Well.. NO

It is best to correct the problem shots and to create your graphic elements within the correct range. The filter does its best to do a nice job with your footage, but you don't have the control over how it is done. The outcome might not be quite what you were looking for. It is meant as a down and dirty fix.

It would be like mixing the audio by putting limiters on all channels. A channel that is too hot would be squashed when you could get a better sound by just bringing down the volume.

I adjust each scene and then throw Lenient on the track at the end which forces 100-0. Doing this I watch that footage over and over with and without the BC and I almost never see a difference with footage except on the scope. Where it looks different I go to that scene and adjust it again.

There's different ways of approaching this.

A quick and dirty way would be this:
Set preview mode to draft.
Apply the legacy broadcast colors filter. Click on the invert button.
Play through your project
Any illegal colors will be inverted and plainly visible.

If there are shots with large areas that are inverted, you'll know they'll need manual tweaking.

Go back and delete the legacy BC filter. Add the broadcast colors filter. Use the conservative 7.5IRE setup preset. On default settings, it will clip illegal colors.

The better quality method of color correcting:
Go through your footage and work on the problem areas. The method above (with the inverting colors) will pinpoint the problem areas.

Toggle the broadcast safe filter as necessary to see clipped information.

Luma out of range:
use the Color corrector filter. Play with gain and offset to move lumiance values in range. It's easiest to look at the histogram- aim for between 16 and 235.

You can also use color curves, but that's a little trickier and harder to describe. It can give better quality with rolling off of highlights and shadows. The broadcast colors filter does something similar.

Composite (luma and chroma combined) out of range:
By default, the broadcast colors filter will only lower saturation until the color is legal. It looks better if you lower a combination of luma and chroma. What you do here is an artistic judgement.

Chroma out of range:
Generally don't have to worry about this, but you can use saturation adjust if you do have problems. The smoothness function of the broadcast colors filter should do something similar I think.


Quick and dirty way of doing things:
Make a custom curve that's s-shaped to do the film gamma thing. Deselect the curve
Move the bottom dot thing so that 0 gets mapped to 16. Move the top dot thing so that 255 gets mapped to 235.
It may help to do this on the gradient generator (not the ramp test pattern). The legacy BC filter can also help.
Use the arrow keys on your keyboard too.
Save that as a preset.

The other thing to do is to make a "Color Corrector (Secondary)" Preset to lower brightness on colors with illegal composite values.
Try:

Gain=0.925

Limit saturation:
Low 52.9
High 162
Smooth 97.8

Limit Luminance
low 201.9
high 255
smooth 108.5

Apply both filters before broadcast colors.

You'll get pretty good results without having to do manual tweaking.

For DVD, that information will limit the color space available to you. In the broadcast colors filter, put in 133 under composite max (instead of 110). For broadcast you can up the number to 115~120 to take advantage of higher color space (if the broadcaster will allow that; read their specs). 110 is to be on the safe side.

I'ev been doing some Loop CC. I've noticed, as one would, the Scopes dancing and prancing up an down. What would be neat if we could get something akin to "clipping" notifacation in Sound Forge. Then maybe we could get some function that would allow us to apply redux over that range. Keith it was your, "It would be like mixing the audio by putting limiters on all channels. " which made me start to think like this - cheers!

glennchan ! Brilliant tutorial - THANK YOU! You lifted some of the veils over areas of my "fuzzy" understand ( seeesshh, what a bunch mixed metaphors there then? ).

Ok, Guys, when it comes to delivery and the different variables for this, is there a table available on the NET that allows us to see these DVD or Broadcast or Projector or TV or LCD or Cornflakes Box method of delivery?

Great thread . . this is being kept, till I drum it home in my bone brain!

TIA

Grazie

Grazie, I haven't seen such a list.

From what I know:
Broadcast: 110IRE to be conservative. If you read the station specs, you should be able to up things to 115-120IRE so you give yourself more color space to play with.

DVD: 133IRE (composite). I think. If you go too high, you might cause buzzing in the audio.

VHS: No idea, although I suspect it'll have problems with bright+saturated colors. The tape format itself has limitations- sometimes you see colors on VHS smear all over. I haven't played around with VHS much.

betaSP: ???

projector: You could probably do 0-255 ("studio RGB" in Vegas) instead of 16-235. I don't think you need to worry about broadcast safe colors, although I haven't tried. It'll probably depend on the project. If you have the time, hook up the projector to your Vegas system and run test patterns through it.

