Starting the Engines

   By Lisa F   Categories: Audio SoftwareGeneral

As with any complex piece of machinery, there are various settings that you may need to adjust each time you want to use it. This is certainly the case with Pro Tools. I recommend that you always check the Playback Engine settings and the I/O Setup at the start of any new session. You may also need to make some changes to the Hardware Setup if you want to hook up additional hardware.

Avid Audio Engine

If you are using Avid hardware, Pro Tools 11 will use the Avid Audio Engine. This Audio Engine is a real-time operating system for digital audio recording, playback, and processing designed for use with Pro Tools and Avid audio hardware that is automatically installed on your system when you install Pro Tools. If you are using hardware made by another manufacturer, Pro Tools 11 will use Core Audio on the Mac or Audio Stream Input/Output (ASIO) on Windows.

Apple’s Core Audio provides the audio connections between software applications, such as Pro Tools 11, Digital Performer, Cubase, Nuendo or Logic, and any audio hardware installed on a computer that uses Mac OS X.

Similarly, Steinberg’s ASIO provides the audio connections between software applications such as Pro Tools 11, Digital Performer, Cubase or Nuendo, and audio hardware installed on a computer that uses Windows.


Pro Tools software can only record up to 32 input channels of audio or play back up to 32 output channels of audio, when using audio interfaces with the Avid Audio Engine, or supported Core Audio (Mac), or ASIO (Windows) drivers. So if you need more channels for I/O (Input and Output), you will have to use Pro Tools HD software with Avid HDX or Native hardware.

Avid Video Engine

Avid’s Video Engine works with QuickTime video, so you can use any video that you have available in this format. The Video Engine also works with a wide range of Avid HD and SD MXF video formats on Pro Tools video tracks without the need for transcoding these first, including Avid DNxHD. It also lets you monitor Avid HD and SD MXF, and QuickTime media using Avid Nitris DX, Mojo DX, and other Avid qualified third-party video interfaces.


If you want to use video in your Pro Tools session, then you will need to tick the box in the Playback Engine dialog to enable the Video Engine – otherwise, the video track(s) in Pro Tools will not work.

The Playback Engine Dialog

In the Playback Engine dialog, Pro Tools provides a pop-up selector that allows you to choose the audio ‘Playback Engine’ for use with your audio interfaces. The available options will depend on which audio interfaces are connected and have compatible drivers installed.

Changing the Playback Engine can be useful if you have two or more audio interfaces connected to your computer with different routing configurations in your studio or if you want to prepare a session for use with a specific interface on a different system (e.g. you might want to prepare a session created on your Avid HDX system for use with the built-in audio on your Mac laptop).

On the Mac, for example, there will always be a ‘Built-in’ audio interface, and there may be another if you are using an Apple display monitor that has audio input and output capabilities. On Mac systems, you can also select the Pro Tools Aggregate I/O option, which lets you use a combination of built-in inputs and outputs at the same time – see Figure 2.1.

Figure 2.1: Choosing Pro Tools Aggregate I/O in the Playback Engine on the Mac.

You can confi gure the I/O options for Pro Tools Aggregate I/O using the Audio Devices window from the Mac’s Audio MIDI Setup utility software – choosing an appropriate combination of inputs and outputs – see Figure 2.2. These inputs and outputs will become available in the I/O Setup dialog if you open this and click on the Default buttons in the Insert, Input, and Output tabs.

Figure 2.2: Configuring Pro Tools Aggregate I/O in the Audio Devices window.

The H/W (Hardware) Buff er Size pop-up selector in the Playback Engine dialog – see Figure 2.3 – lets you choose the size of the buffer used to handle host-processing tasks such as processing with host-based, or ‘‘Native” plug-ins.

Figure 2.3: Hardware Buffer Size and Host Engine settings.


You can open the Audio MIDI Setup utility by choosing the MIDI Studio sub-menu item available from the MIDI menu item in the Setup menu in Pro Tools. This opens the MIDI window by default, but then you can open the Audio window from the Window menu in the Setup utility.

On all Pro Tools systems, lower settings reduce MIDI-to-audio latency – for example, the delay between playing notes on your MIDI keyboard and hearing the audio response from a virtual instrument. Lower settings can also improve screen response and the accuracy of plug-in and mute automation data.

If you are using lots of ‘Native’ plug-ins, you should choose a higher buff er size to allow for the greater amounts of audio processing required.

The Host Engine settings provide options for error suppression during playback and recording and the option to use dynamic plug-in processing.

There may be times when it makes sense to tick the box to Ignore Errors During Playback/Record. For example, when you are working with several instrument plug-ins and these are stretching the capabilities of your computer’s CPU to the point where you are hearing clicks and pops in the audio. In this case, you may choose to work with reduced audio quality, accepting that there are clicks and pops in the audio while you are trying out arrangement ideas. Later, when you want to make sure that you are getting the highest possible audio quality, you can disable this option.

Ignoring errors requires at least 128 samples of additional buffering on some systems. Host-based Pro Tools systems have an option to Minimize Additional I/O Latency. Enabling this option restricts any additional latency due to ignoring errors during playback and recording to 128 samples. With this option disabled, the buff er used for error suppression will be at least 128 samples or half the H/W Buff er Size – whichever is greater.

The Dynamic Plug-In Processing option maximizes plug-in counts by dynamically reallocating host-based processing resources as needed, so plugins only use CPU cycles when they are actually processing audio. Normally, you will want to make sure that this option is enabled.


On host-based Pro Tools systems, lower settings reduce all input-to output monitoring latency on any record-armed tracks or Auxiliary Input tracks with ‘live’ inputs. On Avid HDX systems, lower settings reduce the monitoring latency that occurs on tracks that have one or more Native plug-ins. Lower settings can also improve the accuracy of MIDI track timing on systems without a MIDI interface that supports time stamping and on tracks using MIDI virtual instruments that do not support time stamping. 


If you are using a slower computer, you may want to disable the Minimize Additional I/O Latency option to avoid adverse performance.


The Minimize Additional I/O Latency option is only available if the Ignore Errors During Playback/Record option is enabled and the Pro Tools system you are using requires additional buff ering for error suppression, as is the case with the following: Mbox Pro and Mbox 2 Pro on Windows and the Mbox family devices, Digi 002 and 003 devices, Eleven Rack, and Pro Tools Aggregate I/O on the Mac.

Excerpt from Pro Tools 11: Music Production, Recording, Editing, and Mixing by Mike Collins © 2013 Taylor & Francis Group. All Rights Reserved.


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