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Old July 30th, 2005, 11:24 PM   #1
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accuracy of Vegas' waveform monitor and legality of generated media

I was working on a project recently and noticed that on the generated media, the solid color white was reading, according to the waveform monitor, as being at 110%, instead of 100%. Is this right? Also, the solid black was reading at -10%, instead 0%. What's up with all that? Do you have to adjust each one just to make it NTSC legal?
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Old July 30th, 2005, 11:33 PM   #2
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Yeah those colors are "illegal".
Colors can be illegal if they are too bright/dark, too saturated, or too bright/dark and too saturated (you check this with the WFM in composite mode).

In this case, the generated media colors are too bright/dark. For NTSC, keep values between 16 and 235. So 235 235 235 is maximum white, and 16 16 16 maximum black.
For web work, use the full 0 to 255 color range.

Or you can just apply the broadcast safe filter (lenient 7.5 setup), and it'll clip things into legal range.

If you want to make something broadcast legal, there's more to this that what I wrote above. Making things broadcast legal limits your colorspace available and in that way lowers the quality of your video.
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Old July 30th, 2005, 11:55 PM   #3
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Thanks. I figured I could just bring the brightness up to 0 on the blacks and down to 100 on the whites using the "brightness and contrast" plugin. The vectorscope should tell me if everything's too saturated (i.e. illegal), no?
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Old July 31st, 2005, 07:59 AM   #4
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Josh,

The Vegas "Broadcast Colors" Video FX has several preconfigured levels:
"Lenient" - 0-100IRE
"Lenient-7.5 Setup" - 7.5-100 IRE
And several others, make sure and look at the settings.

BTW, I've used this FX several times and its sloooowwww to render. Works, but its slow.
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Old August 1st, 2005, 01:46 PM   #5
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I may have provided erroneous information in my last post:
Quote:
Colors can be illegal if they are too bright/dark, too saturated, or too bright/dark and too saturated (you check this with the WFM in composite mode).
It should be that colors can be illegal in two ways:
A- Luminance is not in 7.5IRE-100IRE range (systems other than North American NTSC may use 0-100IRE range).
B- The composite signal is below -20IRE (around negative twenty... you can go lower, but most broadcasters clamp at -20IRE I believe), or is greater than the ballpark of 110-120IRE (depends on where the broadcaster wants to clamp it at). Momentary peaks above 120IRE are ok.

See http://tig.colorist.org/archives/pub.../msg01675.html (read the whole thread)
I believe I misunderstood what was discussed in that thread... hence I thought there were 3 ways colors could be illegal.

In the digital domain there's no such thing as IRE. For proper monitoring, you should get an external hardware vectorscope to hook up to your equipment. However, if you set things up correctly (which is tricky because of the whole 7.5IRE confusion) then the scopes in Vegas can correlate to what you'd see on an external vectorscope. They will NOT correlate if you have things setup wrong (and that's easy in Vegas).

To setup things right in Vegas, go into the video scopes setting and check both boxes (if you're working towards NTSC but not for Japan).

Flip the waveform monitor into composite mode. Things should be between -20IRE and ~110-120IRE. Momentary peaks are ok.

Check luminance on the histogram. Everything should be between 16 and 235.

2- If you're going to DVD, I wouldn't worry about broadcast safe.

One thing you should aim for though is keeping luminance values between 7.5IRE and 100IRE. On the histogram, keep everything between 16 and 235. Everything else may clip (someone's DVD player may do it).

The waveform display will vary depending on whether you clicked the "7.5IRE" box (that setting does not affect the output from Vegas).
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Old August 1st, 2005, 09:44 PM   #6
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Quote:
Originally Posted by Glenn Chan
2- If you're going to DVD, I wouldn't worry about broadcast safe.
I hadn't heard that before. If I'm reading your post right, are you saying that DVD players today automatically clip video signals to make them broadcast safe? Or are you saying that DVD players can display colors outside the broadcast safe range with no problems?

Just wondering, because I've been limiting my video to broadcast safe maybe when I don't need to (I'm outputting to DVD). It would speed up my render times to take off that filter. I always thought that if you use illegal colors, especially whites that are too bright, you'd get distortion in the audio. Is that only true for broadcasts?
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Old August 2nd, 2005, 02:25 AM   #7
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One reason I was worried was because most times I've seen my stuff projected digitally, say at a film festival, the projection is significantly more contrasty than I KNOW the movie actually is. . .clipped whites abound when projected where I know none exist in reality.
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Old August 2nd, 2005, 10:27 AM   #8
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I hadn't heard that before. If I'm reading your post right, are you saying that DVD players today automatically clip video signals to make them broadcast safe? Or are you saying that DVD players can display colors outside the broadcast safe range with no problems?

Just wondering, because I've been limiting my video to broadcast safe maybe when I don't need to (I'm outputting to DVD). It would speed up my render times to take off that filter. I always thought that if you use illegal colors, especially whites that are too bright, you'd get distortion in the audio. Is that only true for broadcasts?
Some DVD players will clip the colors outside the "legal" range. Others won't. This is from reading websites about Joe Kane's calibration 'stuff'.

I don't think it's a big deal if you have illegal colors going through the DVD. Illegal colors could cause interference in the audio, but I think that's only if they have their TV hooked up via UFH/VHF. If they use RCA or better I don't think you'd get that interference. I should maybe double-check this myself.

You should still keep your colors in the broadcast safe range. Anything outside of 16 and 235 on Vegas' histogram likely won't be seen.
If you want to keep your colors legal, I'd put these numbers into the broadcast safe plug-in:
Luma min 7.5
max 100

Chroma 100 (you may be able to go higher, not sure; it'll likely be rare your colors are so saturated that you'd want to go higher)

Composite
min -33
max 133

check both those boxes.

