Specifications

Chapter 6: DigiRack Real-Time TDM and RTAS Plug-ins 91
the polarity (phase) of one of them, the signals
will be of opposite polarity and cancel each
other out. This technique is convenient for find-
ing the exact delay setting for any plug-in.
To determine the delay of a plug-in by inverting its
signal phase:
1 Place duplicate audio regions on two different
audio tracks and pan them to the center (mono).
2 Apply the plug-in whose delay you want to
calculate to the first track, and a Time Adjuster
plug-in to the second track.
3 With TimeAdjuster, invert the phase.
4 Control-drag (Windows) or Command-drag
(Mac) to fine-tune delay in one sample incre-
ments, or use the up/down arrow keys to change
the delay one sample at a time until the audio
signal disappears.
5 Change the polarity back to normal.
6 Save the TimeAdjuster setting for later use.
Comb-Filter Effect Cancellation
Adjust the delay with the signal in phase until
any comb-filter effects cancel out.
Viewing Channel Delay
Because plug-ins display their delay values in
the channel delay indicators, this can be used as
another method for determining delay compen-
sation.
To view time delay values and use TimeAdjuster to
compensate for the delay:
1 Control-click (Windows) or Command-click
(Mac) the Track Level Indicator to toggle be-
tween level (that appears on the display as
“vol”), headroom (“pk”), and channel delay
(“dly”) indications. Delay values are shown in
samples.
2 Apply the TimeAdjuster plug-in to the track
whose delay you want to increase, and Control-
click (Windows) or Command-click (Mac) its
Track Level indicator until the channel delay
value is displayed for that track.
3 Change the delay time in TimeAdjuster by
moving the Delay slider or entering a value in
the Delay field, until the channel delay value
matches that of the first track.
4 Test the delay values by duplicating an audio
track and reversing its phase while compensat-
ing for delay.
When to Compensate for Delays
If you want to compensate for delays across your
entire system with Time Adjuster, you will want
to calculate the maximum delay incurred on
any channel, and apply the delays necessary to
each channel to match this channel.
However, this may not always be necessary. You
may only really need to compensate for delays
between tracks where phase coherency must be
maintained (as with instruments recorded with
multiple microphones or stereo pairs). If you are
working with mono signals, and the accumu-
lated delays are small (just a few samples, for ex-
ample), you probably needn’t worry about delay
compensation.
Determining the DSP delay of track inserts (Mix window
shown)
For more information about delays and
mixing with Pro Tools HD, see the
Pro Tools Reference Guide.