Multiple renders, etc

[Renton Maclachlan]

Originally Posted by Leslie Wand

you can render transparency to a codec that has an alpha channel: mov, huffyuv, and others.

big files usually

wait a minute.... you rendered c'key WITHOUT a background!? what we're you expecting to see? a transparency grid like photoshop?

I was hoping to render the transparency so I could be done with the chromakeying - along with the colour correction - and insert an image later - and so I could stop my system being slowed down by all these FXs...

I would prefer not to have to choose my image at this stage.

[Leslie Wand]

ah, i see......

use an alpha channel codec - and expect very large file size.

i've never gone this route - it seems like a more work and pain than just getting it set up on the tl and working with it there.....

what is your system?

if it's bad with what you're doing i don't think (i might be wrong!) that it would be in any way better with an uncompressed alpha codec and bkgrd, etc.,

ymmv

[Renton Maclachlan]

Thanks Leslie. Perhaps I will just have to render out the colour correction and do the CK later. Or perhaps I need to do my thinking about background images sooner rather than later...

[Renton Maclachlan]

If I go to 'Render as' then 'Custom', a dialogue box opens withdown the bottom 'Render alpha channel (uncompressed video formats only). Above that about in the middle of the dialogue box is a drop down box headed 'Video format'. I have had 'PAL DV Widescreen'.

However if in that box after pulling down the drop down panel, I put 'uncompressed', then the 'Render Alpha Channel' tick box becomes live.

Only the 'Frame size' drop down box turns to 'PAL DV/Std (730x 576)' though the 'Pixel Aspect ratio stays 1.4568.

Would this do the trick?

[Leslie Wand]

sorry really don't know - it's not, asd i mentioned, a route i have ever thought about.

my only experience of alpha channel has been pretty much restricted to graphics and animation - usually in the form of png or tga sequences.

[Edward Troxel]

Yes you can render out the transparency. And when you bring it back in, you can then put it over other footage which will appear in the transparent area. After adding back to the timeline, you may need to right-click it, choose "Properties", go to the "Media" tab, and then change the alpha channel mode.

While extremely huge, rendering out to uncompressed AVI will work. Just open the "Custom" settings and make sure transparency is turned ON. A PNG sequence should work fine as PNGs will save out transparency. I know some Quicktime formats will also do this. If the area is small enough, I'd just try uncompressed AVI.

[Renton Maclachlan]

Originally Posted by Edward Troxel

Yes you can render out the transparency. And when you bring it back in, you can then put it over other footage which will appear in the transparent area. After adding back to the timeline, you may need to right-click it, choose "Properties", go to the "Media" tab, and then change the alpha channel mode.

While extremely huge, rendering out to uncompressed AVI will work. Just open the "Custom" settings and make sure transparency is turned ON. A PNG sequence should work fine as PNGs will save out transparency. I know some Quicktime formats will also do this. If the area is small enough, I'd just try uncompressed AVI.

Thanks Edward. When you say, 'uncompressed avi is huge', what do you mean? I thought that I was already dealing with uncompressed avi!

If I'm not, what sort of size difference in files could be expected?

Leslie: I'm going to be dealing later on with graphics with an alpha channel being brought in from Adobe Illustrator through Photoshop. So far I've only done a very minimal playing around with that aspect of the job - only to confirm that it can be done - and to check out the fact that Photoshop layers can be brought into Vegas, which is really neat. I'm not aware that Illustrator files can be brought into Vegas so I need that other step through Photoshop...

[Edward Troxel]

DV is NOT uncompressed. DV will get you about 13Gig / hour. Uncompressed will be closer to 60-65Gig / hour - MUCH larger.

[Renton Maclachlan]

Originally Posted by Edward Troxel

DV is NOT uncompressed. DV will get you about 13Gig / hour. Uncompressed will be closer to 60-65Gig / hour - MUCH larger.

hmmm...that rules that out...thanks