Go-to Guide for Source Options - Page 6

I literally studied this thread a while back. And learned a great deal from it thanks mostly to Chris's help. I don't remember this issue being discussed. IRE vs % yes, but not the fact that Avia Pro and DVE pro have levels that are different based on IRE and % respectively.

A fly in the ointment when I when to use DVE Pro with software expecting IRE levels:

Probably not appropriate for this thread, but certaintly related I think. So here's the link to a new thread to see aht I'm talking about:

http://www.avsforum.com/avs-vb/showt...&&#post7044635

grrrr. Another lack of standards.

Here is a simple question. If I have an lcd projector and an iScan Ultra, is a dvd players inability to pass blacker than black a deal breaker? How much of an issue is it in practical terms?

EDIT - ok, for the sake of not carrying on in this thread, thanx for the feedback. I still don't understand exactly how the blacker than black signal works in practice.

Is the btb signal really mostly only "useful" when you set your calibration and then after that it has no effect? Or is the btb signal actually involved in preventing the clipping etc during actual playback? Is it easy to tell if a player has btb and what do you notice if the player does put out have btb?

It sounds like a good thing which can really help in calibrating, but something which is not the end of the world picture wise. I suppose I will try to check the dvd players I have right now to see which units pass btb. I will be pissed if the ones I have now pass btb if the one I am getting does not....but then again, the one I am getting is really only for region free and dvd/audio sacd and other format use.

Any more simple bottom line info about the implications of btb would be greatly appreciated.

thanx chriswiggles [ PS enjoying your Marantz receiver? I still enjoy the ole SR 8000 ]

Yourself included

The IRE scale is not absolute, it's relative...and also it's a measure of the
gray scale or luminance. "IRE are NOT simply a representation of volts"!

Sorry Thomas but you are wrong - do we have to get into quoting Poynton? IRE is referenced back to Video signal voltage range.

White sits at ~714 mV, Black (for NTSC systems) sits at ~53 mV. If that isn't a direct relationship I don't no what is.


http://zone.ni.com/devzone/nidzgloss...2568A100781B2A

ted

From Snell & Wilcox glossary:
Acronym for the North American 'Institute of Radio Engineers'. Also refers to the measurement units introduced by this organization. As defined by ANSI/IEEE standard 205, 'IRE units are a linear scale for measuring the relative amplitudes of the component.

From Tektronix Standards overview:
Eventually the IRE (later to be the IEEE) established a unit of measure for video signals. This "IRE unit'' was defined as 1% of the video range from blanking to peak white, without reference to the actual signal voltage. Although defined as a ratio,

Oh yea, one other term that I have been accused of misusing
From Tektronix glossary of useful terms:
"GAMUT-
The range of voltages allowed for a video signal, or a component of a video signal. Signal voltages outside of the range (that is, exceeding the gamut) may lead to clipping, crosstalk, or other distortions."


Dave

Thomas,

I've no problem with the use of the term "relative" after all an IRE is a "unit". However within the context of this thread what do you think that unit should be?

Offer another unit outside of its applicability to NTSC that might be useful here.

Since as you claim "it's a measure of the gray scale or luminance" then state the unit measurement of that graphing, and while you are at it tell me how many Ft Lamberts, Ft Candles, Lux or Lumens are represented by 100 IRE?

As a master of tangential thinking you should be able to find something, and when you do please explain it within the context of this thread.

btw did you notice the '~'? that means "nominally" in that context.
ted

Sorry Chris, this entire section is WRONG! I already corrected you, yet you continue to discuss things you don't comprehend!
"IRE is a relative linear scale. It doesn't refer to any particular voltage or digital level until you specify the signal standard being used."

thomas

http://www.poynton.com/PDFs/Merging_RGB_and_422.pdf

Test signals characterize the electrical performance of a video system. Standard video test signals include elements that are synthesized elec-tronically as sine waves, and injected onto the signal. Many of these elements have no legitimate R'G'B' representation. Since these signals can be conveyed through Y'C B C R without incident, some people claim
Y'C B C R to have an advantage. However, in my opinion, it is more important to allocate bits to picture information than to signals that cannot possibly represent picture information.

