There appears to be a minor performance benefit to not waking up the
delivery thread (if used) immediately upon enqueueing the first sample,
but rather to wait (typically) until the end of the packet. In a
latency measurement it probably makes little difference: one shouldn't
use asynchronous delivery if one needs the lowest possible latency, and
the end of the packet is reached rather quickly normally.
Signed-off-by: Erik Boasson <eb@ilities.com>