I just submitted a patch which enables setting global AV delay. Some displays have complex video processing and can introduce a noticeable delay in video. This functionality can be used to compensate for this within XBMC. The patch enables specifying different delays based on display refresh rate. It can also be used for working around the infamous 24p 250 msec audio delay bug (or whatever it is ).
Global delay is set in advancedsettings.xml. A sample describing supported options is here:
<!-- Compensate display latency (video lag). Latency is given in msecs. -->
<!-- Global default display latency -->
Override latency for given display (not video) refresh rates.
When XBMC is in windowed mode, override is ignored. Multiple
overrides are allowed.
Syntax of an override entry:
<min>, <max> refresh rate range, OR
<rate> exact refresh rate
<delay> display latency for the given refresh rate
<!-- Example: display has 125 msec latency at 23-24 Hz -->
<!-- Example: display has 50 msec latency at 50 (+/-0.01) Hz -->