IRE settings

[gshelley61]

Wow, awesome stuff. 8)

[Frobozz]

Here's another good article on the IRE black levels:
http://www.signvideo.com/dv-black-levels-dvd-authoring-mpeg-2-part-1.htm

[lordsmurf]

It's almost gotten to the point where I don't care about definitions anymore. So, let's try for some real-world examples:

This is image I see on tv. Any tv, the tv is correct:


I record on the JVC, and rip to my HDD.
When editing the file, I see this...

Observation: It's darker, the whites aren't quite totally white, black is black. Some of this could be my monitor. In fact, what you see may be ENTIRELY different, if your monitor is borked.

I author a DVD, and play this on the same tv, with IRE 7.5 player:

Observation: Identical to the source.

If I use one of those cheapo Chinese player, with IRE 0, or if I set my expensive NTSC player to IRE 0, I see this:

Observation: Too dark, contrast is whacked out. Black is too black.


That, my friends, is what happens.
What's even more confounding, is that the commercials, and the show following The Simpsons, was the same ... but different.

Now see... Smallville ... it's definitely been encoded to IRE 0, where the input was easily IRE 7.5 from the broadcast antenna. Check this... it's much darker than the broadcast was, on the encode shown here:

Observation: Play is on the NTSC 7.5 IRE player .. poof! ... perfect (or as good as the original broadcast, which I think was a little light anyway). Darker colors/contrast/blacks in the editor, funky contrast on the IRE 0 chinese player.

None of my tv stations really match up, neither do cable, nor did satellite when I had it. In fact, when I was using my ATI AIW for satellite captures, I maintained a list for "gamma settings" for each channel I used, because they all varied by a small amount.


And there you go .... chew on that one for a while...

Standards are out the window. This is why we have contrast/brightness adjustments on everything, and we more modern DVD players and tv sets have "modes" to control black level, etc. Just be sure your recorder doesn't butcher anything too bad, either by obliterating lights or darks by extreme amounts.

[edDV]

Put samples on a DV-AVI and i'll post the waveforms.

PS: can't do it from screen caps.

[lordsmurf]

Put samples on a DV-AVI and i'll post the waveforms.
PS: can't do it from screen caps.

I don't have DV-AVI, and a couple of those images are simulated in Photoshop because I'm not going to tear my house apart for a couple tests (mainly the good NTSC 7.5 IRE player), so they're not appropriate for advanced scanning anyway.

While that may be nice, I'm simply not going to put forth that much time and effort into it.

[hrlslcbr]

...Setup should exist only on the analog NTSC (composite and S-Video) outputs (not on component out)...

So you say that my DVD player (connected with component cables) should be set to 0 IRE and NOT 7.5 IRE?

[edDV]

...Setup should exist only on the analog NTSC (composite and S-Video) outputs (not on component out)...

So you say that my DVD player (connected with component cables) should be set to 0 IRE and NOT 7.5 IRE?

My assumption was they would behave like broadcast equipment, but they don't.

Pioneer in my example, puts setup on composite, S-video and component analog Y.
The Chinese players were 0 IRE black on all outputs. Like Japanese NTSC.

That is my data so far.

Broadcast equipment like Betacam VTRs have dip switches for everything.

Maybe the DVD player and recorder databases here should include setup (zero or 7.5 IRE black) default and switch info.

[hrlslcbr]

I am asking because my DVD player has an option of 'black level', which makes it output 0 or 7.5 IRE, that's all.

[BJ_M]

set it to what looks good on your TV (depends what you have) -- as stated the 'standard" is shot to hell , which is what ive been preaching about dvd players for many years here ..

on the popular uvw1800 beta sp there is no dip switch for IRE , but its in the menu and setup under the right front flap .. other units such as the 500 d-beta there are also setup controls in the menu...

[hrlslcbr]

Ok

[edDV]

I am asking because my DVD player has an option of 'black level', which makes it output 0 or 7.5 IRE, that's all.

