Using Distributed Audio Processing

Distributed audio processing allows you to expand the processing capacity of your Logic Pro system. It does this by offloading calculations for software instruments or effects to additional Mac Node computers, connected via Gigabit Ethernet. This is perfect when using numerous instances of processor-intensive software synthesizers or effects, such as Sculpture or Space Designer.

Additional Mac computers do not require further copies of Logic Pro, nor any MIDI or audio hardware.

You can find the Logic Pro Node Installer on the Logic Pro Installation DVD. Install it, and set the system volume of your Node machine as the destination. The Logic Pro Node application has no parameters or GUI elements. It simply needs to be open on the Node machine before you start Logic Pro.

Tip: If you plan to use a Mac solely as a Node machine, you may want to place the Logic Pro Node application in the Startup Items folder. You may also consider using Apple Remote Desktop to control additional Mac computers from your primary system. In this scenario, your Node machines don’t need their own monitors or keyboards.

Considerations for Distributed Audio Processing

Distributed audio processing actually uses the built-in networking capabilities of Mac OS X. You will need to set up an Ethernet network connection between all computers, via the Network pane of the System Preferences. See Mac Help for details on setting up a network.

Networking Considerations

The primary (host) computer will be a Macintosh computer with an Intel core processor, equipped with a Gigabit Ethernet port. Ideally, node machines need one or more Intel processors (a Gigabit Ethernet port is standard on all Intel Mac computers).

If you want to run multiple nodes, a Gigabit Ethernet switch is required.

It is recommended that you only use the network for distributed audio processing when Nodes are active—other activities will affect performance.

Note: You must disable the software firewall. If you want to access the Internet via your network, use of a router with a hardware firewall (or separate computer with a firewall), is recommended.

Plug-in Considerations

Some Audio Units effects may not support the Node functionality of Logic Pro. You can disable the Node processing for incompatible Audio Units effects in the AU Manager application.

A number of Node-compatible third-party Audio Units effect plug-ins may open a dialog on the Node machine. You will not see this dialog on the host machine (unless Remote Desktop is in use). The Open dialog will lead to timing errors, and the connection to the Node will be disrupted.

Important: You can only process a plug-in on Node machines when all Nodes have an identical version of this plug-in installed.

Enabling Distributed Audio Processing

The following assumes that you have correctly installed the Logic Pro Node application (and have an identical plug-in set) on all Node machines, and that it is open.

To set up, and activate, nodes in Logic Pro
  1. Open the Nodes preferences by doing one of the following:

    • Choose Preferences > Audio (or use the Open Audio Preferences key command), then click the Nodes tab.

    • Click the Preferences button in the Arrange toolbar, choose Audio from the pop-up menu, then click the Nodes tab.

    Figure. Audio Node preferences.
  2. Select the Enable Logic Nodes checkbox, and select computers in the list below:

    • Selected (active) Nodes are used by the host (Logic Pro system).

    • Dimmed (inactive) Nodes are due to one of the following:

      • The machine is not connected to the network.

      • The machine does not have the Logic Pro Node application running.

      • The machine is in use by other hosts. They can remain checked for future use (when Logic Pro is next opened).

    • Unselected Nodes are not used by the host—they are, however, available to other hosts.

    • The list retains a history of previously connected Nodes. You can remove Nodes by clicking the Remove button. This is useful if you’ve renamed a Node machine, or if you’re sure that a Node machine will never be used again.

  3. In the Arrange area, configure the track header to display the Track Node buttons:

    1. Open the Track Configuration window by choosing View > Configure Track Header (or use the corresponding key command). You can also Control-click (or right-click) any track header in the track list.

    2. Select the Track Node button’s checkbox.

    The Track Node buttons have four possible status indicators:

    Figure. Arrange track header area showing the four status indicators of Track Node buttons.
    • Disabled: The track is calculated on the local host (in Logic Pro, as per usual).
    • Enabled and inactive: This track can potentially be calculated on the Node.
    • Enabled and active (glowing): The track is actually being calculated on the Node.
    • Sync pending: Data synchronization between the host and Node has not yet been established (if the Node is not running, for example).
  4. Click a Track Node button in the track list to offload that track’s processing duties to a Node.

    Tip: You can use track button slide activation to enable distributed audio processing on multiple tracks. See Using Track Button Slide Activation.

  5. Click an active Track Node button to disable distributed audio processing for the track.

Important Information on Using Nodes

Logic Pro automatically determines if enabled tracks are actually calculated on a Node (and which Node, if multiple Node machines are available), or on the host computer. This depends on system resources and network traffic.

The distribution of tasks to Nodes is based on an estimate of the processing resources a certain stream will cost the host system. While the processing load of audio effects is relatively constant, the performance of software instruments may vary greatly, depending on the chosen setting, and on the number of simultaneously played voices.

Compensation of latencies caused by the network and processing occurs on playback tracks—audio or software instrument, resulting in perfect timing—but this is obviously not possible for live performance tracks.

What Can’t Be Processed on a Node

The Node buttons are available for all audio and software instrument tracks. There are, however, some exceptions:

  • EXS instruments: These are always calculated on the host. The reason for this is the potentially demanding transfer of samples via the network, resulting in a slowdown of audio processing over the network. The sample library needs to be present on the host computer itself.
  • Multi-output instruments such as Ultrabeat: Further to this, Ultrabeat also has a similar problem to the EXS24 with sample-based kits.
  • Audio Units software instruments: When an Audio Units software instrument track is selected, the Node button is automatically turned off.

The Logic Pro Node application can process Audio Units effects.

It is possible, however, that some Audio Units effects may not support the Node functionality of Logic Pro. You can disable the Node processing for incompatible Audio Units effects in the Audio Units Manager.

Figure. Audio Units Manager window.

It is not possible to calculate input, output, bus, or aux channels on a Node.