Alpha Channel

wolfbass wrote on 8/14/2005, 5:15 AM
Hi Guys! On a deadline.

I've got a DV AVI of Still rendered and back on the time line. I've used pan crop so all of each still is within the safe distance. It's a combonation of Portrait and Landscape stills.

I want to have a background show through where the black is.

How would I do this?

Any help appreciated.

P.S. RTFM doesn't help, I've looked there. Clear as Mud!

Cheers,

Andy

Comments

winrockpost wrote on 8/14/2005, 6:11 AM
I'm pretty sure If you have rendered the pics to DV avi, the black is really black, not transparent.
beerandchips wrote on 8/14/2005, 6:27 AM
I'm pretty sure If you have rendered the pics to DV avi, the black is really black, not transparent.


This is correct. DV is 24 bit. So, there is no alpha channel in it. Since you have alreay rendered to avi you can cut a mask to achieve what you want.

sn
wolfbass wrote on 8/14/2005, 6:48 AM
Thanks for the replys guys.

The pix are a mix of Portrait and Lanscape, so the mask thing isn't going to work.

What would I render to if i wanted an alpha channel?

I don't mind going back a few steps, it's only 8 mins or so.

Andy
Chienworks wrote on 8/14/2005, 6:53 AM
Uncompressed AVI will allow 32 bits with alpha channel. Be prepared for huge files. 8 minutes will be 15GB or so.

Have you considered using Chroma Key to let the background show through the black areas?
JohnnyRoy wrote on 8/14/2005, 7:22 AM
> I don't mind going back a few steps, it's only 8 mins or so.

Then why don’t you go back and add another track below the current track so that it creates the background in the first place? This is the easiest way to fix this if you have the original project.

~jr
wolfbass wrote on 8/14/2005, 7:55 AM
Because the black borders of the photos dont allow the background to show through, as it's not transparent.
JohnnyRoy wrote on 8/14/2005, 4:59 PM
How did the nontransparent black borders get there? Cuz’ when I have portrait stills on the timeline, the black border is transparent and I always fill it with a background of my choice.

~jr
murk wrote on 8/16/2005, 3:17 PM
In regards to rendering with Alpha channel, I recommend rendering as Quicktime Animation Codec in Millions of Colors+ and 100% quality. This is better compression than Huffyuv and is friendly to both Mac & PC platforms and it is lossless.

There is also a PNG format for Quicktime which is also lossless and compresses a little better than Animation. The PNG codec takes a little more CPU however.