Looking for a reason to actually render in FCP X

So I think I am past the "messing around" with FCP X and actually working in it. But I couldn't help share this.

Actual rendering in FCP X seems very slow. Glacial in fact. Exporting however, at full quality without rendering is super fast (at least it felt that way). So did a little test.

20 second timeline. 5 layers of 1080p, h264. Created optimized media. Color board correction on each, made each move and zoom, etc.

Modify > Render All -- 17.5 minutes

Changed a clip, now the entire timeline shows orange and needing to render:

Share > Export Media - Current Settings (prores) -- 1.5 minute
(I also did a h264 export 1 minute 50 seconds)

Wozers. So I opened AT monitor and saw that the render in FCP X is only CPU, while the export is CPU & GPU. I have an ancient machine (2006 MacPro) so perhaps this is a case of a slow CPU but fast GPU (Radeon 5770).

So for now I don't see any reason to render, or even have background rendering turned on. It's literally 10 times faster in this case to just export without rendering.

I found this a little hard to believe so tried it myself. Similar results - rendering on export is 8 to 10x faster.

Optimised media (prores 422) - 1080 25p from 60D, 5 layers, 20 seconds, color board correction on each, resized top 4 tracks so they filled about 1/6th of the frame but didn't bother zooming etc .

Over 8 minutes to render.

Made a slight change to one layer - orange render bar appears.

Export current settings 1m 5s.

Running on late 2009 iMac, Core 2 Duo 3.06Ghz ( 2 cores) and Radeon HD 4670, so both CPU and GPU relatively slow.

Rendering was using close to 100% of both cores (200% in activity monitor). Export around 80%.

Incidentally un-rendered playback of 5 streams is smooth. Could even adjust saturation of one layer in real time with only a little bit of stuttering.

I've been rendering out of habit - not necessity and somewhat disappointed with the outcome. Good to know about this. Thanks for sharing!

I'm fairly new to FCPX. I bought a fully maxed out i7 iMac to deal with it and I'm loving it so far. This little piece of information is probably the most valuable tip I've come across to date, though, so I thank you very much.

The file is exported without rendering?

Exactly. Try it, you will be shocked at the speed.

I tried, before long, and. Mov was all black, did not show anything. Rendered and exported again and was normal.
What might be happening?
When used the 7 tried this several times, export without the "self conteined", has always given problems.
Is there a leprechaun in my macs!

That's really interesting. When you render as opposed to export it must be doing something differently. As you are working in Native H.264 perhaps it has to transcode each layer before rendering? No sure.

I always transcode on import to ProRes so my render times are very fast. I would think this is the best way to go if you have ample storage to take the larger media files. This way your whole timeline will be much snapper, you won't even notice when it does have to render and outputting happens in the blink of an eye.

AFAIK when FCPX actually renders it renders with CPU and 32-bit floating point accuracy. Also then all the Motion templates are rendered with Best Quality. When you playback in FCPX without rendering it plays with GPU and 16-bit floatint point accuracy and Motion templates are shown with Normal Quality. People working with Motion know the difference between best and normal quality.

So what's the difference. In many cases not that much. If you have Motion template with lots of scaling with texts and objects you get hiqher quality and better looking edges etc. with best quality (meaning rendering in FCPX). Also you might see difference between 16-bit GPU and 32-bit CPU in some extreme color adjustments.

So if you haven't rendered your timeline and just export, it renders your file using GPU and 16-bit floating point accuracy. So basicly quality is poorer than what you get when you first render your timeline and then export. But almost in any cases you really can't see the difference. But that's the reason why it's so much faster just to export and not to render first.

tap5a wrote: So if you haven't rendered your timeline and just export, it renders your file using GPU and 16-bit floating point accuracy.

Did you see this documented somewhere or did you just figure it out? Just curious.

