Black Bars at top and bottom of screen FADE OUT...

R

Ruby Tuesday

Active member
Hi,

My film is edited on Vegas 5. It was shot as 24P Anamorphic (squeeze mode.) I rendered it as NTSC DV Widescreen 24P (2-3-3-2 pulldown) and burned it to disk on DVDA 2 as NTSC Widescreen (720 x 480).

When I view it on my TV, it has the Black Bars at the top and bottom of the screen, EXCEPT when there is a FADEOUT between scenes...then the Black Bars fade to a lighter grey.

Does anyone know how to fix this?

Thank you,

Ruben
 
That's because your video is displaying black at 0 IRE and your TV is displaying it at 7.5 IRE (and that's why the bars look grey in comparison). You can use the broadcast colors filter to apply a 7.5 IRE to your video.
 
Thank you for your advice. I appreciate it.

Somebody mentioned doing the following:

Create a new track underneath everything and put a black solid-color generator on that track for the duration of your project. It will make sure that every pixel starts out solid alpha, but black.

Which do you think would work better, your idea or that one?

Ruben
 
If it was rendered anamorphic, there shouldn't be any black bars generated by anybody except the DVD player/TV. Yes? No?

I thought the bars would only be your responsibility if you're making a cropped version.

That sounds more like there is other footage mixed in that isn't native anamorphic.

Or am I completely wrong here? I've never seen this happen.

That being said, yes, put a black track "under" everything else to make the fades better.
 
Adding a broadcast colors effect (7.5 setup) to your project will not help by itself. Anyplace where there's a fadeout and the empty track is revealed (black) will still be rendered as 0 IRE. It will, however, conform the blacks in your actual video to 7.5 IRE.

The black card will work, but the RGB values of the card need to be set to 16, 16, 16. Alpha, 255.

Slight correction, too -- it's not the TV that's the issue; it's the DVD player. The player generates the black bars at 7.5 IRE; the TV displays whatever is fed to it. That's why you can see the difference. If the TV did an automatic boost to 7.5 IRE with any black, it wouldn't be an issue.

Also, DVD players do not automatically add setup (7.5 IRE) to your image. They only generate 7.5 IRE letterbox bars. This, too, is why you can see the contrast; if it added setup to everything, you wouldn't see a difference.
 
I don't think the broadcast colors filter does or should add 7.5 IRE setup. EDIT: See next post.

2- If you add a solid color generator of 16 16 16 RGB (in Vegas), this may prevent the problem of the bars getting darker. Video footage will have blacks at 16 16 16 RGB (if using the default Vegas DV codec), while the background color in Vegas is 0 0 0 RGB (always). You can change this by doing the workaround of adding the solid 16 16 16 RGB black.

Your problem seems to be the opposite though- perhaps your TV has some sort of auto-gain control, and black level isn't calibrated correctly??? Plasma displays for example do need an auto-gain control I believe.

3- In Vegas, you could measure the color of your blacks (this will only give you the R'G'B' units though). Use the gradient map filter, and disable it. use the eyedropper to measure colors.
 
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glenn chan said:
I don't think the broadcast colors filter does or should add 7.5 IRE setup. The setting is there to calculate whether or not the color is illegal.
Click to expand...
It does. This is the effect added (globally) on a 0 IRE black card:

1158790893.jpg



Your problem seems to be the opposite though- perhaps your TV has some sort of auto-gain control, and black level isn't calibrated correctly??? Plasma displays do have an auto-gain control built in I believe.
Click to expand...
The problem is actually an optical illusion. The black bars don't fade or change their black values at all -- they're just contrasting against the 0 IRE black of the video after it fades. Any other time, against other colors, the blacks look "black" and not grey. But they don't change at all.
 
It does. This is the effect added (globally) on a 0 IRE black card:

Hmm it looks like I made a faulty assumption in my last post, although my point does still stand (albiet my original explanation/description was erroneous).

The "7.5 IRE setup" checkbox in the BC filter affects what values will be clipped/limited. I wouldn't call clipping of black level "adding setup".
You can check for yourself by adding the Color Gradient preset "Linear White to Black" and applying some of the Broadcast Colors presets.

2- There's still no such thing as IRE levels in Vegas. The actual IRE levels coming off an analog signal will be affected by the digital-->analog convertor you're using.

3- Explanation of what the Broadcast Colors filter does:

In the Vegas world, there are a few relevant color spaces.

Studio RGB: Black level at 16 16 16 R'G'B', white level at 235 235 235 R'G'B' (digital units).

Computer RGB: Black level at 0 0 0 R'G'B', white level at 255 255 255 R'G'B' (digital units).

DV codecs will decode to either studio RGB or computer RGB. The Vegas default codec will decode to studio RGB. Most Vegas filters however assume computer RGB color space.

DV codecs convert between Y'CbCr color space (which is what DV uses) and R'G'B' color space (which is what Vegas uses).

For Y'CbCr color space, proper black level should be at 16 (Y') and white level at 235 (Y'). The Y' channel (luma) roughly represents the brightness of an image.

DV devices (and other devices) convert between Y'CbCr color space and analog composite formats. In these analog composite formats, the unit "IRE" is used for the analog voltages.

For NTSC (except for Japan), black level should be at 7.5 IRE. White level at 100 IRE.
For Japanese NTSC, black level should be at 0 IRE. White level at 100 IRE.
Similarly for PAL, black level should be at 0 IRE. White level at 100 IRE.

When NTSC is broadcasted, there are transmission limits that places further restrictions on the signal. The NTSC signal is broadcasted with the chroma and luma mixed into one signal (the color is carried via the color subcarrier). The two combined signal is the composite signal. The NTSC spec is designed with limits on the composite signal, from -20 to 120 IRE. The broadcaster may impose further restrictions on these limits (for various other reasons).