That would correspond to 133IRE, which is the maximum for NTSC non-broadcast. You can't broadcast stuff with lots of 133IRE peaks in it because of FCC laws but DVD is non-broadcast so it should be ok.
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Old August 2nd, 2005, 11:42 AM   #9
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Know what's weird? I "graded" something using my Sony PVM 14m2u monitor, and when burned to DVD, the whites which looked a lot more "clippy" when I watched them on other TVs than they did on that monitor.

Do you think it's better to bring your levels (where they're illegal) within NTSC broadcast spec before you render, using various plugins (color curves, brightness/contrast etc) than to just let everything go and then simply apply the "broadcast colors" plugin after the fact?
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Old August 2nd, 2005, 01:52 PM   #10
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Know what's weird? I "graded" something using my Sony PVM 14m2u monitor, and when burned to DVD, the whites which looked a lot more "clippy" when I watched them on other TVs than they did on that monitor.
When was the last time you calibrated your monitor?
http://videouniversity.com/tvbars2.htm has a great tutorial on how to do it correctly.

My experience has been that most TVs are far from being set properly so I've come to trust that the signal is good leaving my place and the fault is with the end user. Not that you're ever going to convince them though :-(

The other issue, as Glenn said, is that different DVD players handle things in their own way. Some clip, some don't. Some add the 7.5 IRE of set-up and some don't.

Quote:
Do you think it's better to bring your levels (where they're illegal) within NTSC broadcast spec before you render, using various plugins (color curves, brightness/contrast etc) than to just let everything go and then simply apply the "broadcast colors" plugin after the fact?
I try to make sure my levels are correct before I apply any kind of filter. Others will probably disagree but to each his/her own.

Mike
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Old August 2nd, 2005, 05:09 PM   #11
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Thanks for the info, Glenn.
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Last edited by Brian Kennedy; August 3rd, 2005 at 12:05 AM.
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Old August 2nd, 2005, 05:17 PM   #12
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Heh. I actually calibrated last night, and I have those videouniversity instructions taped to the top of it (don't worry, I'm not covering any vents).

So, is the "safe" thing to do to check the 7.5 setup box on the waveform, and adjust things accordingly?
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Old August 2nd, 2005, 05:21 PM   #13
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Quote:
Originally Posted by Josh Bass
Heh. I actually calibrated last night, and I have those videouniversity instructions taped to the top of it (don't worry, I'm not covering any vents).

So, is the "safe" thing to do to check the 7.5 setup box on the waveform, and adjust things accordingly?
Glad to see you're doing things right :-)
As far as the "safe" thing, if your video is destined for (NTSC) broadcast, make sure you have 7.5 units of setup. Anything else and you don't need to worry about it.
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Old August 2nd, 2005, 07:49 PM   #14
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I guess I'd like something that'd be adaptable to any situation: film fest, broadcast, DVD, projection.
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Old August 2nd, 2005, 08:47 PM   #15
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Quote:
Know what's weird? I "graded" something using my Sony PVM 14m2u monitor, and when burned to DVD, the whites which looked a lot more "clippy" when I watched them on other TVs than they did on that monitor.

Do you think it's better to bring your levels (where they're illegal) within NTSC broadcast spec before you render, using various plugins (color curves, brightness/contrast etc) than to just let everything go and then simply apply the "broadcast colors" plugin after the fact?
I'm pretty sure broadcast monitors and televisions can display those illegal superwhites (things brighter than 235 on Vegas' histogram). It may be that in Vegas, there's some colors above 235. Some DVD players will clip those colors off, so that would explain the discrepancy.

For your second question:

You can work "in reverse". Apply broadcast colors to see which of your footage looks wrong/clipped. (The legacy filter can be helpful here because it can invert colors.) This is the faster approach.

Or you can work forwards, messing around with your footage so it's in the broadcast legal range and it looks good when everything is in the broadcast legal range. And then apply the broadcast colors plug-in to see what your footage will probably look like (since some DVD players will clip illegal values). Toggling the filter may help.
You can apply the filter onto the video preview level. Right click the green filter icon and choose bypass/enable all can toggle the filter.

Quote:
So, is the "safe" thing to do to check the 7.5 setup box on the waveform, and adjust things accordingly?
For North American NTSC:
Go into the video scopes options and check both boxes, the 7.5IRE and studio RGB box.
For the broadcast colors filter, base things off the presets for 7.5IRE.
That box doesn't actually affect the output from your camcorder to monitor. In your monitor, the menu may have an option for accepting 0 or 7.5IRE input. If you're using a consumer camcorder, probably set it to 0IRE and then calibrate (this may not make a big difference).

If you live in Japan or a PAL country, that information does NOT apply.

Quote:
I guess I'd like something that'd be adaptable to any situation: film fest, broadcast, DVD, projection.
Those are all different situations.

Film fest: No idea what format they use.

Projection: One difference from television: the best thing to do is to color correct with the projector that you'll be using, although that's a luxury you may not have. Colors can sometimes be washed out and blacks cut off/crushed depending on the lighting situation for the projector.
You may not need to worry about broadcast-safe, although you may if they feed the projector off a DVD player.

DVD: You can be much more lenient that broadcast safe and have more bright+saturated colors.

Broadcast: Illegal colors and improper formatting (timecode, tone in relation to program audio levels, slate, etc.) can get your master rejected, so you need to pay attention.

There's little things about each format which you can optimize for. In the case of broadcast, the little details become much more important because you can lose a client over it.
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