Apple Logic Pro X - Manual (Page 505)

Chapter 16 Mix a project 505
Work with plug-in latencies
Audio processed through plug-ins is subject to small timing delays, known as latency. For
example, a software instrument running inside Logic Pro will only have an output latency,
because it’s generated inside the application. An audio recording that is being monitored in real
time will have both an input and an output latency. These two values are summed, resulting in
an overall monitoring latency figure. Each further process—such as the use of an effect plug-in,
for example—will also add an amount of latency, which is combined with the input and output
latency figure, depending on whether a software instrument or audio channel strip is in use.
In Logic Pro, you can compensate for internal latencies introduced by plug-ins, ensuring that all
track and channel strip output is perfectly synchronized.
You can also turn plug-in latency compensation on or off, for audio and software instrument
tracks or for all channels (audio, instrument, aux, output, and ReWire). When this setting is turned
on, Logic Pro compensates for latency introduced by plug-ins, ensuring that audio routed
through them is synchronized with all other audio. This is achieved by calculating the amount
of latency caused by plug-ins, and then delaying audio streams by an appropriate amount—or
shifting instrument and audio tracks forward in time.
Turn on Low Latency mode
Do one of the following:
m Click the Low Latency Mode button in the control bar.
m Select the Low Latency Mode checkbox in General Audio preferences.
Plug-ins will be bypassed to ensure that the maximum delay that can occur across the entire
signal flow (of the current track’s signal path) remains under the Limit slider value in General
Audio preferences.
The sound may change when you turn on Low Latency mode. Depending on the plug-ins in
use, the change in sound can be anything from subtle to dramatic. If plug-ins being used do not
exceed the total latency limit, there will be no audible difference.
Turn on plug-in latency compensation
m Choose an option from the Compensation pop-up menu in General Audio preferences.
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If latency-inducing plug-ins are inserted into audio or instrument channel strips, Logic Pro
automatically shifts these tracks forward in time. The advantage of this method is that other
channel strips (that do not contain latency-inducing plug-ins) do not need to be delayed.
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If latency-inducing plug-ins are inserted into aux or output channel strips (or ReWire channels,
if used), Logic Pro delays all other audio streams by an appropriate amount.
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With plug-in latency compensation set to All, Logic Pro shifts the bass track forward by 10 ms,
thus synchronizing the bass and drum tracks. Logic Pro will then delay both streams routed
to the output channel by 30 ms, aligning them with the guitar tracks. The aux channel strip
that the vocals are streamed to is also delayed by 15 ms, aligning it with the drum and guitar
streams (in other words, the 15 ms delay is increased to 30 ms). The precise calculations
required for each stream are handled automatically.