[PD] What is an a/d/a sync error?

[thewade]

Sometimes I get a/d/a sync errors (viewable when I press
the DIO errors button); what are these specifically?

For example are they breaks in the sync between jack and
pd, or between jack and the hardware?

Pd version 0.38 TEST10
jackd running in realtime
pd and jack running as root (until Ingo M releases a
realtime kernel patch that runs on x86_64)

Thanks!
-thewade