Alpha

1) to enable alpha channels for an image or movie, you need to set the fade to a value less than 1 so:

fade="0 0.999"

<!-- nebula movie -->
<slide>
<duration>25.0</duration>
<background></background>
<title></title>
<layer>
<model coordinate_frame="slide" scale="250" position="0.5 0.5 0" fade="0 0  1 1" rotate="60 1 0 0">starfield2.osg</model>
<stereo_pair fade="0 0.999" position="0.5 0.5 0" rotate="0.01 1 0 0"  scale="1">
<image_left   region="0.0 0.0 0.5 1.0" >stereoMovies/nebulaLA0.5.mov</image_left>
<image_right          region="0.5 0.0 1.0 1.0" >stereoMovies/nebulaLA0.5.mov</image_right>
</stereo_pair>
</layer>
</slide>

.

2) a recent issue with some movies with alpha channels has been solved by introducing a small rotate to the movie :

rotate="0.01 1 0 0"

but it only works, with the rotation in the x as above, see above example also.