This is a great resource.

in the above paragraph (found from part 2 of Chris' awesome write-up), there appears to the a typo. It appears that the intent is to maintain Studio levels, so am I correct in assuming that you should always select "Normal" or "Video" on your DVD player? If so, don't you mean to say "the former is clearer" rather than as printed "the latter is clearer" (4th sentence in paragraph)?

I think he is referring to the phrase ""Video/PC" as opposed to the phrase"Normal/Enhanced(or expanded)"..

IOW he was referring to the description, not the result, as being clearer.

Hopefully, the author will reply and clear things up.

No reason for a bump, thread is a sticky.

larry

Nice guide!

Im 32 years old. How did I survive all this long without reading this?

I would love to say "I DONT CARE", but I do care and this thread was a great help!

This thread was referred to on a current thread as a source of information that would answer another posters question. So I have read it and find it does not appear to agree with what I have read elsewhere, so thought I would ask why?

From the original post:

"I will refrain from calling them ‘whiter than white’ because this implies that they shouldn’t normally be present or visible in the final picture. They should be, unlike BTB"

"In a system that outputs black at 0 IRE, BTB data will be output at voltages slightly below 0mV (simply negative volts). If you’ve digested that correctly, you realize that BTB data can be maintained in BOTH situations"

Below is my limited understanding, is it correct?

In the Pal analogue signal there is a blanking interval to give the display time to move to the next line or the next frame of the image. In this blanking time there are sync signals. Also during this blanking time the analogue signal is clamped to 0volts by using a capacitor. Because if it is not clamped the signal will wander and the black level in the image will not remain constant (since white is created by higher voltage, a bright image could drag the bottom of the signal up from 0v). If this clamping extends into the part of the signal that syncs black it is called a black level clamp, PAL black is 0volts so it is being clamped to 0volts.

I do not understand how if the above is correct, why blacker than black should or could be passed through the system. My understanding is it was neccessary in analogue systems because they might not have very good clamping of the signal or it might wander up as it displayed a image line with a high average brightness, so some tolerance to black level wandering was needed. Whiter than white information is also I think present in analogue systems because signal level could wander up, at the begining of the line whiter than white would equal white, but at the end of the line white could equal white, if whiter than white was not present in the signal white would be grey at the begining of the line. So my understanding was blacker than black and whiter than white are holdovers from the analogue age when image brightness might not hold steady across the image, you might need to drag an analogue wave signal down to black or up to white when the voltage of that signal could be wandering about.

In a perfect CRT I think the idea is that it is not needed as the signal level does not wander, unfortunately people did not have perfect CRTs so it was present in the analogue signal, but on a perfect CRT the information would not be displayed, in effect it would be clipping below black information and whiter than white information would be white anyway. Calibrating to incorporate blacker than black and whiter than white apears to me as calibrating to be equivelent to the worst crt display it was designed to cope with. I thought they only existed in digital as a legacy to analogue and served no usefull purpose with digital displays.

If blacker than black is desirable up to the digital non-crt display, and according to some displaying some blacker than black information is desirable. What visible negative impact does it have if the source is clipping it and are sources that clip it failing to meet the consumer spec and of a faulty design for doing this.

If whiter than white if it is desirable to actually display. What negative impact on image quality is there from clipping it and again are sources that clip it failing to meet the consumer spec and of a faulty design.

If I do not display blacker than black or whiter than white I gain contrast, which improves perceived image quality. What do I gain if I display them.

I am confused...
My player Pioneer DV-600 has an option to show BTB and WTW.
How should I configure it? The readme of the firmware that allows this option says: Enable BTB, put the players Brightness to +1 and Contrast to -1. So it gives BTB and WTW info.
If I do this I can see BTB and WTW bars from GetGray DVD. Should I calibrate my tv to see or not to see BTB?
Thank you!