Grazie: The legacy broadcast colors filter and its invert function is kind of like a clipping notification.

glennchan - thanks! The pennies are starting to drop, G

This is a very useful thread as I'm preparing a project for both PAL and NTSC DVD but NOT broadcast.

I want to preserve the maximum dynamic range so I really want to add the minimum clipping necessary, but of course I don't want it to cause buzzing or other problems on customers' TVs. I definitely plan to experiment with Glenn's ideas for getting the footage right in advance of the broadcast colors clamp but with an imminent deadline I just need to set up a preset in the BC plug-in to keep me safe.

My project is PAL DV and looking at the histograms and the inverted mode of the legacy broadcast colors plug-in, there's plenty of footage below 16 and up near 255.

For NTSC DVD, if I add the "lenient" preset of the broadcast colors filter and then increase the composite max to 133, will I be safe? Is even this more limiting I need to do? Should I check 7.5IRE too or can I forget the low end if it's not for broadcast?

And am I right in thinking that for PAL DVD I don't need to limit at all? If I should, then what values are recommended?

Thanks!

Nick

If you shot DV, there might be a little bit of stuff under 16. Digital black level should be at 16, and I think DV compression will push some pixels under 16. So if you clip those, it's good because you know anything under 16 is erroneous anyways.

Many/all DV cameras record stuff over 235 (digital white level). You can deal with it different ways...
If you want to keep all the >235 detail, add the color corrector and set gain to 0.920, offset to 0.8. If you do this to shots without illegal whites, you'll make the image darker and reduce contrast a little.

An alternative is to not do the color corrector, but instead use the broadcast colors filter and drag the smoothness slider (for luma max) all the way to the right. Or you can also put the color corrector on with gain = 0.960, offset 0.4 and do the broadcast colors with the smoothness slider.

It's all pretty subjective, so go with what looks best.

And am I right in thinking that for PAL DVD I don't need to limit at all?
I don't know much about PAL, sorry.
I think that the digital white and black levels are still the same... so that'd be 16 and 235 on vegas' histogram.

What would be neat if we could get something akin to "clipping" notifacation in Sound Forge.
What Final Cut Pro does is that its histogram shows illegal white values as red. This would be nice- anything above 235 on Vegas' histogram should be a different color. Maybe pick yellow or green since red might freak some people out.
By looking at the histogram you'd see how much illegal colors you have in your image.

Same deal for colors <16.

At the end of the day, you should still eyeball things. But for certain things, showing illegal values in a different color on the histogram would be useful.

Make a product suggestion please :)

Bear in mind that Vegas works in RGB unlike FCPs YUV space. In RGB land ALL values are legal as are all values in DV land, it's only in analogue land that you hit issues.
Bob.

I can't speak for NTSC but from my experiments with PAL DVDs ignore it, the DVD players keep the analogue outputs withing legal anyway. Start adding BC and it'll end up looking a bit washed out from the DVD player, I'm pretty certain the same goes in NTSC land as well.
VHS is another matter entirely.
Bob.

Thanks for the replies.

Well, for the time being my project is all digital (DVD only).

A 16/16/16 underlaid black track, as suggested by Glenn in other threads to keep fades-to-black correct, looks VERY different from 0/0/0 on my Sony PAL TV, so I'd rather keep the deep darks and not clip the bottom end if poss..

As for the top end, on some clips (e.g. relections off water) I can actually see the loss of detail even by limiting max composite to 133.

I'll have a go at fixing the worst clips with the methods Glenn suggests.

Nick

I think it is wrong to state something like "wrong" colors. If you wish to deliver your production to broadcast, fine. Correct it to 16..235.

If you do not deliver your production to braodcast, it is fine enough to stay with 16..255 (our camcorder does not support superblack, typically). So, from that perspective it makes sense to do nothing - in many cases.

It is an advantage of Vegas that the DV-codec is able to maintain 0..255, and that you are able to apply specific filter, if you wish to stay within 16..235.

