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George Ramos

Final Cut Pro generated an error or unexpectedly when using compressor with Qmaster Virtual Cluster

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Hello all I have Final Cut Studio 3. I am using the latest Final Cut and the latest compressor.

I have a Core i7 so i am trying to use all 8 virtual threads or at least four. However when I use the "This Computer" option in compressor it is not an issue. It will compress fine. However, when i use the virtual cluster i set up with QMaster i get the dreaded "Final Cut Pro generated an error or unexpectedly" and it fails. I am unsure what to do. Here are the circumstances:


When I to compressor from FCP and use "this computer" it is no problem.

When I send to compressor from FCP and try to use your personalized cluster (taking advantage of those expensive cores!) it won't work. it fails and give me the aforementioned error.


PS I know that I can make the file quick time self contained movie fm final cut and send it to compressor, but this program should work on it own without doing that.


I have enclosed a video which can be seen at:





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Virtual Clustering works by launching multiple copies of the Compressor encoder, each of which needs access to the source media that you are compressing. This is fine if you are compressing from a source movie clip, as they can just open the file multiple times.


But when you export from Final Cut Pro, FCP can only communicate with one copy of the encoder - it cannot launch multiple copies of itself. Consequently, you cannot export to a virtual cluster from the Send to Compressor command.


A common misconception is that exporting to a QuickTime movie is slower. This is wrong - it is actually faster for two reasons - 1) it is faster to read the file directly than to request each frame from FCP and 2) you have access to virtual clustering. If your timeline is completely or partially rendered, deselect Make Self-Contained and the QuickTime export will be quicker.


Another issue is that you are using up all of your virtual cores, leaving nothing left over for the operating system. There are varying schools of thought on how many to choose, ranging from the total number of cores minus one to half the number of cores (the latter being Apple's official suggestion). Also remember that each instance requires at least 1 GB of RAM, and remember to leave some extra for the OS and running applications.

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