Saving Green screen file with alpha channel at DVinfo.net

Go Back   DV Info Net > Windows / PC Post Production Solutions > What Happens in Vegas...

What Happens in Vegas...
...stays in Vegas! This PC-based editing app is a safe bet with these tips.


Reply
 
Thread Tools Search this Thread
Old March 20th, 2012, 08:52 PM   #1
Trustee
 
Join Date: Jul 2007
Location: New Zealand
Posts: 1,104
Saving Green screen file with alpha channel

Not sure if the thread title is correct...

Applying Chroma Key and other additional FX to a track uses a lot of computing power. Is it possible to render a track with the Chroma Key etc applied and retain the 'see-through' effect in the rendered file?

I have graphics I need to insert between the CK subject and the background but would like the CK out of the way so the computer doesn't choke on all the FX going on...

I have four tracks which all need to be CK'd...
Renton Maclachlan is offline   Reply With Quote
Old March 21st, 2012, 12:19 AM   #2
Jubal 28
 
Join Date: Mar 2005
Location: Wilmington, NC
Posts: 872
Re: Saving Green screen file with alpha channel

I believe you can only do it in uncompressed AVI.

Though I haven't tried it for some time and some other new format may be able to do it.
David Jimerson is offline   Reply With Quote
Old March 21st, 2012, 02:14 AM   #3
Trustee
 
Join Date: Oct 2009
Location: Central Coast Australia
Posts: 1,008
Re: Saving Green screen file with alpha channel

From Vegas it will be a pain,
Uncompressed 1080p gives you about 1.93GB per 10 sec.
Quicktime PNG may be a better option at around 145MB per 10 sec, but it renders very slow.
Lagarith RGBA is great, but Vegas wont export the alpha channel, it ends up Premultiplied.
If you have After Effects or Premier Pro try Lagarith RGBA, might even be worth downloading a trial just to render out your files, Prob faster than waiting for the PNG's to render, lol.
__________________
http://vimeo.com/livewebvideo
Gerald Webb is offline   Reply With Quote
Old March 21st, 2012, 06:03 AM   #4
Trustee
 
Join Date: Jul 2007
Location: New Zealand
Posts: 1,104
Re: Saving Green screen file with alpha channel

Thanks guys.

It appears it can't reasonably be done...so I have to devise a workflow that can accomodate the Chroma key without slowing my system down too much.

I have 13 sessions of 15 > 30 minutes which each have four cameras needed to be chroma keyed. I will be switching between cameras but at this point do not know where the switching will occur...and will not know untilI have my graphics in place etc.

I was hoping to do each session in one .veg file, but it seems like this will not work - and that I will need to do each camera in a separate file and bring them together later on somehow...

Just trying out Boris chroma key...seems pretty good...

hmmm...
Renton Maclachlan is offline   Reply With Quote
Old March 21st, 2012, 08:50 AM   #5
Major Player
 
Join Date: Jun 2008
Location: Milwaukee WI
Posts: 626
Re: Saving Green screen file with alpha channel

Hi Renton,

You might try the Matrox MPEG-2 I-Frame + Alpha codec (HD version also available).

Can be downloaded here: Matrox Video - Support - Driver Downloads

Under "Products" column, scroll all the way to the bottom to find "Matrox VfW codecs".

Thanks

Jeff Pulera
Safe Harbor Computers
Jeff Pulera is offline   Reply With Quote
Old March 21st, 2012, 12:25 PM   #6
Inner Circle
 
Join Date: Sep 2003
Location: Portland, Oregon
Posts: 3,259
Re: Saving Green screen file with alpha channel

I've been unable to use Lagarith alpha out of vegas too.

QT Animation at "millions +" works fine for cross-platform, but windows QT preview/render performance is too irritating for me to make editing decisions.

I have had to go uncompressed AVI.

Supposedly the Avid DNxHD codecs can support alpha, but they run in the slow QT wrapper, I've not tried to make that work.

I'm very interested to try the matrox codecs, thanks for the link, Jeff.
__________________
30 years of pro media production. Vegas user since 1.0. Webcaster since 1997. Freelancer since 2000. College instructor since 2001.
Seth Bloombaum is offline   Reply With Quote
Old March 21st, 2012, 01:57 PM   #7
Trustee
 
Join Date: Jul 2007
Location: New Zealand
Posts: 1,104
Re: Saving Green screen file with alpha channel

Hi Jeff

Thanks for that link.

I know nothing about codecs...and am not even sure of the questions to ask regarding them...I've never been this way...

This one you refer to...