You should match the other inputs to your TV so that minimal adjustment is needed when switching from TV to Cable box to VCR to DVD player.

In North Amaerica, this would normally mean 7.5 IRE for black.

It gets more complicated with computers, game boxes, camcorders and other types of input.

[BJ_M]

he didnt say what kind of TV he has - is why i wasnt more specific , my samsung HDTV dlp and my NEC Plasma want 0IRE , my other HDTV CRT likes 7.5 but it has a wacky autobrightness/contrast and im comp'ng ..

my video projector = doesnt mater , goes through a processor first and gets rescaled for the chip including levels (0)

[lordsmurf]

It gets more complicated with computers, game boxes, camcorders and other types of input.

Yeah. XBOX is too light on games.

[edDV]

I'm going to inventory black levels on the various boxes around here.

[gshelley61]

I also have a Samsung DLP HDTV, and it definitely is a 0 IRE black level display. Nearly all the newer TV's and displays can handle 0 IRE, and will benefit by producing "blacker" blacks. If I'm not mistaken, the only reason the NTSC black level was set to a dark grey 7.5 IRE rather than true video black 0 IRE was because in the early days of television, NTSC broadcast signals were unstable with the black level set to 0 IRE, and TV's had a hard time with those signals as a result. Of course, time and technology have resolved those challenges and NTSC with 0 IRE black level works just fine... a modern TV set is not going to freak out if it receives a true video black (or below black) signal. Is that about right, edDV?

[Marvingj]

Great Information; THIS DEFINITELY NEEDS TO BE A STICKY!!!!!!!!!!()
Idea

[sync]

None of my tv stations really match up, neither do cable, nor did satellite when I had it. In fact, when I was using my ATI AIW for satellite captures, I maintained a list for "gamma settings" for each channel I used, because they all varied by a small amount.

And there you go .... chew on that one for a while...

I chewed on it a bit and I'm getting indigestion.

How do you handle all these variances when capturing TV with a DVD recorder?

[zorankarapancev]

While you don’t have any technical control over all those different productions that you watch on your TV, you should know that the TV studios and your TV set are design to work and support the official standard in this part of the world – NTSC system - 7,5 IRE black level. That is your safest start point before you will decide to change anything on your recorder or TV screen in order to compensate for all those variations in TV programs. I guess, if you are really picky about picture quality, you will have to change your settings quite often.

[edDV]

I also have a Samsung DLP HDTV, and it definitely is a 0 IRE black level display. Nearly all the newer TV's and displays can handle 0 IRE, and will benefit by producing "blacker" blacks. If I'm not mistaken, the only reason the NTSC black level was set to a dark grey 7.5 IRE rather than true video black 0 IRE was because in the early days of television, NTSC broadcast signals were unstable with the black level set to 0 IRE, and TV's had a hard time with those signals as a result. Of course, time and technology have resolved those challenges and NTSC with 0 IRE black level works just fine... a modern TV set is not going to freak out if it receives a true video black (or below black) signal. Is that about right, edDV?

In the early days, TV sets and some broadcast equipment couldn't reliably "blank" the CRT beam retrace without this extra 7 1/2 % safety margin from the zero IRE horizontal and vertical blanking level. Also any signal excursions below 0 IRE damaged transmitters (visualize sparks and fire). Even though gating technology was later invented to blank the retrace beam, there were so many TV sets out there that it was decided to maintain 7.5 IRE black to avoid obsoleting the existing TV sets.

Ten years later, in the late 1950s and through the 1960's Europe (except France) obsoleted their early TV systems in favor of an all new 625/50 common standard that would support the new PAL color standard. Japan went color about the same time and opted for zero IRE black when NTSC color was introduced there. This is the model for how the FCC is currently introducing DTV here. There is a temporary period where both systems exist in parallel.

Brit history for example - See 405 line standard
http://images.google.com/imgres?imgurl=http://www.pembers.freeserve.co.uk/Test-Cards/1...ial_s%26sa%3DG

The conversion to DTV is an opportunity to change black to 0 IRE, but one must deal with the legacy 7.5 IRE souces remaining in that environment (e.g. VCR) and the reception of non-DTV channels. Not to mention setup existing on cable and satellite boxes.

