virtualbox.org

I recently reinstalled a machine to downgrade it from ubuntu 13.04 to 12.04. I have virtualbox guest machines which played video fine (via vlc) when the host ran 13.04, but play it extremely choppily now that it's running 12.04. The same video plays fine when run directly on the host. This happens with ubuntu/debian virtualbox, and oracle virtualbox 4.1 and 4.2. The guests run ubuntu 12.04 or 13.04, and all have 3d video acceleration turned on, and the maximum video memory.

Is there a less drastic fix for this than upgrading the host back to 13.04?

you could try opening the vlc preferences and changing the video output to x11. might help.

Is it Ubuntu with Unity Desktop?

If yes: If you move Windows on the desktop,is it choppy too?

Unfortunately this problem simply went away with no apparent reason. Thanks for the suggestions.

check out the fat bloke: https://blogs.oracle.com/fatbloke/entry ... ntu_guests
It may help.