APPLE FINAL CUT PRO: Apple Final Cut Pro X FCPX Debates FCP Legacy FCP Tutorials

Re: Rendering files

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Joe Marler
Re: Rendering files
on Aug 15, 2017 at 11:44:53 am

[Simon Billington] "there seems to be some redundancy to how FCPX renders versus what it exports, especially if its in the same format....Since ProRes is a form of compression, even if it's lossless, it may involve quite bit of decoding and re-encoding just to update a specific change. It may have a negative impact on the performance. So FCPX just renders the file fully instead.... It may actually be possible to achieve more effecting rendering when outputting in the same format as you edit, but the devs either never thought of implementing it, or maybe its just not high enough on their list of priorities."

In general FCPX does "smart rendering", IOW if the timeline (or portions thereof) are already rendered, it does not blindly re-render that when exporting. This is regardless of whether the timeline is H264, ProRes or H264 which was transcoded to optimized media, and regardless of whether export codec is H264 or ProRes.

This can be easily seen by applying a simple color correction effect which causes the timeline to go non-rendered, then exporting it immediately, then after pre-rendering it (CTRL-R). Whether using optimized media or H264 and whether exporting to ProRes or H264, it exports faster if the timeline is pre-rendered.

This doesn't mean that pre-rendering should be the standard practice or that background rendering is required. In general FCPX exports so fast that these usually aren't needed. However if the timeline or portions of it are pre-rendered, then FCPX will use that during export and not blindly re-render it.

There may be more complex effects cases where this isn't done but in general FCPX uses smart rendering.

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