Nick,
digital video is no different really to digital audio, for best results you want to use all the dynamic range the 'bits' have to offer. For this reason DV cameras record from 0 to 255. If you're seeing loss of detail in the highlights I'd suggest it's happening in the TV, it's probably out of calibration or by design it's crushing the highlights in the process of making the picture look 'nicer'.
I've been though the exercise of recording bars and greyscale to DVD, playing it back in several DVD players and monitoring the output of the player with scopes. Signals that go in DV land from 0 to 255 end up at 16 to 235 on the composite output of the player. So if you legalise your video to 16 to 235 then you'll get around 28 to 225, that's a pretty big hit in dynamic range.
I've authored around 500 DVDs so far, no legalisation and no problems. However whenever I rarely make VHS tapes I do legalise.
Why?
Well with compsite analogue video when the signal drops below a certain level that's supposed to indicate a sync pulse and some el cheapo TVs can get there knickers in a twist and loose sync, yes I've had this happen, every fade to black and the TV would roll! Now at the other end things aren't quite so dramatic but there can be a porblem with transmitters, feed them over 1 Volt and they MAY overmodulate causing vision to break into the audio, typically heard as buzzing when there's white supers. I think most transmitters today have limiters to stop this happening although one naughty local station got caught out doing this deliberately, going to 1.1Volts to make their vision leap out of the screen.
Now I haven't tried repeating my tests with NTSC DVDs but I suspect the same applies, after all there's no 7.5 IRE setup in NTSC DV.
Bob.

Thanks Bob, this is very encouraging that you've had such success with DVDs without "legalising" them.

What I meant was that by entering 133 as the max value in the composite section of the BC plug-in, I could see the difference on my TV in the bright parts of my video. In other words my Sony PAL TV will show differences in detail between this setting and an unlimited setting. Obviously that dynamic range is something I want to retain for my customers' TVs too, if it's not going to cause a problem. So there's nothing wrong with my TV, it's displaying detail across the full range.

In the past whenever I've made my one-off DVDs for NTSC customers I've always added a bit of "broadcast-colours correction" in Procoder as the NTSC MPEG2 is written, but I never really knew what I was doing. Now I won't even bother doing that.

Nick

Bear in mind that Vegas works in RGB unlike FCPs YUV space. In RGB land ALL values are legal as are all values in DV land, it's only in analogue land that you hit issues.
For DV, black level (for DV) is supposed to be at 16 (Y'/luma value, for 8-bit formats) while white level is supposed to be at 235.
Suppose you print your video onto miniDV and capture into Final Cut Pro. In FCP, all its filters work off black=16 (Y') and white=235 (Y').
In Vegas, filters work off black = 0 (Vegas/RGB) and white = 255 (Vegas/RGB). So for example, when you boost the gain control on the color corrector, black level ends up at the wrong place.

I think I've lost my point here, but you can make illegal values in Vegas.

2- If you use the Microsoft DV codec or other codecs that decode black level to 0 RGB and white level to 255 (instead of 16-235, which Vegas calls studio RGB) then I believe it becomes a lot harder to generate illegal values. You can still generate illegal composite that a broadcaster could reject (but that's only if you need broadcast safe, which is more stringent than other formats like DVD).

*Note about color spaces: DV uses the Y' Cr Cb color space (sometimes confusing called YUV). Y' stores the luma (brightness) information, while Cr stores Y minus red and Cb stores Y minus blue. Your TV ultimately needs voltages for the R, G, and B electron guns. It can figure it out from the Y' Cr and Cb components by adding/subtracting them... Green is figured out from all of the components (algebraically it works).

Vegas decodes Y' Cr Cb into RGB color space. 16 Y' goes to 16 16 16 RGB and 235 Y' goes to 235 235 235 RGB, if using the Vegas DV codec.

3- I've been though the exercise of recording bars and greyscale to DVD, playing it back in several DVD players and monitoring the output of the player with scopes. Signals that go in DV land from 0 to 255 end up at 16 to 235 on the composite output of the player. So if you legalise your video to 16 to 235 then you'll get around 28 to 225, that's a pretty big hit in dynamic range.
Bob, what scopes are you using? (i.e. Vegas scopes, or a hardware vectorscope that you can touch and feel)

From what I've read, some DVD players clip values below digital black level or above digital white level. And some don't.
If you want your footage to be "DVD safe", you should probably keep the values "legal" so that your image won't looked clipped on the DVD players that do clip illegal values.

If you display superwhites, then yeah you do get increased dynamic range. Two downsides are: superwhites cause geometry distortions in CRTs... if your TV goes too bright, lines change their straightness. CRTs don't show lines perfectly straight anyways and the geometry distortion can be subtle, so this may not be a big deal.
The other downside is that CRTs lose brightness as electrons hit the phosphors... pumping out superwhite values will wear their TV out more quickly.