Hi Tpayton,

and thanks for questioning me. Actually it seems that FCPX has changed Motion templates behavior in 10.0.3 which is great! Now Motion templates gets rendered best quality all the time. So there's no visible differences between realtime playback and actually rendering. On pixel level there are some small antialiasing differences but nothing people should care.

Anyway when FCPX actually 'background renders' it renders with CPU and if you check Apple Motion tech specs it says:

• Color bits per channel: 16-bit float for GPU rendering; 32-bit float for background software rendering of Motion projects in Final Cut Pro (float processing requires a graphics card with 256MB of VRAM; 512MB or more recommended).

And as far as I know FCPX and Motion are basicly using same rendering engine so that's why I deeply believe processing is 16-bit float when exporting without first rendering (exporting with GPU). Of course I might be wrong. Anyway background rendering is software only and GPU is much faster for many operations (especially if you don't have some 16 core machine. Then software might be actually faster...) and exporting without rendering is using your GPU.

i have an imac 27" i5 and a MBP 15" 2011 models, and i can see the difference too in time for my render vs export test (various clips , not optimized with effects and titles).

i have FCPX 10.0.3

"32-bit float for background software rendering of Motion projects in Final Cut Pro"

This seems very odd that it should appear like this on the tech specs as Motion projects can no longer be imported into FCP.

"Anyway when FCPX actually 'background renders' it renders with CPU"

Not sure if this is true. Probably depends on what's being rendered. Some effects are GPU reliant.

If you've background rendering turned on (by default it's on) you've propably already rendered everything before you export. Have you turned that off so you see that orange line on top of your timeline where rendering is needed?

Throw for example Curtain generator to timeline and see how long it takes to render on timeline and if you just export it without rendering.

20 sec of Curtain at SD size on my old laptop:

1min 30sec (rendering on timeline)
19 sec (straight export)

Wow, I wasn't aware the difference is that big. Well maybe difference wouldn't be that big on newer multicore machine.

Tom Wolsky wrote: "Not sure if this is true. Probably depends on what's being rendered. Some effects are GPU reliant."

You're right Tom. I opened OpenGL Driver Monitor from Developer tools and noticed GPU Core Utilization is very high when playing back material in FCPX but when I started rendering Motion templates GPU utilization dropped to zero. So Motion templates were rendered only with CPU. But then I tried color correction and noticed that rendering of color correction actually used GPU and also scaling and also some effects. So yes you're right it depends what's being rendered. But when you export without rendering it renders even motion templates with CPU. Interesting...

By not rendering, if FCPX were to crash at any point, would all the progress that has been done still be saved?

Nothing should be lost. Rendering has no effect on the project file.

I do have a reason NOT to render in the background, which I think may have something to do with all the issues 3rd party plug-ins seem to be having lately, and maybe it in fact has something to do with GPU vs CPU. Interesting. Anyway, the issue is this (and I think I've had it on previous versions too): when I grade my footage -- for which I usually employ at least one add-on, such as MBL 2 etc., allow background rendering, and then export, I get really annoying artifacts (green frames, dark frames ....). Also, even on FCP X native effects such as the aforementioned curtain transition, changing parameters on the transition, if for example it is inside a merged clip with a x-fade on top, the pre-rendered bit of the curtain within the xfade does not re-render. And the glitches don't go away until I completely delete all render data.

If you want an example, look at the first few minutes of this: vimeo.com/36502124 (the problem persists throughout, with maybe a dozen such glitches at random moments, not even necessarily on an edit).


I can't speak to whether there is a perceptible quality difference between rendering in background and rendering on export. I do think it is incredibly silly that FCP X won't save the render it does on export into its render data area, but instead the orange bar remains. The old FCP did (or rather, did not do diddly) the same.

Seems to me that there should, must, ought not to be this apparent 16/32 bit discrepancy, it makes no sense and would inevitably cause problems on professional-quality production work. I don't see editors sitting around to bg render that last little change before exporting, if they know they don't need to look at it again before sign-off.