Awful FPS When Video Editing When using the Video Editor mode of Blender 2.82 (I have not used other modes) I get 1-3 FPS max when previewing the video. My processor, GPU and RAM are all no where near maxed out: GPU is at 5%, processor at 30%, RAM around 3 GB out of 8 GB. I can run any game that I download, including heavy games like Assassin's Creedy Odyssey so while my computer has it's limitations, 3 FPS doesn't feel like the ceiling. When I actually render video (not just preview) I ALWAYS get 0.3s to render a frame, regardless of the changes made. There's also a huge lag when dragging videos along the timeline, the actual drag animation lags by up to 5 seconds sometimes. 

What I've done:


I've gone into Preferences and increased Sequencer Cache Limit to 8 GB, but the ram is still not fully utilized. 
I've set system to use OpenCL and use my AMD 5600 XT graphics card, and I've gone to Render Properties and set the Render Engine to Cycles with the supported feature set, GPU compute mode. I've changed tile sizes, experimenting with 1 tile / frame, and using auto tile size. I've used the Eevee render engine as well. All of these changes have absolutely no effect: I still get 1 frame per 0.3 s. 
I've installed the latest drivers for my graphics card. 
I've observed my GPU usage from AMD Radeon software: so I know my GPU is actually at 5%. 


These are all of the suggestions I've seen, and none of them have done anything for me whatsoever. Obviously with free software you're going to experience problems but I don't think it should be unusable on a relatively expensive computer. 

As an additional experiment, I've noticed that if I just load a video in on it's own, and do absolutely nothing to the video, I start with about 18 FPS for under a second and then drop to around 4 FPS for the rest of the preview. The bottom line is that's still way too few frames without anything being maxed out. What settings can I change to resolve this?
In preview mode of the Video Sequence Editor open the properties panel by pressing N on the keyboard. Then check Prefetch frames under the view settings tab. You will see an orange line under track 1 of the sequencer growing until the video has been pre-loaded. Large clips may need more RAM allocated in settings as VSE fetches the video frame by frame.