There are a few things:
- Get rid of all
<key-device>
lines. I don’t know, if they mess things up, but they are only used forexternal_separate_device
mode and so they can be deleted. - I asume, that channel (device) 2 is the playout channel, but what is device 4 used for? Usually you do not add a channel to the config, when you want to use it for recording.
- Please check if you have set the decklink settings correctly for the fill/key configuration.
EDIT: @Andrea and I posted at the same time, so some stuff is double.