Comments

Chienworks wrote on 4/9/2008, 2:59 PM
If you're using DV or other similar codecs then the chroma-keyer will be effectively limited by the sampling resolution of the codec. DV uses 2x2 pixel blocks of color (vast oversimplification, but it's enough to understand the following ...) so the chroma-keyer can't exactly mask pixel by pixel. This can lead to rough "stairstep" edges in the image.

.GIF won't have this limitation. It will mask at a full pixel resolution of the image.

Of course, a .gif image won't help you mask by background colors in the video. I'm guessing though that you're asking this question because you want to overlay an image on top of the video and see the video through transparent areas of the image. In this case you'd be chroma-keying the overlaid image and not the video so the problem of DV color blocking wouldn't apply.

So if it's a question of using a transparent .gif or chroma-keying the .gif, it's probably better to have a transparent .gif to begin with. There's no guarantee that the color you want to remove in a non-transparent image doesn't occur in the part you want to keep, unless the image was specifically created with a unique background color. In that case it really makes no difference which way you do it.
Rory Cooper wrote on 4/14/2008, 9:48 PM
I was e-mailed an article saying gif is being fazed out something to do with copyright so all new flash based software do not include them anymore

But as regards the stepping edges I have noticed some graphic editors produce good pngs strait alpha but crappy tiffs pre-multiplied so you also need to check your editor and compare them and go with what’s best

Vegas seems to handle both very well but if the alpha channel is pre –multiplied then you have to key out the back and that affects your alpha channel so
Strait alpha channels work best for me

Particleillusion and some 3d software allow you to render the alpha channel black back removed so how do you get the full benefit in Vegas is there a way
To import just the alpha channel into vegas
Chienworks wrote on 4/14/2008, 10:20 PM
Actually it was a patent on the .gif format, which expired a couple of years ago. Expect to see the support for .gif files coming back into more and more software now.
Rory Cooper wrote on 4/14/2008, 11:01 PM
hi Chienworks

do you know to import alpha channel clips into Vegas ?

do you import as normal and simply add alpha mask or luminance mask which doesn’t work what am I missing?

thanks