You need to export with an alpha channel. The lossless Lagarith codec allows you to do that...
However, at some point you need to use After Effects to key an image where the green screen was - that's kind of the point of green screen.
Can I ask how you want to use transparency if it's not to re-key a backcround?
Thanks a lot for your quick reply.
The video is a talking presenter. We did not want to put him onto any background, but wanted his background just to be transparent. This way, we can embed the FLV video to PowerPoint, and put whatever background, text, and animation onto that PPT slide.
Meanwhile, I'll try exporting with Alpha channel as you suggested. But I don't see "Alpha" is an option when I want to export as FLV?
> I'm a new user of After Effect CS4. I searched the forum for the answer to my question, but couldn't find it. Maybe my question is too basic. <
We see questionsa about how to render with transparency daily. Search again, try harder.
Open the manual. There is an entire section about how to export and how to select appropriate codecs. You're looking for codecs that are particualrly designed to carry the alpha. There are only a few. And you alos need to understand the difference between straight and premultiplied alpha although it's easier to just use straight.
Thank you both for your quick response and great help! I searched more a bit further and found this tutorial, which helped me to export correctly.
That link points to a section of a really good book called "After Effects For Flash: Flash For After Effects" by Richard Harrington and Marcus Geduld.
I bought it awhile back and it helped me quite a bit, not just for Flash>AE and AE>Flash issues, but for the entire Production Premium suite (CS4).
So many books are just recipes that show how the authors created a particular effect or composition. This one actually explains why they chose the settings they did and does it in the context of learning the fundamentals of motion graphics, whether you're using vector animation, HD video or combining both in the same project.
It comes with a DVD that has all the exercise files and some video tutorials.
I guess at this point you might think I'm related to one of the authors! I'm not, I'm just a satisfied owner of what I consider an essential book for beginners.