I might be wrong though as I haven't gone out with an external waveform monitor and measured all this stuff and see how things perform in practice.

Glenn,
the geometry issue with whites happens even with legal whites, it's very obvious on my el cheapo 16:9 TV when it's fed 4:3. The problem is poor regulation in the horizontal deflection power supply, the deflection signal also drives the EHT supply. When the EHT draws more current for the whites the horizontal deflection shifts, doesn;t happen with good TVs or monitors. Pushing the whites outside legal is most likely to cause audio breakthrough.

I only ran my tests by recapturing through my ADVC-300 however my results are confirmed by an associate using real scopes. He'd made a DVD of test patterns and immediately discovered all the levels were shifted. Many others here and elsewhere have run the same tests and got the same results. I suspect, but haven't been able to test, that the component outputs from the DVD players don't legalise the video.
Bear in mind that many D->A converters have a legalise function, this is where it should be done, not in digital land.

One trap when you do legalise in Vegas. Add a track of superblack at the bottom of the T/L. Without that Vegas decides the last frame of a fade is 'nothing' and doesn't apply any FXs including BC. Don't add legal black or it'll get shifted by the BC filter off the value you want. I usually add the BC FX to the video bus.
Bob.

Bob, I'm not sure I understand you 100% so I'll ask you this.

Suppose you make a test pattern in vegas with patches of the following colors:
0 0 0 RGB, 0 on Vegas' histogram (A)
16 16 16 RGB, 16 on Vegas' histogram. (B)
235 235 235 RGB, 235 on Vegas' histogram. (C)
255 255 255 RGB, 255 on Vegas' histogram. (D)
Using the Sony DV codec.

My understanding is:
NTSC, not Japan
(A) will end up below 7.5IRE, possibly at 0IRE. Some DVD players will put A at 7.5IRE.
B will end up at 7.5IRE.
C will end up at 100IRE
D will end up at ~110IRE

for PAL:
B should end up at 0mV (PAL' black level).
C should end up at 700mV (PAL's white level).
D should be above C, or the same as C depending on DVD player.
A should end up below B or the same as B, depending on DVD player.

Pushing the whites outside legal is most likely to cause audio breakthrough.
If their TV is hooked up to the DVD player via RCA or Svideo or component, this won't happen?

If their TV is hooked up to their VCR to their DVD player via UHF/VHF, the audio buzzing can happen?

Just did a test in Vegas.

On my Noma DVD player (NTSC):
A and B end up as the same color.
C and D end up as the same color.
Fed the DVD player into my Sony PVM1354Q... other input was my camcorder, fed from Vegas with the same thing.

That indicates clipping happening somewhere along the line. I think the DVD player clips illegal values.

It could be that DVDArchitect clips illegal values, but I can drop the MPG I encoded into Vegas and I see all the values.

I've taken the encoded file back into Vegas and the levels read the same! It's definately the players doing this. No they don't clip, they compress all the values, that's the proper way to do it anyway. This means that anything around the mid point (128) isn't affected.
Note also there is NO setup on NTSC DV, that ONLY applies in analogue land, my ADVC-300 has a switch that optionally lets me add 7.5 IRE setup for PTT and I think remove it when I capture, not that I do that much NTSC stuff!
Bob.

bob, I was looking at the values on my broadcast monitor and I saw that (A) and (B) were the same colors, as in they were merging with each other. In this case it doesn't seem like the DVD player was "compressing" things into legal range (i.e. putting 0-255 vegas rgb into 0/7.5-100IRE) but rather it was clipping the superblack and superwhite values.

To do your own test:
Drop the color bars pattern on a timeline. Add a solid color of 255 255 255 RGB. Use the masking tool so you only see a little square. Make sure part of it touches the 100% white bar in the bottom left.

Export a mpeg2 and put that into DVD Architect and burn a single movie CD.

Hook that up to your monitor. Pump brightness and contrast - do you see the leftmost PLUGE bar? I don't. Apparently, some DVD players can output that leftmost PLUGE bar.
Put those settings back to normal. Look at the 100% white bar- does it merge with the 255 255 255 RGB square you made in Vegas?

You can also hook up your camera too, and see what colors bars look like. You should see all three PLUGE bars.