Colour output question

[pijetro]

Good day.....
I've got an question about output of both DVD and BluRay players...
It's an RGB>YUV question.

Here goes my assumptions.

DVD's are inherently encoded to a format that's got YUV colourspace..
I assume BluRay (both Mpeg2 and H.264) are the same.

Newer LCD's and Plasma's are viewed via RGB colourspace..

Where does the YUV>RGB conversion usually take place?
Is it in the standalone, or in the HDTV set?
Does the same hold true for bluray settops?
Do the RGB cables carry YUV, or do they output RGB colour??

The reason i ask, is indirect.
All my colour monitoring with my NLE is done with YUV to an interlaced display (YUV obviously). I'm just wondering if it's worth taking the plunge, and spending larger amounts of money monitoring on an RGB display for my HDV content.

How does this all tie into 609 and 709 colour profiles?

Sorry for all the questions..

[edDV]

Good day.....
I've got an question about output of both DVD and BluRay players...
It's an RGB>YUV question.

Here goes my assumptions.

DVD's are inherently encoded to a format that's got YUV colourspace..
I assume BluRay (both Mpeg2 and H.264) are the same.

Newer LCD's and Plasma's are viewed via RGB colourspace..

Where does the YUV>RGB conversion usually take place?

Is it in the standalone, or in the HDTV set?
Does the same hold true for bluray settops?
Do the RGB cables carry YUV, or do they output RGB colour??

I'll answer in part since near evening meal time here.

RGB vs YCbCr feed request is part of the HDCP handshake negotiation. If the monitor wants RGB, the conversion is done on the display card. The HDMI spec supports RGB or YCbCr.

Some capture devices, like Black Magic Intensity, only support YCbCr. In those cases, the display device must make the conversion to RGB.

I'm not sure what happens if the display won't accept YCbCr. I think they must per spec.

Back later.

[pijetro]

Thanks for the reply edDV..

My question is based on the assumption that all LCD and plasmas are displayed in RGB..
If in the future, if i'm editing on a proper HD monitor, i will need to feed it RGB, and not a YUV signal. This will determine where my money might need to be spent.

But for now anyways, as far as i'm concerned, my pipeline is YUV all the way through my interlaced SD broadcast monitor. My Matrox RT.X2 card will be going the way of the dodo in the next year or so.

I just wanted to straighten out the DVD/BluRay assumptions.
Since DVI is an 8 bit RGB, and since HDMI carry both YUV and RGB, i'm starting to wonder if some DVD/BluRay players have RGB conversion internally.
And if the signal comes to the HDTV as YUV, at that point, the TV set will do the conversion via chip.

Just a guess..
Enjoy dinner

[jagabo]

But for now anyways, as far as i'm concerned, my pipeline is YUV all the way through my interlaced SD broadcast monitor.

It's RGB on the face of the CRT.

i'm starting to wonder if some DVD/BluRay players have RGB conversion internally.

They all have it. If the TV wants RGB they have to supply it. At least some allow you to force the colorspace. My WDTV Live can be set to YUV, RGB Low, or RGB High (one is REC scaling the other PC, I forget which is which).

And if the signal comes to the HDTV as YUV, at that point, the TV set will do the conversion via chip.

Of course.

[pijetro]

Thank you...

So reasonable deduction tells me that all hardware needs to be ready for the conversion..Whether at the front end or the back end..
What a shame...
Spend several thousand on monitor for colour correcting, just to have the blacks crushed, or oversaturated, because of a 30 cent chip in the LCD....

Thanks to everybody for their help...

[edDV]

Thank you...

So reasonable deduction tells me that all hardware needs to be ready for the conversion..Whether at the front end or the back end..
What a shame...
Spend several thousand on monitor for colour correcting, just to have the blacks crushed, or oversaturated, because of a 30 cent chip in the LCD....

Thanks to everybody for their help...

That "shouldn't" be happening for a properly calibrated display. The first step in color correction is to verify the display is showing correct levels when presented with standard test signals (e.g. SMPTE color bar or THX optimizer*). Ideally this would come from a test signal generator because computers can't be trusted to produce correct levels via display cards. Likewise, DVD/Blu-Ray/media players can't be trusted until verified.

In my experience, the most trusted calibration path through my computers has been IEEE-1394 (Firewire) through a DV editor with scopes (e.g. FCP, Premiere, Vegas). I first use the analog color bar output of a Canopus ADVC-100 to adjust the monitor. Then I compare the digital IEEE-1394 path from a standard color bar on the timeline through the ADVC (7.5 IRE setup mode**) to the TV's S-Video input.

Then I compare the analog component and HDMI/DVI digital paths from editor timeline, through the display card to the display. If the levels don't match, then levels must be adjusted in the display card software so that levels match through IEEE-1394/S-Video, analog component and DVI/HDMI at the display.

Next I burn a DVD from the timeline with SMPTE bars plus other test signals. The DVD is used to verify levels coming out of the various DVD/Blu-Ray/media players when played directly to the display via analog component or HDMI. Ideally everything will match at the display but in practice, the various players will differ in black, white and chroma saturation. When that happens, the player should be adjusted if possible, or monitor setting corrections should be noted for each input. It helps if the display allows separate level presets per input.

When all is set properly, a SMPTE color bar will display with proper levels from all players and through the computer's analog and digital paths. The level's shown on the editor scopes should match the display. Only then is the system ready for color correction of input video.


* The THX optimizer or other test signals like the Bell Nuit HD testchart can be used for fine adjustment.
http://www.belle-nuit.com/testchart.html

** PAL systems would use the 0.0 IRE setting.

[edDV]

...
The reason i ask, is indirect.
All my colour monitoring with my NLE is done with YUV to an interlaced display (YUV obviously). I'm just wondering if it's worth taking the plunge, and spending larger amounts of money monitoring on an RGB display for my HDV content.

How does this all tie into 609 and 709 colour profiles?

The above is mostly about setting luminance black and white levels correctly. Secondary adjustments such as gamma and linearity are usually internal service technician adjustments best done in a service shop with access to sophisticated test equipment.

User chroma adjustments are usually limited to chroma saturation and tint/hue. Consumer HDTV sets don't give user access to Rec.601 vs Rec.709 settings. Instead there is an assumption that Rec.601 chroma levels will be used for SD resolutions and Rec.709 for 720p, 1080i and 1080p. Lower price HDTV sets may lack switchable color space. This becomes an issue when downsizing HD source to SD DVD 720x480. You may choose to do a color correction after downscale.

All HD displays convert YCbCr input to RGB internally. If by "RGB display" you mean RGB over HDMI, then you force the color space conversion back on the display card which may be less precise.

FYI - camcorders with HDMI outputs export as YCbCr.

[jagabo]

And analog component, composite, and s-video are always YUV. Analog VGA is RGB.