTVChallenged]



Quote:
Originally Posted by TomHuffman /forum/post/18182816


The same is true of Blu-ray. The Oppo should use Rec. 709 color decoding coefficients, but you would still have to calibrate your display's gamut to match the Rec. 709 standard.

Of course, the visual difference between SMPTE-C and 709 display gamut will be undetectable, except to a colorimeter/spectro.


Then again, I use a cheap RF attenuator on the Blue channel to help bend 709 to quasi-601 for my ancient 709-challenged "HDTV Ready" RPTV. So I guess, I'm not all that picky about hitting the absolute CIE xy coordinates.

 

[ChrisWiggles]



Quote:
Originally Posted by HDTVChallenged /forum/post/18183116


Of course, the visual difference between SMPTE-C and 709 display gamut will be undetectable, except to a colorimeter/spectro.

I would not agree with this. It may not be very significant for an average viewer, but to a critical viewer it's not an insignificant difference, even if it may seem subtle. But it certainly is not visually undetectable.

 

[HDTVChallenged]



Quote:
Originally Posted by ChrisWiggles /forum/post/18183152


I would not agree with this. It may not be very significant for an average viewer, but to a critical viewer it's not an insignificant difference, even if it may seem subtle. But it certainly is not visually undetectable.

I'm moderately critical ... but yet I can't tell the difference between my quasi-SMPTE-C-phosphor HDTV and my CRT computer monitor (which measures "considerably" different from either 709, 601 or SMPTE-C) ... unless they are side-by-side.


I'm not talking about the de-matrixing (601 vs. 709, which will make a difference.) I'm talking about the actual physical gamut. There's just not enough distance from SMPTE-C to 709 to be visually significant as long as everything else is lined up to fit whatever gamut the display has. Absent a visual reference, it'll look "right" to the viewer, even if it isn't exact.

 

[ChrisWiggles]



Quote:
Originally Posted by HDTVChallenged /forum/post/18183302


I'm moderately critical ... but yet I can't tell the difference between my quasi-SMPTE-C-phosphor HDTV and my CRT computer monitor (which measures "considerably" different from either 709, 601 or SMPTE-C) ... unless they are side-by-side.


I'm not talking about the de-matrixing (601 vs. 709, which will make a difference.) I'm talking about the actual physical gamut. There's just not enough distance from SMPTE-C to 709 to be visually significant as long as everything else is lined up to fit whatever gamut the display has. Absent a visual reference, it'll look "right" to the viewer, even if it isn't exact.

As am I. The physical gamut difference between SMPTE C and 709 is subtle, but easily visible if you know. I have a memory for each gamut on my display and it's very easy to see the difference as you switch between them. It isn't the end of the world, but it definitely has a visual impact, particularly on heavily saturated reds and also on skintones. Many viewers wouldn't care, and many displays have gamuts far worse than the difference between the two, but it is a visible difference for sure.

 

[Kevin McCarthy]

Tom: I have a lot of respect for you, and your conflation detection is almost certainly correct; the problem is that I'm having trouble following your response. I suppose that this what happens when CMS's become affordable enough for dilettantes to get in the game. My situation is that I have an Oppo BDP-83, a VideoEQ Pro, and an RS15. The Oppo upscales everything to 1080P (24 for film sources). We watch both SD and Blu-ray disks, and I would like to use the VEQ to correct the display's oversaturated color gamut (I'll also be correcting the greyscale and gamma, but I think that I have those down). I'll be using the AVS HD 709 color windows, and want to know what my target(s) should be. Would it be enough to just get the primaries and secondaries' x,y,Y to match the Rec 709 specs, or do I need to have a different correction, depending on whether the disk is SD or HD? Or is even this simple dichotomy flawed? FWIW, I have for reasons I marginally understand (that's how it is stored on the disks?) chosen to force the Oppo to output in the 4:2:2 color space and the RS15 to expect this.


Some simple "Do this:" advice would be welcome, and hopefully the above doesn't merit Pauli's scathing "That... that is not even wrong!!".


If getting me up to speed will take more than a few minutes, I'd be happy to cover it.


Kevin

 

[TomHuffman]



Quote:
Originally Posted by Kevin McCarthy /forum/post/18185959


My situation is that I have an Oppo BDP-83, a VideoEQ Pro, and an RS15. The Oppo upscales everything to 1080P (24 for film sources). We watch both SD and Blu-ray disks, and I would like to use the VEQ to correct the display's oversaturated color gamut (I'll also be correcting the greyscale and gamma, but I think that I have those down). I'll be using the AVS HD 709 color windows, and want to know what my target(s) should be. Would it be enough to just get the primaries and secondaries' x,y,Y to match the Rec 709 specs, or do I need to have a different correction, depending on whether the disk is SD or HD? Or is even this simple dichotomy flawed? FWIW, I have for reasons I marginally understand (that's how it is stored on the disks?) chosen to force the Oppo to output in the 4:2:2 color space and the RS15 to expect this.

Any set of test patterns is fine--for gamut purposes all discs are the same. Hit the xyY targets and you have calibrated the display to Rec. 709.


