According to Antares support, here is what you can do to determine whether to use the Host or Internal clock settings in the grpahical mode of Auto-Tune5.

For hosts that do not provide valid time
information, Auto-Tune 5's clock display and
selection functions let you use an internal time
reference for Auto-Tune 4 style operation.

To determine if your host supplies valid clock
information, click the Host button to select
the host-supplied clock and put your host into
Play. If Auto-Tune 5 is receiving valid timing
information from your host, the Position
display should constantly update to reflect your
current position in the track. Moving forward
or backward in the track should result in
corresponding display updates. If this is in fact
happening, you have confirmed your host's
timing info. Simply leave the clock setting
on Host for Tracking and Correcting pitch.

On the other hand, if the display does not
update or if it does not accurately reflect your
host's transport, Auto-Tune 5 may be getting
bad (or no) clock information. In that case, you
will need to use the Internal clock option.

To select Auto-Tune 5's Internal clock, click the
button labeled 'Internal'.
To track and correct pitch in Internal Clock mode:
1. Use your host transport to move to the
beginning of the section you want to correct
and note that position, as you will need to
return to that precise place for correction.
2. Click the Reset button to set the clock
position to 00:00:0.
3. Click the Track Pitch button, play the desired
audio and then stop the transport.
4. Use the various tools described below to
create your pitch correction curves.
5. Use your host transport to return to the
precise start location defined in step 1.
6. Click the Reset button to reset the clock
position to 00:00:0.
7. Play your audio. Auto-Tune 5 will apply your
corrections.