audio delay is already in xbmc. it just isn't assigned to any particular buttons.
you can change this by editing keymap.xml and assigning whatever buttons you want to handle it. note that each button can only be assigned to a single action, though, so you might have to miss out on some other action. (although, the left and right triggers are currently not doing anything when viewing movies, so they could be used).
the action id's for audio delay are defined in key.h as:
#define action_audio_delay_min 54
#define action_audio_delay_plus 55
thus, to map audio delay minus to the left trigger, you'd add:
Quote:<action>
<description>decrease audio delay</description>
<id>54</id>
<gamepad>lefttrigger</gamepad>
</action>
this needs to be added in the <window> </window> section for the fullscreen video.
enjoy.
oh, and subtitle delay is already there as well.