Why Does the Render Cache turn red after an insert edit?

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EricLalicata

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Why Does the Render Cache turn red after an insert edit?

PostMon Aug 08, 2022 7:05 pm

Maybe I am doing something wrong.

We have a fully render cached timeline with a lot of noise reduction etc pre-cached for playback.

We insert edit a new logo at the top of the timeline and the entire timeline cache turns red.

Why?

Isn't the cache tied to the clip? Why would moving the location of the clip on the timeline make the cache disappear? Shouldn't Resolve know to keep the render cache tied to the clip based on it's source frame timecode? If not, can it be changed to do this?

Thanks.
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Jim Simon

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Re: Why Does the Render Cache turn red after an insert edit?

PostTue Aug 09, 2022 2:04 pm

With a brief test, I couldn't duplicate this in Studio 18.0.1 on Windows 10.
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joema4

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Re: Why Does the Render Cache turn red after an insert edit?

PostWed Aug 10, 2022 2:03 am

EricLalicata wrote:...fully render cached timeline with a lot of noise reduction etc pre-cached for playback...We insert edit a new logo at the top of the timeline and the entire timeline cache turns red. Why?..Isn't the cache tied to the clip? Why would moving the location of the clip on the timeline make the cache disappear? Shouldn't Resolve know to keep the render cache tied to the clip based on it's source frame timecode? If not, can it be changed to do this?...


There are three categories of cache: Source Cache (now called Fusion Output Cache), Node Cache and Sequence Cache. They each can be invalidated without affecting the others. The goal is enable you to adjust an edit without affecting the cached grade, and vice versa.

Unfortunately the red/blue render bars are not specific to which category of cache is valid. IOW you can do an action that invalidates sequence cache that might have a limited performance impact and the render bar turns red. Or you could do an action that invalidates node cache on a clip with noise reduction, which has a great performance impact yet the render bar turns the same red color. The UI unfortunately does not distinguish which type of cache is valid or not. However you can often deduce this by the time required to re-render. If slow, it is more likely node cache for a compute-intensive effect. If fast, it is maybe sequence cache.

I set up a timeline and put some titles and various effects on it including temporal/spatial noise reduction plus burn-in timecode. If I inserted a .jpg at the start of the timeline, certain portions of the timeline would briefly show red render bars. However that was apparently just rebuilding sequence cache, not node cache.

On my timeline it only did that for regions of the timeline containing multiple layers and only for certain types of effects. For what it's worth, on page 182 the Resolve 18 manual says: "Sequence Cache is a separate cache for effects that are specifically applied within the Timeline in the Edit page. These include transitions, opacity adjustments, and composite mode superimpositions."
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EricLalicata

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Re: Why Does the Render Cache turn red after an insert edit?

PostTue Sep 06, 2022 8:25 pm

Thank you for your replies. It seems that it is the sequence cache that disappears when this happens. It also seems that it does not happen all the time. We also find that when all the "Automatically Cache..." checkboxes are checked in the cache preferences, and the render cache is set to Auto, then often times the entire timeline turns red. For no apparent reason. We get full playback without the render cache, so we are not sure why it is rendering.

But if we uncheck the "Automatically Cache..." check boxes and use the "User" mode for render cache, then we can select the clips we want to render.

Seems to not function the way I expect it to. So not sure if I need to manage my expectations on the reality of this, or we are doing something wrong.

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