Delay API for live devices
Would you consider adding a function to get the delay between the sample currently being played and the sample that was last given to ao_play? Something like snd_pcm_delay or its equivalent for others devices.
Such a function would be very useful in cases where audio synchronization is essential, like video programs, or when trying to play the same sound on several computers. Obviously, its result would only make sense for live devices, but it could just return 0 for non-live devices.