DTV/HDTV sets need to be programmable on an input by input basis to make this conversion work.

The Euros used to make fun of the USA NTSC system as "Never Twice Same Color", that was fixed but the combination of NTSC, DV and DTV now means NTSL "Never Twice Same Level"

[hrlslcbr]

he didnt say what kind of TV he has...

Just a normal 21" interlaced panasonic TV. Do you know HOW to check what IRE setting is right for different devices (capture card, TV, etc)?
Thank you.

[edDV]

he didnt say what kind of TV he has...

Just a normal 21" interlaced panasonic TV. Do you know HOW to check what IRE setting is right for different devices (capture card, TV, etc)?
Thank you.

I'm beginning to inventory my signals for black and white levels. Last night I looked at all the channels on the cable box when routed to my Vegas waveform monitor. My local Comcast system is in the process of being rebuilt so it is far from tuned up. All channels had setup but not all were at 7.5 IRE. Some like TBS were down at 2 IRE black. This would put TBS at -5 IRE in DV and the Mainconcept encoder would saw off the lower 5 IRE. Many channels had white excursions above 100 IRE some were even clipping at 109 IRE.

As our TV sets get better, we will become more sensitive to these level differences in the living room over time. When capturing these sources to 8bit video we need to start paying more attention to setting proper black and white levels before they hit the A/D.

My intermediate viewing solution is to create two settlings profiles on my HDTV monitor. One is for 7.5-100 IRE that will be used for cable, DVD Player, VCR and laserdisc playback. The other profile 0-100 IRE will be used with my DV calibrated editing environment. The DVD player and Canopus ADVC-100 will be used to "bridge" between the two environments.

Reference for the 7.5-100 IRE settings will be the Digital Video Essentials (DVE) DVD http://www.audioholics.com/techtips/setup/avhardware/DigitalVideoEssentialsDVDreview.php

Reference for the DV environment will be the Vegas Editor test signals.

[gshelley61]

edDV, you are the professor! The info is great. One question though... in the case of DVD playback, isn't it better to take advantage of the 0-100 IRE encoding native to the format rather than to add +7.5 IRE setup (assuming your TV is OK with that)? Most NTSC DVD players have the ability to output at 0 IRE black level... you just have to set them that way.

[edDV]

A DVD player with that adjustment can be made to work in either "IRE space" 7.5-100 or 0-100 IRE. 0-100 IRE has more dynamic range that may actually be visible.

The problem I am observing on the scopes is that shortcuts are being made when 7.5 IRE setup is being applied. Some equipment and software is just moving the entire IRE space up 7.5 IRE (i.e. 7.5 black and 107.5 white) when it is supposed to be mapping to 7.5-100 IRE maintaining the 100-109 space for overshoot safety.

The Canopus ADVC seems to be doing this correctly when you look at those Laserdisc results. The whites stay put while the black is adjusted.

[BJ_M]

Some equipment and software is just moving the entire IRE space up 7.5 IRE (i.e. 7.5 black and 107.5 white) when it is supposed to be mapping to 7.5-100 IRE maintaining the 100-109 space for overshoot safety.

yes - similar to coring

[gshelley61]

A DVD player with that adjustment can be made to work in either "IRE space" 7.5-100 or 0-100 IRE. 0-100 IRE has more dynamic range that may actually be visible.

The problem I am observing on the scopes is that shortcuts are being made when 7.5 IRE setup is being applied. Some equipment and software is just moving the entire IRE space up 7.5 IRE (i.e. 7.5 black and 107.5 white) when it is supposed to be mapping to 7.5-100 IRE maintaining the 100-109 space for overshoot safety.

The Canopus ADVC seems to be doing this correctly when you look at those Laserdisc results. The whites stay put while the black is adjusted.