Let's see how much I remember from all this stuff when it was the hot topic. For analog video, you usually have the choice to have "black" be 0 or 7.5 IRE. IRE voltages are not absolute, they're sorta like "voltage differences". I'm not sure if the PAL standard is for 0 IRE to be black or not, but then again that is not necessarily 0 volts (or mV). 0 IRE can be +2mV as long as both sides "agree". So when the player outputs a "level" for black, the display recognizes it as black and displays it. That's my best shot remembering off the top of my head. You may want to PM Chris Wiggles and point him at your post. He should be happy to explain.

larry

Sounds like a load of BS to me. In digital video, "black" has value 16 (for luma in component video). So, on a DVD where there is "black" the digital value 16 appears. If the DVD player works correctly, the value 16 will be output on the HDMI cable to the display. If you increase brightness +1 in the player, it will take the value 16 and add 1 (or 2, or 3, or more depending on how the brightness control is "tuned"). So, now the 16 (black) is no longer output as 16, but as 17, or 18 or some other number higher. Your (properly calibrated) display sees it and it does not output black, but something lighter.

Ok, so now if you have BTB on a disc, eg. 15 or 14 or lower, the "player brightness at +1" will cause the value on the disc to be output at 16 or 17 or something. BTB is not being output, but some brighter shade of black/gray. Changing brightness (or contrast, or any other color/tint) on the player modifies the digital video values coming from the disc. That's not why you buy a DVD player, you buy it to output what is on the disc.

The way to tell is BTB is being output by the player is to properly calibrate your display so that "black" (16) is "black" (no light) on your display. Once you do that, anything at 16 or below will show as "black". If you want to see if BTB is passed by the player, view a test pattern with BTB information. Then raise the brightness on the *display* and the BTB information should be seen after raising brightness a tick or two or three. If you don't see the BTB bar or whatever, the the player is probably not sending BTB data. Raising the brightness on the display takes the BTB (eg 15) and adds adds 2 or more to it so that it is 17 or 18 allows them to be seen. In fact, you should be able to lower brightness on the *player* and still be able to see BTB video on the display by raising brightness. It's all just math. Subract some on the player end and if you add enough on the display end it will be visible. Most players don't modify the video when controls are in the "neutral" position, but lowering the brightness on the player will guarantee it is passing BTB video if you can see it on the display after raising brightness. If the player is not configured properly at the factory, it could possibly add (or subract) something to the video data value. That's why we have the nifty calibration discs.

BTB video should not be seen on a digital display when properly calibrated. "black" should be set to "panel off/no light" so it's kinda hard to display something darker. BTB is necessary for scaling and to help maintain proper black levels for CRT displays if the BTB data is on the disc.

Most digital displays can output WTW when calibrated correctly. And if the player can output BTB then it is most likely outputting WTW too. If no BTB is output, then WTW is probably clipped also.

larry

Thank you PooperScooper!
I did the changes I wrote (players brightness +1, contrast -1) (that is the only way to pass BTB and WTW) and reduced my tvs brightness and increased my tvs contrast. I calibrated so, I can't see BTB, but now I can see WTW and the picture seems a lot better than before.

I have a Pioneer Elite DV-58AV with three HDMI Color settings:

Full Range RGB = 0 Black to 255 White
RGB = 16 Black to 235 White
Component = ? Black to ? White

I wish to know the missing values for the Component mode. If the Black to White range is the same as the RGB mode, then what's the difference between the Component and the RGB modes? Thank you.

Isn't component going to be YPbPr (http://en.wikipedia.org/wiki/YPbPr) instead of RGB? I'm not sure if the luma channel has an extended vs studio range corresponding to RGB.

-Bill

I believe YPbPr is analog, and YCbCr is digital, but they are both Component Video levels. I am curious about the digital numbers from Black to White.