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

Ruben Pla · September 20th, 2006, 11:20 AM

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

Matthew Chaboud · September 20th, 2006, 01:25 PM

You're using broadcast colors (as you should) to constrain the luma range of your project, but broadcast colors can't affect regions of zero alpha (because it would have to raise the brightness of something that, by definition, has to be completely black). The black bars on your project are zero alpha, so they're slipping past broadcast colors. The event that you are fading with to get a fade to black, on the other hand, was brought in to a project at the target aspect ratio and, thus, fits the target aspect. When you fade down to black, you're actually fading up in alpha in the black bars. This full alpha allows broadcast colors to do what it's supposed to do to every part of the image, instead of just the middle.

When Vegas renders, it hands information with alpha to the file renderer for a given format. Most formats discard that information, but some make use of it. What this means is that this behavior is not likely to change in the future.

But what can you do about it?

The simplest fix is to just 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.

Ruben Pla · September 20th, 2006, 02:09 PM

Thank you very much, Matthew. I appreciate your help.

Ruben

Ruben Pla · September 20th, 2006, 02:17 PM

Matthew,

Someone suggested the following:

The 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.

Which do you think would work better?

Ruben

Matthew Chaboud · September 20th, 2006, 02:59 PM

Ruben,
7.5 IRE setup is what's used for NTSC, but it really just controls what zero means. All of the broadcast colors presets (except for "Cut away section") will restrict blacks to the right range. If you're applying broadcast colors already, the setup value has nothing to do with the bars looking off at fades. It comes down to alpha.

There are a few ways that you can diagnose this problem.

1) In the Video Preview window, turn on the "Alpha as Grayscale" overlay (the button that looks like a strange tic-tac-toe board. You should be able to see where parts of your image go transparent (black boxes). Proper video for final delivery should be completely white, all the time.

2) When you've applied broadcast colors to a project, compare what that project looks like in the Waveform monitor (Video Scopes) to what a test patter generator set to "Pluge and Porches" in an otherwise empty project looks like in the Waveform monitor. Set your Waveform monitor to Luminance and look at the reading for the test pattern. You'll see a line at 7.5 that goes all the way across. That line should be as dark as anything gets in your final delivery project.

-Matt

Ruben Pla · September 20th, 2006, 04:31 PM

Matt,

Creating a solid-black track before the main video track won't darken the look of the film in any way, will it?

Ruben

Matthew Chaboud · September 20th, 2006, 05:08 PM

You mean under it, right? Solid black won't look any different to you or me than zero alpha black, but it will look different to the filter. All of your bars will look "gray," even though that 7.5 level should be used as the point for black on your display monitor (if properly calibrated).

You should be safe in doing this. If you had alpha bleed before, you'd still have it composite over the same black that you did before adding this, so it doesn't make a visual difference.

Ruben Pla · September 20th, 2006, 05:16 PM

Matt,

Yes, I meant "under." Sorry. I tried generating a solid-black track but the black bars still shows up gray during the fadeout on the DVD. Just to double check, I created a new track (one row under the main video track), created a solid-black generated effect, and rendered it that way. If that's correct, it didn't work. Is there something else I need to do?

Thank you,

Ruben

Matthew Chaboud · September 20th, 2006, 10:05 PM

The way to check is to show the alpha channel as grayscale before you add the new black event to make sure that alpha showing through is the problem. You could also have an odd FX chain or something else that I can't see since I can't see your project.

The most common cause for this is definitely alpha show-through, but it's possible that you have something else going on.

Ruben Pla · September 21st, 2006, 01:26 PM

Matt,

I did as you recommended below:

"In the Video Preview window, turn on the "Alpha as Grayscale" overlay (the button that looks like a strange tic-tac-toe board. You should be able to see where parts of your image go transparent (black boxes). Proper video for final delivery should be completely white, all the time."

and the full screen is white the whole time. What does this mean and what should I do next?

Thank you,

Ruben

Matthew Chaboud · September 22nd, 2006, 03:03 PM

Without being able to see the project and the individual media, I can't be sure. Watch your scopes. If the waveform level never dips below 7.5 on the monitor, then it's your preview monitor (or a bug in DVD authoring, but that is highly unlikely at this point). It's possible to have contrast that is too great on monitors, giving a sense of overbrightness.

Basically, the next step is to spot check the scopes when you see this problem and make sure that everything is constrained properly.

Ruben Pla · September 22nd, 2006, 06:58 PM

Matt,

It's ok. It turns out that it was because I was (intentionally) rendering parts of my scenes PAST where the video ended on the Vegas timeline (extended by music tracks), to give myself a longer blackout after the fades. I should have been using a 16, 16, 16 generated black card instead.

That did the trick.

Take care,

Ruben

September 20th, 2006, 11:20 AM	#1
Ruben Pla Regular Crew Join Date: Mar 2005 Location: Los Angeles, CA Posts: 80	Black Bars at top and bottom of screen FADE OUT... 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

September 20th, 2006, 01:25 PM	#2
Matthew Chaboud Regular Crew Join Date: Sep 2006 Location: Chicago, IL, USA Posts: 93	Here's what happened: You're using broadcast colors (as you should) to constrain the luma range of your project, but broadcast colors can't affect regions of zero alpha (because it would have to raise the brightness of something that, by definition, has to be completely black). The black bars on your project are zero alpha, so they're slipping past broadcast colors. The event that you are fading with to get a fade to black, on the other hand, was brought in to a project at the target aspect ratio and, thus, fits the target aspect. When you fade down to black, you're actually fading up in alpha in the black bars. This full alpha allows broadcast colors to do what it's supposed to do to every part of the image, instead of just the middle. When Vegas renders, it hands information with alpha to the file renderer for a given format. Most formats discard that information, but some make use of it. What this means is that this behavior is not likely to change in the future. But what can you do about it? The simplest fix is to just 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.

