Maximum number of movie or videoplanes...

Hi there,
I have a video patch in which there is a certain number of movie_reader, an object of mine made of a jit.qt.movie (with the uyvy gl transfer...), some jit.gl.slab and a jit.gl.videoplane.

I followed the prescriptions from Vade to optimize movie playing, everything was working fine, thanks to him. When I use 5 movie readers, my fps is at 60, which is the best I can get.

But if I use more than 5 movie_reader(8 for example), which means 8 jit.qt.movie and 8 jit.gl.videoplane, my fps drops to 30. 6, 7 or 8 movie_reader give the same result in term of fps...

I use multiple videoplanes, because it seems to be the best way (with color 0. 0. 0. $1) to do some simple compositing with many movies.

Anybody has a clue to explain the frame drop??? So, is there a maximum of jit.gl.videoplane?

Or would there be a better way to composite (add) up to 8 movies?

Thanks a lot.

Ps. I can't post the patch here, because it is a very complex patch, in which commands are sent by a text editor, with many files attached to it. I hope, some of you will be able to help me without seeing all the patch cords...