I have a Windows 11 ASUS PC, running the latest version of Shotcut (25.12.31), and no matter what I try, the entire UI is laggy/choppy whenever I try playing a video. Here are most of the things I tried (as far as I can remember right now, probably have tried even more things, also these aren’t in chronological order):
Preview scaling
Using Proxy
Switched audio API from Waveform Audio to DirectSound (seemed to work for a few minutes, then back to lagging again)
Uninstalled OBS Studio (seemed to work for a few minutes, then back to lagging again)
Buying an entire GPU (Nvidia GT 1030, big upgrade from Intel i5 integrated 730, seemed to work for a few minutes, then back to lagging again)
Installing Shotcut as a zip and running portably
Enabling/disabling GPU effects
After extensive research online, I know many people have had this same issue over the years, yet none of them have been solved or ever come to a conclusion. Keep in mind that Shotcut has always run perfectly fine on my Windows 11 ASUS laptop, even playing 4k30fps videos effortlessly without any proxy or preview scaling. While I can edit fine on my laptop, I really think editing on my PC “should” be better. Every video player, like VLC or the built-in one, always plays videos perfectly fine, regardless of the resolution.
I’m hoping to finally get down to a real solution here that everyone can apply to fix this issue. I’m going to try DaVinci Resolve tonight just to see if that also has the same issues.
I have a Windows 11 machine with NVIDIA RTX 4070, and I do not have this problem. I suspect something installed as a Windows system extension is causing a problem, but it is very hard to say what. A while ago, people reported that Grammerly caused a problem. Probably people should be very wary to install system extensions, but it is often not obvious.
You can setup a bootable Linux USB drive and boot into that to try Shotcut there to see how it behaves. It would be nice if you could do that for Windows. Maybe if you have a spare hard drive, you can make a fresh install of Windows to it as a test.
If you think a Windows system extension could cause it, numerous possible ones could be causing it. How could I ever know which one specifically? Also, was GPU processing removed in the latest version? If so, how would I use my GPU for Shotcut in terms of faster processing?
Since the entire UI is lagging, I suspect it could be a RAM issue, due to it spiking to 97% during video playback. After manually setting virtual memory on my PC, things seem quite a bit better. 67% RAM usage, and videos can play, but only at around 20fps (proxy + 720p preview scaling). What I don’t understand is why I’m having this issue with 16GB of RAM (should be able to handle 4k video, right?).
EDIT: At 360p preview scaling and proxy, the video playback is buttery smooth, only mostly though. For some reason, sometimes when I hit play, it lags, and I can hear my PC fans throttle immediately before calming down again after pausing.
Alright, I have confidently come to the root of the issue, but I still need help on how to solve it.
I noticed that whenever the video playback and UI is laggy, when I try changing ANY playback setting in Shotcut, everything instantly runs perfectly smooth again, but only temporarily. If I keep changing random playback settings constantly, everything runs perfectly fine. Now what this tells me is that playback pipeline buffers, frame buffers, audio buffers, or decoding threads aren’t being flushed properly. Since changing any playback setting automatically flushes all of those things, video playback is temporarily smooth, until I pause the video and try playing it again after a few minutes.
A few words from ChatGPT:
What This Confirms About Your System
The hardware can play the video perfectly (CPU + GPU are fine)
The lag is purely due to UI thread starvation + memory/cache growth
Resetting the playback pipeline flushes these buffers → smooth video
Why It Degrades Again Over Time
Even after resetting via player settings:
Shotcut’s internal cache grows as you play more frames
What are the hardware specs of the laptop that works versus the PC that doesn’t? And what video stream format are the source video files? H.264, HEVC, etc
Hello Austin, thank you for taking your time to reply!
Here are my full laptop specs:
OS Name Microsoft Windows 11 Home Single Language
Version 10.0.26100 Build 26100
System Model Vivobook_ASUSLaptop X1605ZA_X1605ZA
System Type x64-based PC
Processor 12th Gen Intel(R) Core™ i5-1235U, 1300 Mhz, 10 Core(s), 12 Logical Processor(s)
Installed Physical Memory (RAM) 16.0 GB
I will add another reply soon so that I can easily copy and paste PC specs from from my PC instead of trying to do it from my laptop.
As for the video stream format, I’ve tried mp4, MOV (straight from my camera), and I think HEVC (from a phone, with variable framerate converted by Shotcut to constant before using it), all with the same results.
I tried 4k30fps, 1080p30fps, 720p, all with the same results. None lagged more or less than the other.
As for PC specs:
OS Name Microsoft Windows 11 Home Single Language
Version 10.0.26200 Build 26200
System Model ASUS EXPERTCENTER D500MD_D500SD
System Type x64-based PC
Processor 12th Gen Intel(R) Core™ i5-12400, 2500 Mhz, 6 Core(s), 12 Logical Processor(s)
Installed Physical Memory (RAM) 16.0 GB
Alright, here’s the application log. So first I just played the video once and that worked fine. Next I replayed it but this time clicked on another app window on my PC, then clicked back onto Shotcut, and it immediately started lagging again: ShotcutApplicationLog.txt (39.6 KB)
Thanks for sharing the application log. Unfortunately, I don’t see any clues in the log about a problem. The log also does not indicate that you tried to play anything. So maybe you just opened Shotcut and immediately saved the log before experiencing the problem. I was hoping that the log would show some messages from while the video is trying to play.
This is usually an indication of system resource limitations. There is common advice that you will come across on this forum where people suggest to close other applications while you are editing if you suffer from poor playback performance. It could either be limited access to RAM, CPU cores being used for other applications, or, if your files are stored on a spinning hard drive, the slow access to the files. But your case seems to be an extreme example and I do not know if closing applications would free enough resources to make any difference.
Thank you for your reply. I’m using a 500GB NVMe and 16GB of RAM, perhaps I need more RAM? But then again for me it’s not about the video resolution, any resolution (even 480p for example) gets super laggy at times. By the way, when I said my laptop works fine, I wasn’t exactly true, it never has any problems editing any videos with preview scaling, but no it can’t edit straight up 4K video smoothly. Another thing to consider though is that my PC CPU has 6 cores while my laptop has 10.
The lag is so bad, I would almost just call it “application freezing”. I was going to suggest trying a different video card and different audio APIs. But it seems like you already tried those things.
Yeah I’d agree on that, because it’s the whole Shotcut application that’s lagging. What do you mean by video card? Never heard of that. Maybe there’s a specific combination of video card and audio API that’ll work fully on my PC?