Creating animated AVI's in Vegas with Transparency.

Liam_Vegas wrote on 10/18/2004, 6:14 PM

OK.... On the face of it I think this <should> be simple... but I just cannot see how to do this.

I am trying to create some simple animated lower third loop within Vegas... so that I can re-use the loop in other videos.

Let me see if I can explain the problem.

Within one Veg I have my animated sequence working <just perfectly> overlayed over some existing video. What I want to do now is to switch off the underlying video track and then to be able to render the animation tracks in a way that I can then load this back into another Veg and overlay over the top of a video track in that. Get me so far?

Problem is that when I am in the original Veg (where I created the animated loop) and switch off the underlying video track... I end up with a black background. When I render this out as uncompressed AVI (which I know you need in order to get an alpha channel) I of course get a nice black background as well (which renders it useless for what I am trying to do).

So... I guess the problem is due to the default "fade-to" background setting that defines what color the "real" background video is for each project (Options/Preferences/Video/Track fade bottom). By default this is black. I changed it to a setting of "Alpha 0" - which I think should result in a transparent background. It does not appear to work this way.

So... hopefully you understand what I am trying to do.

Anyone know what the trick is? Or.... am I just trying to do something that is not possible?

Thanks for your help.

-Liam
p.s. - I have rendered that "animated" clip from Vegas with the "Alpha Chanell" option selected. When I loaded this uncompressed clip back into vegas I then messed around with the event properties to select various alpha modes (none seemed to work). This makes me think the problem is related to how I originally created the Veg in my "source" project. Any ideas?

Comments

jetdv wrote on 10/18/2004, 6:46 PM

After you pick "Uncompressed" as the AVI format, click on Custom and on the VIDEO tab, make sure the "Render Alpha Channel" box is checked.

Once you add the uncompressed clip to the timeline, right-click it, choose "Properties", go to the second tab, and change the "alpha channel" mode. The area that was black on the original render will now show through. I usually pick "Premultiplied (Dirty)".

Liam_Vegas wrote on 10/18/2004, 6:54 PM

Sorry - should have said this.... I did the "Render Alpha Channel" trick... and I did mess around with the event properties and chose every combination of alpha channel - but didn't seem to help.

Have you done this sort of thing yourself? Or are you applying your logic to how you think it should work?

I am particularly interested in this "Background Setting" thing. How do you get around the fact that by default we have a black background - and what does that setting of the fade-to color mean? Am I using that correctly?

AND if you have indeed done this yourself (GREAT!!! - while I have your attention)... what have I done wrong? Can you (or anyone) send me a Veg that illustrates a simple example of this?

Thanks

-Liam
liam at imagebeam dot com

Chienworks wrote on 10/18/2004, 7:02 PM

I just tried doing one of these and it worked very well. The one thing i did that i didn't see mentioned in this thread is a mask. I created a parent track with a mask showing only the area of the video i wanted to keep (in your case, a white rectangle covering the lower thirds area with black everywhere else). I believe without a mask your alpha channel will end up solid opaque, which is no transparency at all.

p@mast3rs wrote on 10/18/2004, 7:45 PM

I tried to do this however, after I installed SP2 it no longer worked. Do you have SP2 installed?

Liam_Vegas wrote on 10/18/2004, 8:37 PM

Unless I am missing something It's sounds like this mask you created defeats the object of having an AVI with transparency.

Yes - I can create a mask that will allow the video on the lower track to show "around" the outside of the animated video I produced... but in my case the actual animated video itself contains transparency (or at least that is what I am trying to accomplish) and what I want to do is to allow the underlying video to show through this.

And... just to be pedantic here - in case anyone just reads this post and forgets what I posted originally - remember that I can get the animation to work perfectly (just like I descrtibed here) in that original Veg that I used to create the animation.

The problem I am having is purely related to the question of how to save that animation as an AVI that I can use in other vegs and preserve the transparency.

