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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 4. Advanced Qmaster options.
After you've chosen the number of cores to use, name your QuickCluster and deselect the "Include unmanaged services from other computers" checkbox unless you intend to create a multiple-computer cluster or access a cluster from another computer. If you don't deselect this and you have other computers running Qmaster on the network, their clusters will show up in Compressor, which could get confusing.
For example, on my network (right now), I have four Macs, all running Qmaster, though I don't share encoding between them. If the "Include unmanaged services from other computers" is enabled, when I try to choose a Cluster in Compressor, the clusters from these other computers appear. This is confusing, and if I choose the wrong cluster, Qmaster might try to spread the encoding over multiple computers, which isn't my intention. So, deselect this checkbox unless you intend to share encoding over multiple computers.
Figure 5. Make sure you assign the encoding task to the new cluster, not This Computer.
On top of the Qmaster configuration window, click the "Advanced" button to open those options. If you're not running Qmaster over multiple computers, deselect "Allow discovery via Bonjour." If desired, click the "Show Apple Qmaster service status in the menu bar" checkbox so you can see when Qmaster is working. You can leave the other options at their defaults and click Start Sharing to get the party started.
Figure 6. Your new cluster will get its own category in Batch Monitor.
Once Qmaster is running, you access it from Compressor—once you click Submit the first time to kick off encoding. Before clicking Submit again, make sure you select the cluster that you created rather than "This Computer."
If you're used to checking your work in Batch Monitor, you'll note that the Cluster gets its own category on the left hand side. Click that and the encoding jobs that you've submitted appear.
Figure 7. CPU use in the 96-percent range via Qmaster.
When you check Activity Monitor, for most encoding tasks, you'll see significantly higher CPU use. Though the red Compressor/ TranscoderX with (Not Responding) looks scary, it's probably appearing because the process is too busy to respond, not because it's about to crash. Here I'm encoding multiple files to H.264, and you can see in Figure 7 that the system is using all but 3.32 percent of available CPU, up from about 30 percent when encoding without Qmaster.
Table 1. Performance with and without Qmaster on a 2.93GHz, eight-core Mac.
How much will this extra CPU use reduce your encoding times? This depends upon the codec. Apple's H.264 codec uses multiple cores without Qmaster, though Qmaster makes it much more efficient for both single and multiple file encodes, as you can see in Table 1.
With other codecs, such as On2 Technologies' relentlessly single-threaded VP6 codec, accessed via Flix Exporter, Qmaster can't apply more than one CPU core to the task, so it doesn't affect single-file encoding times. As you can see in Table 1, however, if you're encoding more than one file, the time savings can be significant.
Qmaster and Final Cut Pro 7
If you've tried sending an encoding job from Final Cut Pro 7 to Compressor via the new Share option, you probably noticed that Qmaster crashes the encoding operation in Compressor. I asked Apple about this when reviewing Final Cut Pro 7, and the Apple reps explained that on a single computer, Qmaster works by opening up multiple instances of the encoding program and assigning cores to each instance.
However, Final Cut Pro—which actually performs a portion of the encoding when you choose the Share command—doesn't support multiple instances on the same computer, and if you attempt to load multiple instances, it crashes the encoding. For this reason, you can't use Qmaster with the Share option on a single computer, though you can with a multiple-computer cluster. You can still access Qmaster on a Final Cut Pro 7 enabled system by rendering to a QuickTime reference movie, loading that file into Compressor, and then following the procedure outlined above.
Continue the discussion on “Crosstalk” the Millimeter Forum.