The data on the disc is stored in YCbCr format (4:2:2 just specifies the degree of subsampling that's being used--DVD and Blu-ray use 4:2:0, but that's not something you need to concern yourself with). At some point prior to display, the data on the disc has to be converted to RGB. If a player uses proper color decoding coefficients, then output RGB. If it doesn't, then output YCbCr and have the display do the color decoding. In all likelihood, either would be fine.


The point I was making before is that all of these color decoding issues are not directly related to the task of calibrating to a specific gamut.

 

[PlasmaPZ80U]



Quote:
Originally Posted by PlasmaPZ80U /forum/post/18182579


I also have a similar question as the OP. I'm using a PS3 on a Samsung B650 LCD TV and have calibrated the CMS to Rec. 709, not Rec. 601. I mostly watch BDs, but also watch some DVDs, which my PS3 outputs at 1080p. Does the PS3 upconvert the Rec. 601 colorspace to Rec. 709, basically correcting for the fact a Rec. 601 source is being played back on a display calibrated to Rec. 709?

Bump. Does the PS3 properly upconvert the colorspace to Rec. 709 when playing DVDs at 1080p?

 

[Kevin McCarthy]

Thanks, Tom!

 

[thomasl]



Quote:
Originally Posted by Kevin McCarthy /forum/post/18185959


My situation is that I have an Oppo BDP-83, a VideoEQ Pro, and an RS15. The Oppo upscales everything to 1080P (24 for film sources).

Kevin,


I'll just add that the Oppo does the necessary matrix conversions/twisting correctly when processing Rec. 601 material (SD DVDs) and outputting it in a HD format (1080p) so you should be fine outputting YCbCr to your display (this assumes that your display properly decodes all HD formats sent to it using Rec. 709).


cheers,



--tom

 

[TomHuffman]



Quote:
Originally Posted by PlasmaPZ80U /forum/post/18186398


Bump. Does the PS3 properly upconvert the colorspace to Rec. 709 when playing DVDs at 1080p?

To to be clear, Rec. 709 is both a gamut and a specification for color decoding. SMPTE-C, on the other hand, is just a gamut, though the Rec. 601 color decoding specification is implicit. Ordinarily, "upconvert" refers just to the scaling of SD (720x480) up to HD (1920x1080). This isn't directly related to either color decoding or the displayed gamut. An HD signal can be displayed in a SMPTE-C gamut or a Rec. 709 gamut. However, if it is upconverted from a DVD source, the player should use Rec. 601 color decoding.


As to the question of whether the PS3 specifically does this or not, I honestly don't know.

 

[HDTVChallenged]



Quote:
Originally Posted by TomHuffman /forum/post/18187135


As to the question of whether the PS3 specifically does this or not, I honestly don't know.

Easy enough to check. Just pop in your old AVIA or VE DVD and check the SMPTE Color bar chart or Bars w/ grey reference.

 

[Mr.D]

The Bellenuit test pattern also has a section fro checking 709 or 601 rematrixing. I have not used it in this capacity but can confirm the pattern is accurate in most other regards.

 

[PlasmaPZ80U]

I only have the AVSHD709 Disc. In any case, what should I be looking for in terms of test patterns? Would I need to use my meter or blue only mode in the process?


Also, if the PS3 is doing what it should, does this mean I won't need to have a second calibration optimized for a SMPTE-C gamut with Rec. 601 color decoding?


As it stands now, I have calibrated the xyY of my primaries and secondaries to Rec. 709 standards (or more accurately, to a custom gamut that is very close to Rec. 709 primaries). I'm currently using this calibration for both 1080p BDs and 1080p upconverted DVDs.

 

[HDTVChallenged]



Quote:
Originally Posted by PlasmaPZ80U /forum/post/18189513


I only have the AVSHD709 Disc. In any case, what should I be looking for in terms of test patterns? Would I need to use my meter or blue only mode in the process?

That would complicate the matter. You'll need a known 601 encoded pattern. The color bars with 75% gray is the best choice.

Quote:
Also, if the PS3 is doing what it should, does this mean I won't need to have a second calibration optimized for a SMPTE-C gamut with Rec. 601 color decoding?

Yes/No.


What you need to do to confirm that the PS3 is twisting 601 to 709 properly is:


1) Forget about the physical display gamut for now.


2) Put up your 709 color bar pattern (preferably from a Blu-ray source) and adjust your display's color/tint etc...


3) Then put up your 601 DVD pattern. If the PS3 is doing its 601->709 twisting properly, then you should *not* have to make any further color/tint adjustments to make the 601 pattern look right.


4) The R,G,B color filter method should suffice. The biggest difference between 601 and 709 will be apparent in the blue channel.


I'd check all this for you, but as I don't have an HDMI display, it's a bit of a moot point for me. I suspect that it does works correctly, but I can't confirm it directly.


As Tom said above, calibrating the physical gamut of your display is a different issue than the matrix twist from 601 to 709.


PS: The Godfather of Standards and Calibrations, aka. Joe Kane, does not consider the difference between the SMPTE-C and "Rec 709" chromaticity/display gamut to be a significant issue.