Thanks

nickle wrote on 10/18/2004, 9:12 PM

I just tried it with a bezier mask saved as uncompressed avi with alpha channel.

Then in order to use it (it shows up with a black background) you need to select (media - alpha channel) and put the video you want to use with it (your new veg) under it on the next track and make it the child and select source alpha on the parent. Just what Jetdv and Chienworks said.

Liam_Vegas wrote on 10/18/2004, 9:26 PM

OK... but how did you set the fade-to-background color? did you change that from the default of black? That seems to me to be critical here - but maybe I am I misunderstanding this (I am sure I am).

[EDIT] - and in any case - applying a bezier mask will only work on a complete video layer... in my case (in that original veg) the animation is built up over several tracks... so a bezier mask cannot be applied to this. Again.. I am left thinking that what I am trying to do here is either not possible... or that fade-to-background setting is not working the way I expect it to. The thing that gets me is that even after you change that setting - the backgrounds still look black.. how on earth can you possibly know the background is actually transparent - if it always shows as black?

And... how about tyring to use the bezier mask over the top of a video segment that is set to be semi-transparent? As that is more like what I am trying to do.

I will try this myself anyway... but my guess is that while doing the bezier mask may indeed do the right thing for the bit that is cut-away however the bit of the video that is transparent will be showing through to the background color (that I am still messing up - as I don;t understand this stuff).

I'm not sure "I" understand what I am saying here - so I hope you can all figure it out.

nickle wrote on 10/18/2004, 9:56 PM

I happened to already have the clip I mentioned saved previously with the alpha background.
It is a person walking around. When I put it on the timeline, it was a person walking around in a black clip. It would be nice if the alpha was a checkerboard but it is black.

Then I put a clip of generated solid color on the lower track. (Cyan).

Then by ensuring the top clip was (properties/media/alpha-straight) I just made the solid color a child and used composite mode source alpha on the top track and voila, a person walking around in a cyan background.

No fading to background color or anything else.

You did just render your lower thirds part and not the whole thing right?

Liam_Vegas wrote on 10/18/2004, 10:02 PM

So you already had the clip with the alpha! Well that is one major difference then. I am trying to get to that point. As I said... the bezier mask will not be very useful for me to generate this as it can only be applied to a single video layer (right?).

Also... by having to mess with this child thing - won't I have to make all my lower video tracks a child of this overlayed animation? That seems a little restrictive as well.

WHat I really want is for my animation video to act just like a bit of generated text media. You don't need to do anything special to the text media to make it overlay over all the layers of video below it. No need to make anything a child here. The fact the text media contains alpha information (seems to me) is why the video shows through. I still can't see WHY the child thing should be necessary if the video you have contains the alpha information.

You did just render your lower thirds part and not the whole thing right?

explain what you mean by that? I rendered the entire video frame - no way to (that I know) to somehow render just a part of the video frame?

Liam_Vegas wrote on 10/18/2004, 10:08 PM

For the time being I have implemented a work around.

I rendered my animation loop to an NTSC DV AVI without messing at all with the alpha channel.

Then I load this into my project and create a bezier mask to isolate the animation. I then also set the transparency of this track so that I get the underlyijng video to show through. Now I can duplicate this event - and stretch it to whatever size I want - with the animation looping.

So... in the end I got the result I was looking for but not the way I wanted to. I still want to know how to do it with uncompressed / alpha channel... but I guess I'll have to wait until someone can show me in person what I am doing wrong.

So... thanks to all for the help... I do appreciate it... and if anyone can explain it all to me... I am still here.

-Liam

nickle wrote on 10/18/2004, 10:15 PM

As I understand this, it is the lower thirds that you made with an alpha channel right? So you used a mask of some sort? Then you render it not only to uncompressed avi but you check off the "render alpha channel" in the "custom" dialog?

If you did that, then the black IS the alpha channel. So when you use the parent/child thing, the black is then transparent and whatever is on the other track shows through. Same as the generated text.

