Can I watch a film on an iPad but only extract the audio to e.g. surround headphones? Or does the picture also have to go through this device to a monitor, Tv?
I just tried again and found out that it depends on the app used. It works for me with the official YouTube app from Google (there is a kind of mirroring -> image is displayed on the iPad around the beamer), but not with Infuse, for example.
The unit taps the sound signal from an HDMI cable. If your iPad has an HDMI output, then you can tap the sound with it. The iPad can probably display the picture itself at the same time, so it doesn't matter if you use the picture part on HDMI.