The DVD players I recently measured (with the meter on my SignVideo Proc Amp) for output levels when set to both 7.5 IRE and 0 IRE black level behaved differently from each other. Using the THX multi-purpose test pattern, which I assume is 0-100 IRE, the s-video output levels of the Panasonic A320, the Panasonic E55, and the Pioneer DVR-220 (set to 7.5 IRE output black level) all read 7.5 IRE black level and 100 IRE white level. When I set the units to 0 IRE output black level, something interesting happened. The Panasonic A320 and the JVC DR-M10 (which apparently is fixed at 0 IRE output) both read 0 IRE for black level and 80 IRE for white level, while the Panasonic E55 and the Pioneer DVR-220 read 0 IRE black level and 100 IRE white level. So, I guess that means the A320 and the DR-M10 produce slightly reduced white level for some reason? Or, perhaps the test pattern is at 75% luma and the 7.5 IRE setup is simply shifting the whole IRE space as you mentioned?

[lordsmurf]

None of my tv stations really match up, neither do cable, nor did satellite when I had it. In fact, when I was using my ATI AIW for satellite captures, I maintained a list for "gamma settings" for each channel I used, because they all varied by a small amount.

And there you go .... chew on that one for a while...

I chewed on it a bit and I'm getting indigestion.

How do you handle all these variances when capturing TV with a DVD recorder?

You don't. Just try to deal with it as best you can, taking advantage of brightness/contrast/black controls on the tv and dvd player. Hope your source is not too far whacked out, and be sure you use equipment that does not obliterate the black/contrast/white too much. As far as I'm concerned, Panasonic is the worst recorder in this regard, with early models destroying lights/whites, and later models destroying darks/blacks. Pioneer, JVC, some LiteOn, and a couple others represent the mid-range of recorders you want to achieve the most desirable signals.

I've long found myself tweaking one thing or another on the tv to get a certain tv/satellite/cable station, VHS, DVD, etc ... to look correct. It takes about 5 seconds with the remote, and I'm done.

Great Information; THIS DEFINITELY NEEDS TO BE A STICKY!!!!!!!!!!()
Idea

It's been cleaned up a bit (for readability) and sticky-fied.

[Yvon]

edDV, you are the professor! The info is great. One question though... in the case of DVD playback, isn't it better to take advantage of the 0-100 IRE encoding native to the format rather than to add +7.5 IRE setup (assuming your TV is OK with that)? Most NTSC DVD players have the ability to output at 0 IRE black level... you just have to set them that way.

With my Sharp recorder, I have to raise the IRE to 7.5 for all DVDs on playback except the ones that were burned by it. Commercial DVDs are too dark otherwise. So, I suppose that my own recordings are burned at 7.5 IRE.

Yvon

[vhelp]

Evening all

@ gshelley (and others)

I would also like to note here, that I'm working on a tool that
might help us with some of these tests. When I complete work on one of
the tools, I may remember to inform you all about it. Until then.. keep
pluging away.

Found here:
--> Pioneer DVR-220 video recording test

I made mention in the above thread, that I was in the middle
of developing a tool to help us in some areas of these testings.
I realize that you and others here are limited in providing certain
types of pics that would serve beneficial to our perception, and
this tool might come in handy for those trying to demonstrate
there research results. (But it could be used for other purposes)

And, the reason I'm posting this news here, is because it more closely
relates to the subject, IRE settings and the tests that come out
from it. Anyways. The tool is almost ready.

My only two problems now, are:
* Coming up with a good name for it and,
* Where to post this tool (and discuss)

-vhelp 3169

[BJ_M]

all you need to do is encode a PLUGE chart -- like the on i posted in the advanced conversion section

[hrlslcbr]

OK, there's something I don't understand. In the first post, the 'chart' shows IRE 0 as 0 for digital, but I think it should be 16. AFAIK, DVD's are encoded with possible luma values of 16-235, that's why encoders like CCE have an option to 'compress' the luma to 16-235 and not 0-235. Is this correct?