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VSE Low Playback Rate: Show Cache On will cause a lower fps
Closed, ResolvedPublicBUG


System Information
Operating system: Windows-10-10.0.17763 64 Bits
Graphics card: Intel(R) UHD Graphics 600 Intel 4.5.0 - Build

Blender Version
Broken: version: 2.80 (sub 75), branch: master, commit date: 2019-07-29 14:47, hash: rBf6cb5f54494e

Having Show Cache On will give a lower fps(gif):

Play a heavy video clip in the VSE and notice the difference in frame rate when switching the Show Cache on/off.

Event Timeline

Brecht Van Lommel (brecht) lowered the priority of this task from 90 to 30.Sep 25 2019, 12:35 PM

Please use the template and provide all the requested information, even if you're a developer.

Brecht Van Lommel (brecht) raised the priority of this task from 30 to 90.Sep 25 2019, 3:01 PM

Could we have Show Cache switched off as the default setting until this is resolved?

Not sure of cost vs. benefit here. Performance loss is nowhere near cross vs alpha over.

most likely on recent machines not even noticable

Well, users shouldn't have to deal with cache in the first place - is should work unnoticeable - so being able watch the cache working is imo mainly a developer/debugging tool - and therefore should be off as the default setting.

That said, the slow playback performance of the VSE is a real problem, and has always been. You will not find any video editor out there with a slower playback rate than Blender. Not dealing with regressions which makes the playback even worse is imo not the way to attract more users.

It should also be noted that this regression multiplies, when adding more instances of the Sequencer area: T69927

Richard Antalik (ISS) raised the priority of this task from Low to High.Tue, Jan 21, 3:03 PM
Richard Antalik (ISS) changed the subtype of this task from "Report" to "Bug".

I think it makes some sense to disable the cache visualization by default if it really has a significant performance impact.

In principle it should be possible to make drawing it really fast. For OpenGL it might be most efficient to allocate a 1D texture and draw it with nearest interpolation. Updating only the part that changed is possible as well. But it's not a trivial change.

Having the "Show Cache" on actually causes a serious drop in fps over time - in ca. 20 sec 40 fps are lost(from 60 fps to 20 fps) - looks like a regression?
This does not happen when "Show Cache" is off.

As requested by @Peter Fog (tintwotin) :

Data sourced from

This is a snippet from Spring.


Cache on ~100fps
Cache off ~130fps

Thanks for data,

I have patch almost ready for quite some time.. I just need to find shader for drawing - it wasn't immediately obvious how to do it.