How big are the files produced by it?
What is the quality of the files compared with the conventional avi files that come off my SD panasonic GS cameras? This work will evetually be put on DVD and marketed for sale...I want to minimise loss of quality along the production track...
Are these files compatible with Vegas?
Does this condec, once downloaded, go into the render list in Vegas to be selected when desired?
Ummm...any more things I should ask?
Renton Maclachlan is offline   Reply With Quote
Old March 21st, 2012, 06:05 PM   #8
Trustee
 
Join Date: Jul 2007
Location: New Zealand
Posts: 1,104
Re: Saving Green screen file with alpha channel

I downloaded that codec but can't see how to use it in Vegas...
Renton Maclachlan is offline   Reply With Quote
Old March 21st, 2012, 09:42 PM   #9
Inner Circle
 
Join Date: Sep 2003
Location: Portland, Oregon
Posts: 3,259
Re: Saving Green screen file with alpha channel

I've not yet dealt with this codec in particular, but here's how it generally goes:
1) You install a codec using whatever installer the codec maker supplies.
2) Sometimes you have to restart your computer, but the installer might not include this info.
3) You start Vegas and select something to render.
4) Select video for windows, and select the "custom" button. Look through the list of encoders for your new codec.
5) Finding the new codec selection, you then click the "configure" button and try to figure out what the parameters are. If you don't understand them, you leave them alone and hope the default is what you wanted.
6) Render! Review!

If you don't see your new codec in step 4, select Quicktime instead, and then look through that list of encoders.

Usually, free codecs will be wrapped in AVI or QT...
__________________
30 years of pro media production. Vegas user since 1.0. Webcaster since 1997. Freelancer since 2000. College instructor since 2001.
Seth Bloombaum is offline   Reply With Quote
Old March 22nd, 2012, 01:29 AM   #10
Trustee
 
Join Date: Jul 2007
Location: New Zealand
Posts: 1,104
Re: Saving Green screen file with alpha channel

Thanks Seth...tried all that...rebooted...looked in vegas and found it under 'Customise Template'.

I had 'Video for windows (*.avi) > PAL DV Widescreen' selected then in 'Customise Template' chose under 'Video Format', 'Matrox MPEG-2 I-Frame plus alpha'...('Render Alpha Channel' was not selectable...) and rendered....

Unfortunately the transparency was not retained...

...bother.

Anyone have any other ideas...
Renton Maclachlan is offline   Reply With Quote
Old March 22nd, 2012, 04:03 AM   #11
Trustee
 
Join Date: Oct 2009
Location: Central Coast Australia
Posts: 1,008
Re: Saving Green screen file with alpha channel

Just out of interest,
When you re imported your new clip, did you right click, properties, alpha channel,
Change from None to Straight unmatted?
__________________
http://vimeo.com/livewebvideo
Gerald Webb is offline   Reply With Quote
Old March 22nd, 2012, 04:21 AM   #12
Trustee
 
Join Date: Jul 2007
Location: New Zealand
Posts: 1,104
Re: Saving Green screen file with alpha channel

Gerald. No I didn't...but I've just tried that and it still isn't transparent.

I take it by 'import' you mean 'drop on the time line'...after making the change you suggest...
Renton Maclachlan is offline   Reply With Quote
Old March 22nd, 2012, 04:49 AM   #13
Trustee
 
Join Date: Oct 2009
Location: Central Coast Australia
Posts: 1,008
Re: Saving Green screen file with alpha channel

Yes Renton, by import, I just meant "bring into Vegas" however it is done.
So it appears your Matrox codec suffers the same as Lagarith, in that, Vegas cant save the alpha channel.
To confirm, you could try saving to the Matrox codec in another NLE and see if the alpha channel works correctly from there.
For instance, I can save lagarith with alpha channel from After Effects but not Vegas.
As slow as it is, Quicktime PNG may be the best option for you.
__________________
http://vimeo.com/livewebvideo
Gerald Webb is offline   Reply With Quote
Old March 22nd, 2012, 07:34 AM   #14
Sponsor: JET DV
 
Join Date: Dec 2001
Location: Southern Illinois
Posts: 7,873
Re: Saving Green screen file with alpha channel

I know when you render to uncompressed there's a checkbox you MUST check in order to include the alpha channel information. Is there a checkbox that hasn't been checked?
__________________
Edward Troxel [SCVU]
JETDV Scripts/Excalibur/Newsletters
Edward Troxel is offline   Reply With Quote
Old March 22nd, 2012, 01:25 PM   #15
Trustee
 
Join Date: Jul 2007
Location: New Zealand
Posts: 1,104
Re: Saving Green screen file with alpha channel

I won't be able to pursue this for a few days as I'm going away.

If the only way you can render transparency is through uncompressed huge files, then it seems like it is not an option for me...
Renton Maclachlan is offline   Reply
Reply

DV Info Net refers all where-to-buy and where-to-rent questions exclusively to these trusted full line dealers and rental houses...

Professional Video
(800) 833-4801
Portland, OR

B&H Photo Video
(866) 521-7381
New York, NY

Z.G.C.
(973) 335-4460
Mountain Lakes, NJ

Abel Cine Tech
(888) 700-4416
N.Y. NY & L.A. CA

Precision Camera
(800) 677-1023
Austin, TX

DV Info Net also encourages you to support local businesses and buy from an authorized dealer in your neighborhood.
  You are here: DV Info Net > Windows / PC Post Production Solutions > What Happens in Vegas...

Thread Tools Search this Thread
Search this Thread:

Advanced Search

 



Google
 

All times are GMT -6. The time now is 02:46 AM.


DV Info Net -- Real Names, Real People, Real Info!
1998-2017 The Digital Video Information Network