"Why is my computer having troubles editing video"
----This post is going to draw all kinds of responses for sure but I'm talking from experience and lessons learnt.----
I've seen this same comments for about the last 10 years and to go along with that a ton of responses to the problem ranging from GPU's drivers, SSD's ect, etc etc. I know it's hard for some to understand why a 1500$ Mac/PC won't edit smoothly or as they progress the troubles become more pronounced.
The truth is that editing videos is one of the most intense things that you will ever do on your machine and let's face it....MOST casual users don't have machines that are made to edit video.
The response I see most is CPU and GPU questions. The truth is there is a ton more involved...like storage space, over heating, corrupt registry's, fragged storage, memory, anti-virus, websites uploading malicious elements , etc, etc, etc. This is a small sliver of the many things that can effect performance.
This problem is not just a Hitfilm problem. It happens with every software from FCP, Motion, After Effects, Premier, Lightworks, Pinnacle, etc etc etc.
So....speaking from experience when I used a low cost ($2000.00) PC and Mac.
(1) Start by defragmenting your hard drives...REGULARLY.
(2) make sure you have enough free space on the HD....at least 15% free.
(3) Don't browse unknown websites.
(4) If you're editing videos seriously have a dedicated machine just for the purpose. Don't browse websites, don't install conflicting software, don't play games...use the machine for what you want it to do. VIDEO editing!!
I have a dedicated PC sitting to my right now. It does nothing but editing. No browsing, no gaming....JUST VIDEO. It runs like a champ. I do regular maintenance all the time. While my 2 MAC's'OK" for edits without a ton of VFX they are still slow compared to my dedicated PC. If I'm serious I use the PC.
Here is a good analogy - I splice fiber for a living and there are about 15 manufactures of Electric Arc Fusion splicers...ranging from 5K to 35K BUT there is only ONE that preforms flawlessly..and it runs 25K. The rest are mediocre by comparison. I'm serious about fiber splicing and have learnt a lot the past 25 years- if you buy cheap you get what you pay for...low performance - loosing project(s) and reputation because the quality of work is sub-par. Network operators are serious about their performance and so am I.
- I purposely didn't touch on transcoding, GPU, Ram, CPU etc, etc...that's been beat to death already and I have nothing to add to the advice already given.
If you want to edit video without issue then spend the money - if you want to game, browse websites, install all kinds of software, etc. etc. then you are going to have problems and you are going to have to live with poor performance. Period.
It's not the softwares fault - it's yours.
Don't beat me up to bad folks- this is just my 2 cents derived from my experience since 1984 with everything from a TRS-80(trash 80's), Commodores (Amiga), Mac's and PC's