Can’t Play Back Even When Rendered

[Doug Metz]

Does it improve anything if you hide the inspector?

Doug Metz

Dalton Agency

[Joe Marler]

[Brett Sherman] “I’ve been having problems with complicated, graphical timelines being unable to playback. I’m using some relatively complicated Motion templates. I get why it won’t playback even remotely close to real time when not rendered. But what I don’t get is why after it is rendered it still won’t play back”

If the timeline is fully rendered you’d normally expect it to play back smoothly. All effects and codecs are rendered to a set of cached render frames, by default ProRes 422.

However — there are some cases where FCPX does not properly use the cached render files. These involve some built-in and 3rd party effects, and combinations of them in the stack. Many effects are internally implemented as Motion templates so that might be a common element.

In my testing there are “well behaved” and “poorly behaved” effects regarding the impact on re-use of cached render files. In an extreme case certain built-in effects can prevent cached re-use of render files from highly compute-intensive effects such as Neat Video. This can have an extremely severe performance impact. In some situations the render dots do not properly indicate whether valid render files exist or will be used.

There are different states with varying behavior. In some cases just rebooting FCPX will change the behavior. In other cases, re-rendering the timeline will help, but in other cases not. The entire system of tracking and using render files and the relationship to various effects needs to be examined by Apple and either fixed or documented.

I don’t know the internals of the Motion run-time engine. It might be that due to run time processing, not all templates can be pre-computed and cached. However to my knowledge none of that has been documented.

The simplest thing to try is disable background rendering, delete all render files, do a one-time render of the timeline with CMD+A and CTRL+R, re-launch FCPX, render the timeline again if any ranges require this, THEN try your edit action or export.

In some cases this procedure will help. In other cases the slow performance will be persistent. In that case you need to examine the effects stack for the clip in the slow timeline region. As an experiment remove any known “poorly behaved” effects. In the below post I list some of these but it’s not comprehensive.

https://www.fcp.co/forum/4-final-cut-pro-x-fcpx/31621-help-losing-renders-after-fcpx-close-or-project-switch

[Brett Sherman]

I did the following things which had no effect:

– deleted cache file to force re-render
– created new library and dragged project into it
– hid inspector
– made into compound clip

I would say that it’s unlikely it has to do with particular render files because I’ve re-rendered I think about 5 times now from scratch. It must have something to do with FCP X “loading” the Motion templates when it hits a particularly intensive section.

I’ve tried all sorts of things to isolate. As much as I can tell it has to do with hitting a certain threshold of Motion template loading. I can exceed it with different templates in different combinations. One particular title template I made seems to be causing most of it. The crazy thing is I can use instances of the same title in other less layered sections and it works fine – if a bit sluggish.