Have a JVC DLA-HX2 and am setting it up.

I am using the component video inputs from 720p and 1080p sources. May in future use HDMI (DVI-D).

In the settings, it has a 'decoder' setting with options like NTSC and HDTV (also PAL). Which do I use? Hard to compare, but they appear to only change black level, but I could be missing something.

Any thoughts?

db

Greetings

HD material usually is shot with a larger color gamut (aka Triangle) than SD material. Assigning a smaller color palette to something with more colors is not a good thing.

That't the theory anyway. The is significant nuance to this especially where your JVC is concerns.

Regards

So I should set it to HDTV????

Will a Blu-ray playyer, xbox, and/or Sat receiver (all HD units) map the color space from standard def material?

One of the innumerable "dirty little secrets" of the consumer video manufacturing industry is that often times little regard for maintaining color fidelity has been incorporated when designing equipment. Many devices built early in the ramp up to HD only used the rec 601 (SMPTE C) color matrix. Some still do today. Joe Kane Productions was one of the few who pointed this out.

As it stands, HD displays assume that any incoming 720P, 1080I, or 1080P signal sent to it from up-converting DVD players, cable boxes, satellite boxes, should be decoded using the rec 709 color matrix. Some displays allow the user to tell it which color matrix to use, independent of incoming resolution. If you know that the original SD program was mastered in rec 601, you could select that color matrix and see a more accurate image on the HD display. I know for sure that the JKP/Samsung 700, 710, 800 and new 800B 1080P projector allow this.

The difference may be considered by some to be subtle. However, when most folks are shown a side-by-side comparison, it's readily recognizable, not just measurable. Many manufacturers maintain the position that if most consumers don't notice the difference, and buy the gear anyway, what's the harm? Isn't the most important reality in life that people will buy it?

Best regards and beautiful pictures,
G. Alan Brown, President
CinemaQuest, Inc.

"Advancing the art and science of electronic imaging"

So it sounds like the JVC "HDTV" color space should be used with my HD components (directtv HD, xbox 360, Blu-ray) and I'll have to live with some color space mapping errors from standard def content now and again.

db

I don't own your model of projector. You tell me if it has switchable color matrices. Then the question remains whether it works correctly when it switches. If you don't have the option, every standard DVD or original analog TV program you watch, which would be up-converted to HD before reaching the projector, will likely have distorted color.

GeorgeAB - see option in original post below. When on component, I get the NTSC, HDTV and PAL options.

Have a JVC DLA-HX2 and am setting it up.

I am using the component video inputs from 720p and 1080p sources. May in future use HDMI (DVI-D).

In the settings, it has a 'decoder' setting with options like NTSC and HDTV (also PAL). Which do I use? Hard to compare, but they appear to only change black level, but I could be missing something.

Any thoughts?

db

Have a JVC DLA-HX2 and am setting it up.

I am using the component video inputs from 720p and 1080p sources. May in future use HDMI (DVI-D).

In the settings, it has a 'decoder' setting with options like NTSC and HDTV (also PAL). Which do I use? Hard to compare, but they appear to only change black level, but I could be missing something.

Any thoughts?

db

There are really 2 issues...

1) color matrix or color decoder

2) color space

Color Space is fairly easy to understand and most people "get" color space. The CIE chart with reference triangle and actual measured primary and secondary points is the most common and understandable "definition" of color space. Most everybody knows Standard Def and High Def have different color spaces. Many people don't understand that ITU Rec 601 does not define ANY color space... it only defines the color matrix used in decoding YCbCr or YPbPr to RGB or vice versa (for example, high-def players convert RGB on the disc to YCbCr that is transmitted via HDMI to the display, the display then converts the YCbCr back to RGB for display). The matrix used for converting RGB to YCbCr and the matrix used to convert YCbCr both need to be identical for color to remain accurate. ITU Rec 709 defines both HD color space AND HD color encoding/decoding matrix. When you refer to SD color space, SMPTE-C is where that color space is defined.

The decoding matrix is different for SD and HD. So to get DVD or other SD programming to look right, you need to be using SD color space (SMPTE-C) and the SD color matrix (defined in ITU Rec 601). To get HD color "right" you need to be using the HD color decoding matrix and HD color space - both defined in ITU Rec 709. The decoding matrix controls how YCbCr (or YPbPr) is converted to RGB and how RGB is converted to YCbCr (or YPbPr). Use an inaccurate matrix and there will be errors in the conversion or decoding that can be difficult or impossible to "fix" with adjustments.

You can tell fairly easily if you have the right MATRIX selected by using something like the first Austin Powers DVD... with the correct MATRIX, the double decker buses and red in the UNDERGROUND signs will clearly be the right color of red. With the incorrect matrix selected, those shades of red will clearly be too orange.

Having the right color space selected is harder to see - it's better to measure the color spaces with instrumentation.

If your source and display both have RGB output options, you could, theoretically completely bypass the color matrix issue by setting both source and display to RGB mode (keeping in mind that PC RGB (0-255) and Video RGB (16-235)are not the same). But that's only how it SHOULD be... some display products convert RGB inputs to YCbCr first then back to RGB so with those you can't bypass the decoder/matrix even by using RGB mode all the time.

The problem you run into is that manufacturers may or may not use terms like "matrix" or "color space" accurately and it can be difficult to know exactly what they are talking about when the control is labeled Color Matrix, but the choices are NTSC, PAL, and HD. They could really mean the decoding matrix, but they might be referring to color space and just using the wrong terminology. That's where instrumentation is really needed to figure out exactly what the control is changing.

Yikes!

Will leave on HDTV for now until I get my colorimeter working.

db

high-def players convert RGB on the disc to YCbCr

Just a technical detail, but I think DVD and the HD formats store information as YCbCr 4:2:0 rather than RGB.

Have a JVC DLA-HX2 and am setting it up.
In the settings, it has a 'decoder' setting with options like NTSC and HDTV (also PAL). Which do I use? Hard to compare, but they appear to only change black level, but I could be missing something.

db, I looked at, what I believe is the manual for your projector

http://pro.jvc.com/prof/attributes/inst_man.jsp?model_id=MDL101519&feature_id=11

and there are two settings which you may be confusing.

"Color Profile" - with choices such as HDTV, NTSC, PAL, etc.

"Decoder" - with choices such as AUTO, NTSC, NTSC4.43, PAL, etc.

"Color Profile" looks to be the option to choose your color space. Leave it on HDTV (which hopefully means HD709) for now and when you get a colorimeter, you can measure the differences between the choices and see how close they come to any of the common standards.

"Decoder" is the matrix decoding that Doug is referring to. I would leave it on Auto which is the default.

hope this helps,


--tom