IRE Levels - Still confused!

[echo1434]

Ok, I've read a lot of posts on here and other places on the internet. I've even talked to tech support people. I've heard so many mixed things and now I'm more confused than ever. I've come up with my own theory here. Can someone tell me if I'm right?

I have two capture cards. An ATI All In Wonder 9600 and a Canopus MPEGPRO MVR. The ATI is a North American card, and the Canopus is based on the Japanese standard (0 IRE).

As I understand it, the ATI card assumes the source is 7.5 and reduces the IRE level to 0 when capturing. This seems logical because the captured video is definitely darker than the input.

On the other hand, the Canopus card assumes the source is 0.0 and thereby leaves the black levels untouched. I believe this because my captures look brighter when using this card.

Now here is additional confusion. I've heard that all DVD's (even NTSC) are mastered at 0 IRE. Is this true? This seems correct to me because from what I've heard, NTSC players will generally "bump up" the IRE level to 7.5 during playback.

So using my capture cards, a DVD authored using the file captured with the ATI will be outputted at 7.5, and the same video captured with the Canopus card will be outputted at 15 IRE (possibly causing the colors to be washed out).

Just going by looks, right now I'm using my ATI for videos that are 7.5 (so the DVD isn't too bright), and the Canopus for videos that are 0 (such as PAL), so they are not too dark.

This seems to be working out for me... But are my assumptions correct? Thanks in advance.

[anitract]

I don't have any input really, except that I am also interested in a response if anyone has any info on this that they would like to share. Especially concerning AIW cards, since that it what I currently use.

[echo1434]

There is no doubt that the default settings for AIW cards make the video darker. And when I try to offset it with brightness and contrast controls, it never looks right. So I'm thinking something else is at play here (IRE levels?).

Hopefully someone knows more than us!

[anitract]

I haven't actually noticed darker captures. They seem pretty spot on, but now that you mention it, I'm gonna look at some captures vs. source this weekend.

[andie41]

I am not familiar with the AIW cards - are you capturing directly to Mpeg or to AVI and then editing and converting to Mpeg? I would suggest to not assume the black level is correct, but open the captured video in a program with a waveform monitor, then adjust, if necessary.

[anitract]

Not sure about echo, but I cap to mpeg2.

[echo1434]

I capture to both MPEG-2 and AVI. The colors look the same — dark. The same goes for the Hauppauge PVR-350 I played around with one time.

[andie41]

My suggestion, regardless of the capture format is to check the actual black level. Most major NLE's come with a software WFM - I don't know what software you are using. Trevlac has provided an excellent free WFM plugin for Virtualdub ( clrtools ).

If your mpeg has 0 IRE black, your NTSC DVD player should add the 7.5, and all is well. If the mpeg (or avi) is not at 0 IRE, you should then adjust to 0 IRE. There have numerous detailed examples of how to perform this adjustment - levels filters, broadcast filters, etc. - depends on your editing software.

[andie41]

Followup to my previous post - if you are capturing directly to mpeg and find the black level is not correct, I would expect your capture card would provide a way to adjust before capture, in order to avoid re-encoding.

[anitract]

...so the AIW adjusting it to 0 (if that is really what it is doing) would actually be good, because when played back the dvd player puts it back to spec. Is that right?

[andie41]

so the AIW adjusting it to 0 (if that is really what it is doing) would actually be good, because when played back the dvd player puts it back to spec. Is that right?

Yes

[echo1434]

You know, I would just call ATI and ask them, but... The last time I called them, they (two people) told me that the card wasn't really meant to capture to various AVI formats. They kept recommending I capture first to MPEG-2 and then make it into DivX, "because that is an AVI format." Grrrrr...

For the record, ATI can handle any AVI format I throw at it, and the ATI staff seems about as knowledgeable as a block of wood.

[anitract]

lol well, I really know nothing about waveform monitors, otherwise I'd examine my clips.

[echo1434]

Ok, I was in the mood for a good laugh. I knew pretty much what to expect, but I gave good ol' ATI a call. These two quotes from the support guy sum it up pretty well:

"I'm not an expert on video."

"I've never heard of IRE black levels."


I got him to escalate my call to the technicians, but the wait time was ridiculous and I had to get off the phone. I'll try back at a later time, but he told me he had already talked to them about, so he couldn't assure I'd get an answer.

Need I say anymore? hahaha

[vhelp]

Evening everyone.

Guys.. the answer is simple.

If you are capturing with other capture apps.. ie, vdub or avi_io
or virtualVCR, etc. just go to the following and adjust the IRE
accordingly, to 0.0 or 7.5 IRE:

usually under Video Settings.. ie, avi_io is

** Video Settings
** Source
** [NTSC-M] = 7.5 IRE = darker -- (on some caps dev, is the default)
** [NTSC-J] = 0.0 IRE = lighter - (sometimes its, NTSC-Japan)

The rule is simple to follow here.. if sources are from your
** cable; satalite; vcr; laserdisc; dvcam; camcorder;
-- Fig A. --

these are all outputing approx 0.0 IRE levels, thus setting to an
NTSC-J = 0.0 = lighter is optimum because the source is equal on
both ends.

The above setting will not make it lighter, (though it will look
ligher) ..it will "match" the source, which is what you want to
do in the first place. You do not want to "amplify" your sources
captured video IRE levels.

Note: you can however, get away with "amplifying" to a 7.5 IRE
by changing the IRE from NTSC-J, to an NTSC-M (if it is not already
there) This will somtimes work for the better. But not in every case
because the source being captured is not always standardised as far
as IRE levels go. That is, the "black" count. These source mediums
that I mentioned under Fig A. are lighter looking to begin with,
during the outputing to your capture card.

Now, the other rule is like this.. if your source is from your
** DVD Player

DVD players usually output approx 7.5 IRE levels, (indicated as rich
blacker looking video) thus setting to an NTSC-J = 0.0 = lighter is
optimum because the source is already "amplified" on the DVD player
and is being outputed to your capture card as NTSC-M this way.. thus,
setting your IRE down a notch (on your capture card software) to NTSC-J
is the best setting to use, else you would be "amplifying" the black
levels even darker otherwise.

One thing I'd like to note here however, is this. In my many testings
of video player units, such as.. ie, vcr's; etc. I have found that
some do not ahur to the standardised setups. Thus, the IRE is a
perfect example. Some VCR brand/makers etc will use a lighter IRE
setup vs. others.. and darker, vs. others. These are "screws" that
taint the understanding of what IRE setup is all about and how to
properly set them in a given Capturing Project.

My best guess theory is like this ...

When the source is a DVD player, the decision to "amplify" the IRE
levels on the output.. ie, RCA / S-Video leads.. was to maintain
the level of Theatrical Viewing Experience vs. the tipical dullness
look from Cable/Satellite broadcasts.

A quick "self-test" can be done to illustrate. Watch your TV broadcast
shows, and VCR, and Laserdisc source mediums. Notice how they ALL
look alike in brightness (or IRE) levels. This is why I rounded them
up inside Fig A. above.

Next, compare the above viewingh "self-test" against a DVD player's.
You'll notice right away that the brighnesst (or black) levels are
more richer than the above Fig A. listing of source mediums.

That's about it for IRE levels and their setups.

To recap:
** If source is from: cable; satalite; vcr; laserdisc; dvcam; camcorder;
use NTSC-J as your IRE setting. (you can get away w/ NTSC-M in some cases)

** If your source is from: DVD Players, use NTSC-J.

-vhelp 3569

[anitract]

wow...i am trying to digest that great info vhelp, but my brain...it totally refuses...lol *waits for more input*