Transparent background in AVI file?

organism_seven wrote on 4/2/2003, 6:08 PM
Hi,

I have produced a small animated logo for overlaying on top of video footage.
I have used a 3D authoring package which allowed me to output the animation
as 32bit TGA files which maintains the alpha channel. (200 single images)
When I import these into Vegas as an image sequence the background is transparent.
Thats great, but because the timeline is trying to work its way across 200 still images, the playback is jerky.
Once I had these images in the timeline, I exported them as a single AVI file.
Placing this AVI file on the timeline allows a silky smooth playback.
But I have lost the transparency channel. The background is pure black.
Is it possible to produce an AVI file that maintains the alpha channel that is embedded in the original still images?
If so, can anyone explain to me how to do this?
Thanks.

Regards.
organism seven

Comments

Tyler.Durden wrote on 4/2/2003, 7:18 PM
Hi O7,

You might try to save as an uncompressed avi or QT, the alpha option should be available there.

The playback of uncompressed can load the processor and disk, so high framrate may still need prerendering or ram rendering.



HTH, MPH

Tips:
http://www.martyhedler.com/homepage/Vegas_Tutorials.html

vicmilt wrote on 4/2/2003, 7:24 PM
Another workaround would be to put a solid chroma green background layer under the pngs before you render the avi.
Then use the avi where required and chromakey out the background.
VIDEOGRAM wrote on 4/2/2003, 8:28 PM
I do this often.
I produce a 32 bits Quicktime file from my still sequence threw After Effects. This .mov file can then easily be keyed over any video in VV4.

Gilles
organism_seven wrote on 4/3/2003, 11:11 AM
Hi,

Thanks for the help.
I loaded my AVI in QuickTime and was able to convert it to a QuickTime which supports a transparent background.
Works perfectly when imported into Vegas.
Still think its strange though that this could not have been done with AVI files, without creating huge file sizes!

Regards
Organism Seven.
SonyDennis wrote on 4/3/2003, 11:48 AM
Most AVI codecs don't encode the alpha channel; uncompressed does, DV does not.

If you have alpha, preserve it. Adding green in it's place and the using the chromakey filter is not going to look as good.

///d@