I had a video in a presentation. When I attempted to play it in dual-head mode (the external display of my laptop connected to the projector), the video is played twice -- once on the external display, and once in a part of my laptop's screen. This is fine. The problem is that the audio is also played twice, about a second or so out of sync. So it's like a horrible echo. (This is the first time I've seen pulseaudio actually doing its job, rather than just causing breakage for audio apps. And it's doing precisely the wrong thing.)
Not impressed then that it plays anything in the first place :-) So you've got external monitor plugged in, and mirror monitors turned on with the same stuff getting displayed on both ? or did you get the "speaker notes" screen presenter on your laptop with presentation on projector with the video playing in both ?
Not mirrored; the external screen is 'right of' the laptop's own display. So on the laptop I see the speaker notes -- which is _really_ nice apart from the duplicated audio.
I imagine no-one considered the scenario before and we need to turn off audio for speaker notes embedded video somehow :-)
Need to silence presenter-screen audio
Fix checked in, will be in >= 3.1.0-10.2
sounds right in 3.1.0-10.2