Liam_Vegas wrote on 10/18/2004, 10:23 PM

There is "a mask" used on one part of the animation (and it is a lower third). The mask was applied to one of the video layers to isolate a part of an animated background (from the Editors Toolkit). I then overlayed several other tracks over this with some graphical elements that I then animate across this background.

So my question for you is - how does Vegas know the black areas are alpha? Unless you tell it so... why would it make any decision to say any particular area of black in the video is actually transparent? Which is why I believed you must mess with that fade-to-black setting.

nickle wrote on 10/18/2004, 10:45 PM

In my example, the bezier mask is the person walking around. Everything else in the scene turned black when I rendered it to uncompressed with alpha except what was inside the masked area (the person). If vegas made it a checkerboard it would be an obvious transparent area, but vegas makes it black. But because I KNOW I rendered it with an alpha channel, I can use it by right-clicking it and going to properties-media-and selecting "alpha-straight" to tell vegas it has an alpha channel.

Then I use it as I described.

Liam_Vegas wrote on 10/18/2004, 10:53 PM

Hmm... I guess it is finally beginning to sink in. I basically did this (or so I thought) - and it made no difference. I'll try it again sometime and see what happens.

Liam_Vegas wrote on 10/18/2004, 11:01 PM

OK... so I got it to work. No need to mess with that fade to setting. Here is exactly what was needed.

Render to AVI (default template - uncompressed) - make sure the "RENDER ALPHA" is set to yes.
Load this into my other projects and right click the media and select properties/Alpha straight.

No need to set parent/child or to mess with the fade-to setting.

I know that must have seemed like hard work... but thanks for sticking with me until it was drilled in to my poor tired brain. Now gotta go to bed.. need to be up in 5 hours!

-Liam

nickle wrote on 10/18/2004, 11:06 PM

I'm glad I live on the west coast....everyone else has to get to bed before me. (at least in North America.)

Liam_Vegas wrote on 10/18/2004, 11:07 PM

I'm on the west coast too... but I have to be up Reeeeeal early tomorrow!

Grazie wrote on 10/19/2004, 12:52 AM

Liam . . "Render to AVI (default template - uncompressed) - make sure the "RENDER ALPHA" is set to yes. Load this into my other projects and right click the media and select properties/Alpha straight. " . . now I ,must be doing something wrong . . I don't get it!

The ONLY way I can get to select the background colour is for Alpha Channel to be Premultiplied or its Dirty version . . Straight's colour background option is greyed out. In any event I can't get the colour I select to go transparent. . . . hmmm ....
Grazie

jetdv wrote on 10/19/2004, 6:14 AM

Glad to hear you got it working. But the answer to your question is YES, I HAVE gotten it to work with the exact steps I listed in my first post. In fact, I typed the post WHILE doing it to make sure everything would work correctly and, on my system, it DID.

Grazie wrote on 10/19/2004, 7:17 AM

I've repeated the steps and I still can't get it.

G

J_Mac wrote on 10/19/2004, 7:44 AM

Another approach is to install the 'Default Text' from the Gen Media as your background, delete the 'Sample Text" words, and then render as above with the alpha channel. This way you 'install' an alpha background on the uncompressed lower third clip. Any thoughts? John.

Grazie wrote on 10/19/2004, 8:28 AM

Edward thank you for email . . "I'll be back!" . .to yah!

G

Liam_Vegas wrote on 10/19/2004, 3:33 PM

Yep - the thing I was doing worng was messing around with that fade-to setting in the options. If I had left that alone all would have been sweet. Sometimes I can try too hard!

Although I wonder what the difference is between alpha straight and premultiplied (dirty).

Mandk wrote on 10/20/2004, 8:29 AM

I was attempting to render a repeated boris graffitti effect with Alpha Channel to speed ultimate rendering.

This approach worked wonderfully - Thank you Edward and everyone else for the great advice