[PD] transparent video or: how to concatenate strings?

[chris clepper]

On Jul 20, 2004, at 9:51 AM, andreithomaz wrote:

> hello list,
>
> I am using GEM on WindowsXP. I would like to mix videos with 
> transparency (that is, with alpha channel). But I cann't find a codec 
> that supports that. Do you know anyone?

You are right that video has no alpha channel so finding a video codec 
that supports one is nearly impossible exactly for that reason.  I 
would suggest looking into computer graphics codecs like Apple/Adobe 
Animation included with Quicktime.  It will include alpha when the 
color depth is set to 'Millions of Colors+'.

> A way to solve the problem would be to show a image sequence (PNG 
> files with 32 bit color). But, for that, I would have to transform a 
> number into a string, and concatenate it with a string (for exemple, 
> "frame" + number + ".png"). Is it possible to make that?

There are utilities to put image sequences into .mov or .avi containers 
- I use Quicktime Pro to load the image sequence GEM writes to disk and 
make it into a single .mov file.  This would be a lot easier than what 
you propose.

cgc

> thanks a lot,
> andrei