In Vegas, you want to make sure that your R'G'B' values don't end up producing illegal composite values. To do this however, Vegas needs to know the following three things:
A- The DV codec's color space. The "Studio RGB (16 to 235)" checkbox is your way of telling the BC filter this.
B- What the D-->A converter does in converting Y'CbCr to analog composite. Does the converter convert *digital* black level to 0 IRE or 7.5 IRE? This is what the "7.5 IRE setup" checkbox (not luma min) determines.
C- What analog composite values you are aiming for. The luma min and max and chroma max and composite min and max settings determine this.

--The luma min and max settings should correspond to your TV standard. 0 and 100 for PAL, Japanese NTSC. 7.5 and 100 for other NTSC.
--Composite min and max are determined by the broadcaster.


The 7.5 IRE setup setting is weird and tricky... it can compensate for equipment doing non-standard conversions. This can be a bad idea since it gaurantees your digital levels will be *non-standard*. Non-standard digital levels going through an improper D-->A conversion can result int the correct levels. The inherent problem is: Do two wrongs make a right?
***To get proper digital levels in the BC filter, the 7.5 IRE setup checkbox should correspond to luma min. If you pass proper digital levels into a proper D-->A (which the broadcaster has), you will have proper analog composite values when broadcast.

The non-standard conversion from Y'CbCr to analog composite:
In a lot of consumer and prosumer DV equipment, the equipment will improperly convert digital black level (Y'=16) to 0 IRE. While this is correct for Japanese NTSC, this is incorrect for NTSC everywhere else. Yet a lot of equipment sold in North American markets will do an improper conversion, putting analog black level at 0 IRE instead of the proper 7.5 IRE.
Now outside of the BC filter, you could potentially tweak the black level to a non-standard level in a way that it'll produce the right analog black level (i.e. when your digital black level is at 32 Y'). For example, the Sony PD150 camera can be set to do this. If you play out of Vegas into the PD150 (or other camera that does non-standard conversions) onto an analog master, then your analog black level will be correct. Unchecking the "7.5 IRE setup" would allow the BC filter to do the right thing for this very non-standard conversion.
But you should probably really avoid this... one of the reasons is that effects may not render correctly since your input color space is wrong.
 
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But there IS IRE once it leaves Vegas and is played by a DVD player. I'm not being technically perfect in what I'm saying in terms of Vegas, but as a practical matter, I'm trying to be as understandable as possible.

0,0,0 in RGB space is the digital equivalent of 0 IRE; 16, 16, 16 is the digital equivalent of 7.5 IRE.

Once it gets to the TV screen from the DVD, it's appropriate to speak of 0 IRE and 7.5 IRE in terms of why the blacks don't match, so I took a shortcut for clarity.

Where the Broadcast Colors filter should help, too, is if there's something black in the video, like a car or a shirt or the night sky or something else which would be darker than the DVD player's bars. It should even out the difference between them as well. (Studio RGB should do this, too.)
 
Ruben,

Is your problem this (I think I misunderstood it the first time):

Imagine the image is broken up into three "rows". The top and bottom rows are the letterbox mask/"black".
The middle row is where the movie goes.

When the movie fades to black, the top and bottom rows appear as a greyish color in comparison to the movie.


If that is the case, then does adding a new layer with a solid color generator of 16 16 16 RGB underneath solve it??
 
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0,0,0 in RGB space is the digital equivalent of 0 IRE; 16, 16, 16 is the digital equivalent of 7.5 IRE.

That can be confusing because it's not always true. i.e. you use the wrong codec, your DV device does non-standard conversions, or you're working PAL.

Perhaps a simple + accurate approach would be to focus on accurate digital levels.
With *default* Vegas, 16 16 16 RGB = proper digital black level. 0 0 0 RGB = improper.
It doesn't matter if you have a non-standard DV device or if you're working in PAL land. And it excludes the wrong DV codec too, because I said default Vegas. :D
 
Well, if you're working in PAL (or non-North American NTSC), you're not worried about 7.5 IRE at all, but fair enough.

I'd say that the "proper" and "improper" black level is contextual, though. What did you have in mind there?
 
I suppose it would mean:
It results in standard levels for the resulting Y'CbCr values.

The digital video standards define black level at 16 (Y') and white level at 235 (Y'). So proper = follows standards.
 
No, I don't mean broadcast standards (although I don't think there are necessarily any broadcast standards when it comes to NTSC broadcast master formatting + composite video levels).

By standards, I mean like ITU-R BT. Rec. 601 and Rec. 709. Proper digital levels are pretty much standardized... black level at Y' = 16, white level at Y' = 235. The only exception is cameras which can record fake setup, like the PD150. Doing that is pretty oddball and I would consider it non-standard.
 
But ITU-R BT.601 or .709 don't matter if you're encoding for the web. They are digital television standards. That's what I meant by "contextual."

There's an argument to be made that you might as well conform all of your video to the standard. That's a ripe discussion.

Anyway, this has gone pretty far afield from the original question in the thread.
 
Dear David & Glenn,

Thank you for the very informative lesson.

One thing I think I should clear up:

The gray of the top and bottom bars are not in comparison to the level of blackness of the "middle" bar (where the video is.) When I view the film on the TV, I can actually SEE the top and bottom bars get gray when there's a fadeout (or in the beginning fadeup and ending fadeout of the film.)

So, it's not a matter of intesity of blackness compared between the two, the bars actually "gray up" when there is no picture, and we have just black (and there are no FX there, either.)

What do you think?

Ruben
 
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