Big delay switching between source & timeline

First of all, my hat off to the creators of Shotcut! I was a professional video editor for 30 years, and I’m blown away by what an amazing program you’ve managed to create and keep improving!
However, one thing frustrates me a lot: a delay of 5 to 10 seconds (sometimes more) whenever I switch between Source and Project preview, and also whenever I grab a clip on the timeline to move it, trim it or replace it. I had huge issues before with stuttering preview playback during editing but those got solved (largely) when I switched to proxy editing. I do have a lot of sources: I’m making a 12-15 min puppet short film for which I’ve shot over 1300 clips, most of them around 10 to 15 seconds long. I’ve already edited the main segment (about 9’30”), and am now replacing shots here and there, tightening things up and adding a beginning and ending sequence, as well as credits (eventually). I’ve got one video track, plus one for the opening title, and 5 audio tracks with lots of sound effects and a bit of music; I don’t use the on-camera sound so I’ve muted the video clips. All the video currently in my project has been converted to proxies. I avoid using video thumbnails or audio waveforms. Shotcut hardly seems to use memory at all during, but there are big spikes in CPU activity. The editing is so tedious that I’m not sure if I can finish this project on Shotcut or have to look for another solution. Any ideas what I can do to improve the situation? Do I need a better computer, or will that not really help?

My system: HP Pavilion desktop 550-019, AMD A10-7800 Radeon R7, 12 cores 4C+8G, 3.5 GHz; 8 Gb RAM; Windows 8.1 (64 bit)

Looking up your computer on HP’s website, it shows you are using 1 single Hard Disk Drive for everything. This one sole hard drive is operating Windows 8.1 and everything else on your computer while processing your video at the same time. Installing an SSD as a second drive and only operate Shotcut from that drive, along with all of your media files used for your project to that drive will greatly increase the speed. And if you ever decide to buy another computer, you can use that same SSD in your new computer.

If you have other programs open on your computer, including running anti-virus, that will also slow down your computer and increase your CPU usage. If your CPU gets too hot, there is internal software that will kick in to slow your computer down as well. Video editing is a very CPU intensive process.

There are also issues that could slow things down as with filters, and the video mode to source clip resolution & FPS specifications that could contribute towards having it be so slow.

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Thank you for your response. I forgot to mention that I have added an SSD drive, which I use only for my Shotcut media. I’ve tried running the standalone version of Shotcut from it, as well as the fully installed version on my regular harddrive, but it doesn’t seem to make a difference where I run the program itself from. I’ve tried shutting down everything I could, but that too makes little difference. As I said, working with proxies (with preview scaling on or without) helps a lot with everything else, but not with the delays I’ve described. As for filters, I’ve used dissolves and fades here and there, and tweaked the colour of a few shots, but nothing major. And I’ve added one title at the beginning…

Which version of Shotcut are you using? (Help - About Shotcut)
How hot is your CPU getting when you experience these delays?
What is your video mode? (Click on Output, the Properties)
Is there a specific clip that is causing delays? If so what is that clip properties? (Click on that clip, then Properties).

Are you running Anti-Virus programs?

Shotcut version 21.05.18 (I tried the last stable version as well but no difference).
CPU temperature is normal (15 degrees C).
No antivirus – just Windows Defender. No background processes other than Windows stuff.
All my video is 1080p 23.98fps, but as I said I’m working with proxies generated by Shotcut (same frame rate, 960x540).
The same delay affects all the clips. If I select a different clip in the playlist, I have to wait for it to become activated. If I switch between source and project, I have to wait. Every time I click on any clip in the timeline, it takes 5 or 6 seconds for the red outline to appear around it so I can do something with it. Ripple on or off, magnet on or off, all audio tracks muted or not – doesn’t make a difference.

What? It’s too cold. An healthy or normal temperature of a CPU is 50°C.

I think this much low temperature is causing some problems.

And 15°C is very hard to get, until you put you PC totally in ice cold water… :rofl::rofl:… (I have putted a rofl emoji, but seriously it is only possible when you put your PC in ice cold water totally).

Ha ha, yes! I checked the temperature with CoreTemp, and that’s what it says for core temp. :cold_face: Maybe it’s confused because I’ve got CPU virtualization enabled so the 4 processors act as one? In any case, I don’t get any overheating warnings and the fans are working properly, so I don’t think that’s the problem.
I just discovered though that only 6.95 of my 16 Gb of RAM are shown as usable. I tried a few different configurations and only one RAM slot seems to be working. Maybe I’ve got a bad motherboard, which would explain my problems…
I also wonder if adding a graphics card would help, so that it would take over some of the processing? I don’t know if that would make a difference for editing, or only for exporting (I don’t care so much about the time it takes for that).

Filters are currently not optimized for GPU. Editing speed is almost entirely dependent on the CPU. Adding a graphics card generally only helps for exporting speed.

Okay, that’s great to know. Thank you!