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MillimeterOptimizing Encoding Performance with Apple Final Cut Pro, Part 2
Nov 3, 2009 12:00 PM, By Jan Ozer
Meet Apple Qmaster.
Figure 1. System preferences. Qmaster is on the bottom in the Other category.
Apple originally created Qmaster to enable Compressor and other rendering-intensive applications to use other Macs on a network cluster to share encoding tasks. That was back in the bad old days, when computers typically had single or dual processors and encoded very slowly. In this multiple-computer role, Qmaster could be challenging to set up, fine-tune, and maintain, because it involved separate computers on a LAN and sending huge files over that network to distribute the encoding.
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If you have a multiple-processor computer, you can also use Qmaster to help spread the encoding load over those multiple processors, which can dramatically boost encoding performance. In this role, Qmaster is much easier to set up and maintain than in its multiple-computer role. If you have a two-, four-, or eight-core computer and frequently render multiple files with Compressor, you really need to try Qmaster. In this article, I'll walk you through setting up and using this program.
Setting up Qmaster
To set up and start Qmaster, open your Mac's System Preferences window. On the bottom, in the Other category, click Apple Qmaster (Figure 1).
The Apple Qmaster configuration window opens. If Qmaster is running, click Stop Sharing on the lower right to stop the sharing so you can configure the program. On the top, choose the "QuickCluster with services" radio button. Note that this is critical, as neither of the other options will allow you to access the cluster from within Compressor. You know you've made a mistake if the "Identify this QuickCluster as:" text-entry box remains grayed.
Figure 2. The basic Qmaster options.
In the Services window, choose both Shared and Managed checkboxes for the applications you want to distribute over the multiple cores on your computer. I've selected Compressor only because I don't use Shake. Then click Options for the selected service button.
This is where you choose the number of instances available for Qmaster. There are two factors to consider: the number of actual cores on your computer and the amount of RAM. By default, Qmaster will select one instance for each processor on your computer. I've read some articles that recommend using one instance for each two cores on your computer, which will leave plenty of cores around for editing or checking email. Another recommended choosing one fewer instance than you have cores on your computer, or seven instances on an eight-core computer.
Figure 3. Choose how many cores to use during rendering with Compressor.
I would choose the default value and modify this, if necessary, based upon your experience. If you want to continue editing while rendering and the system becomes unresponsive, lower the number of cores. If you're rendering over a weekend, jack the number of cores to the max and go home.
For RAM, here's a tech note from Apple: "Be sure your computer has an adequate amount of RAM before configuring it to support running multiple services. A minimum of 1GB of RAM per service is recommended."
So, if you've got 4GB of RAM on an eight-core system, don't go higher than four instances. Or buy more RAM—you'll be glad that you did.
Continue the discussion on “Crosstalk” the Millimeter Forum.