Is it possible to have the whole composition use an alpha channel?
Each rendering layer does indeed have an alpha channel, but when
the whole composition is shown (in QC, QT or whatever) -- the
background is black.
The background is by default ARGB=(0,0,0,0), which looks like black,
but it's actually transparent as the alpha channel has a value of 0.
So in QT, you should be able to composite the QC tracks over the
other tracks.
