Splitting video for a video wall with 2 graphics cards

[fortuneguy]

I hope somebody can help. I'm working on a 4x3 video wall using 2 matrox graphics cards that power 6 monitors each (2 sets of 2x3 monitors side by side). Each set of 6 has been configured as a single "desktop", so windows effectively thinks it has 2 monitors (A and B).

A1 A2 B1 B2
A3 A4 B3 B4
A5 A6 B5 B6

I've written a custom video player using libvlc but I'm having some performance issues when playing video across monitors from both video cards (video playback is slow and jerky). It seems that hardware acceleration is only available if the video is played within a monitor set belonging to a single graphics card. I can play 2 videos side by side at full speed as long as they remain within their monitor "space".

To get around this I'm considering using 2 players: the first to play the left side of the video on the left bank and the second to play the right half of the video on the 2nd bank. Is it possible to configure VLC to split a video in this way so that both halves get accelerated properly? If not I'd have to find a way to sync 2 players perfectly.

[Rémi Denis-Courmont]

If you provide custom video output callbacks, the callbacks are responsible for acceleration (if any). LibVLC hardware acceleration can intrinsically not be used with custom callbacks - regardless of what the ultimate destination is. So the question does not make much sense.