Blender (and others) video editing: slow and/or bumpy playback - 100% CPU load

I use Blender for Video editing on Ubuntu 18.04, and whenever I playback the video I’m working on, the CPU load hits 100% and the playback is slow or bumpy or both.

This happens even if there is only one video strip in the timeline, with no effects at all, so it’s a simple playback that any media player (e.g. VLC, parole...) can do with no problems, but blender obviously can’t.

I tried different video editors. Openshot has the same playback issue. Kdenlive does a fluent playback but tends to crash, and Avidemux does a fluent playback but is not powerful enough.

CPU: AMD A8-7600 Radeon R7 RAM 3500MB Kernel version: 4.15.0-54-lowlatency

What’s wrong here?

thank you

Ole

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