September 20th, 2006, 05:08 PM	#7
Matthew Chaboud Regular Crew Join Date: Sep 2006 Location: Chicago, IL, USA Posts: 93	Nope. You mean under it, right? Solid black won't look any different to you or me than zero alpha black, but it will look different to the filter. All of your bars will look "gray," even though that 7.5 level should be used as the point for black on your display monitor (if properly calibrated). You should be safe in doing this. If you had alpha bleed before, you'd still have it composite over the same black that you did before adding this, so it doesn't make a visual difference.

September 22nd, 2006, 03:03 PM	#11
Matthew Chaboud Regular Crew Join Date: Sep 2006 Location: Chicago, IL, USA Posts: 93	Well, without seeing the project.. Without being able to see the project and the individual media, I can't be sure. Watch your scopes. If the waveform level never dips below 7.5 on the monitor, then it's your preview monitor (or a bug in DVD authoring, but that is highly unlikely at this point). It's possible to have contrast that is too great on monitors, giving a sense of overbrightness. Basically, the next step is to spot check the scopes when you see this problem and make sure that everything is constrained properly.

September 20th, 2006, 02:09 PM	#3
Ruben Pla Regular Crew Join Date: Mar 2005 Location: Los Angeles, CA Posts: 80	Thank you very much, Matthew. I appreciate your help. Ruben

September 20th, 2006, 02:17 PM	#4
Ruben Pla Regular Crew Join Date: Mar 2005 Location: Los Angeles, CA Posts: 80	Matthew, Someone suggested the following: The 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. Which do you think would work better? Ruben

September 20th, 2006, 02:59 PM	#5
Matthew Chaboud Regular Crew Join Date: Sep 2006 Location: Chicago, IL, USA Posts: 93	Ruben, 7.5 IRE setup is what's used for NTSC, but it really just controls what zero means. All of the broadcast colors presets (except for "Cut away section") will restrict blacks to the right range. If you're applying broadcast colors already, the setup value has nothing to do with the bars looking off at fades. It comes down to alpha. There are a few ways that you can diagnose this problem. 1) In the Video Preview window, turn on the "Alpha as Grayscale" overlay (the button that looks like a strange tic-tac-toe board. You should be able to see where parts of your image go transparent (black boxes). Proper video for final delivery should be completely white, all the time. 2) When you've applied broadcast colors to a project, compare what that project looks like in the Waveform monitor (Video Scopes) to what a test patter generator set to "Pluge and Porches" in an otherwise empty project looks like in the Waveform monitor. Set your Waveform monitor to Luminance and look at the reading for the test pattern. You'll see a line at 7.5 that goes all the way across. That line should be as dark as anything gets in your final delivery project. -Matt

September 20th, 2006, 04:31 PM	#6
Ruben Pla Regular Crew Join Date: Mar 2005 Location: Los Angeles, CA Posts: 80	Matt, Creating a solid-black track before the main video track won't darken the look of the film in any way, will it? Ruben

September 20th, 2006, 05:16 PM	#8
Ruben Pla Regular Crew Join Date: Mar 2005 Location: Los Angeles, CA Posts: 80	Matt, Yes, I meant "under." Sorry. I tried generating a solid-black track but the black bars still shows up gray during the fadeout on the DVD. Just to double check, I created a new track (one row under the main video track), created a solid-black generated effect, and rendered it that way. If that's correct, it didn't work. Is there something else I need to do? Thank you, Ruben

September 20th, 2006, 10:05 PM	#9
Matthew Chaboud Regular Crew Join Date: Sep 2006 Location: Chicago, IL, USA Posts: 93	The way to check is to show the alpha channel as grayscale before you add the new black event to make sure that alpha showing through is the problem. You could also have an odd FX chain or something else that I can't see since I can't see your project. The most common cause for this is definitely alpha show-through, but it's possible that you have something else going on.

September 21st, 2006, 01:26 PM	#10
Ruben Pla Regular Crew Join Date: Mar 2005 Location: Los Angeles, CA Posts: 80	Matt, I did as you recommended below: "In the Video Preview window, turn on the "Alpha as Grayscale" overlay (the button that looks like a strange tic-tac-toe board. You should be able to see where parts of your image go transparent (black boxes). Proper video for final delivery should be completely white, all the time." and the full screen is white the whole time. What does this mean and what should I do next? Thank you, Ruben

September 22nd, 2006, 06:58 PM	#12
Ruben Pla Regular Crew Join Date: Mar 2005 Location: Los Angeles, CA Posts: 80	Matt, It's ok. It turns out that it was because I was (intentionally) rendering parts of my scenes PAST where the video ended on the Vegas timeline (extended by music tracks), to give myself a longer blackout after the fades. I should have been using a 16, 16, 16 generated black card instead. That did the trick. Take care, Ruben