Intermittent freezes/not responding for up to 30s when selecting filters that use file paths and a mapped network drive is unreachable (Windows)

NOTE: I’m posting this mostly for awareness because I believe this is a Windows-level problem as even the explorer window sometimes hangs during refreshes for up to 30s when enumerating drives (and also there’s plenty of reports of mapped drives related issues on the net (example).

This is one of those bugs that’s been haunting me intermittently for at least a year but I could never get a reliable reproduction yet obviously it wasn’t very common as there were not many posts on the forum about it (there are 2 about freezing altough I’m not sure they match the same cause).

Last weekend, when I was randomly editing a project and my NAS got an OS update so it had to reboot (note: all files for this project were local only) and almost immediately after I heard the NAS reboot sound, Shotcut started not responding/freezing when opening the filter panel for up to 30s at a time, then it completely returned to normal and the freeze would happen again after a few minutes. Only after the NAS finished the update and went back online has this stopped completely. This is when everything clicked for me on what was the trigger.

What is your operating system?
Windows 10

What is your Shotcut version (see Help > About Shotcut)? Is it 32-bit?
22.10.25 (also in 21.08.11, the oldest version I had around)

Can you repeat the problem? If so, what are the steps?

  1. Open Windows Explorer and navigate to a NAS location (must be by IP not a DNS name, I use this format: \\192.168.0.xx) and right click on a root shared folder → Map network drive, choose a drive letter and click finish (the drive should now appear in Computer along with the regular ones)
  2. start a new project, add 2 color clips (5s each) and put on both of them any filter that can open files (I’ll exemplify with LUT (3D) as it’s older, but I’ve reproduced it mostly with GPS graphic)
  3. (just to confirm everything is stable now) select deselect each of the two clips hit play etc.
  4. unplug the network cable from the NAS (or make it unreachable in some other way). Check in Computer to confirm it is unreachable with a big red X.
  5. go back into Shotcut and click on one of the clips with the LUT (3D) filter applied on it. Shotcut window should immediately stop responding for almost 30s with the filter panel being completely blank. Unless you continue clicking on the shotcut window or press the red X, it should not crash, simply starts working again after this timeout.
    After one freeze, it seems there’s a minute or so of “immunity” but, at least for me, it is guaranteed to freeze again after a while (I just click back and forth between the 2 subclips so the filter panel is refreshed and I can see the freeze again).
  6. If I connect back the cable to the NAS, within seconds the issue disappears.

Note that at no point I have loaded any file into any filter. Also there is no video/image anything loaded in the project so it isn’t trying to connect to the mapped drive. I suspect the issue is behind the scenes in QT when the filter code that deals with file paths is encountered QT probably does a query of all available drives by default and has to wait for the Windows results.
2022.11.01 - test bug.mlt (3.8 KB)

If anyone has a NAS or something to test this I’d appreciate it to confirm whether it’s a general issue or just me.

So I’m guessing there’s nothing in your event viewer logs, but have you tried something like:
NetFlow Traffic Analyser, PRTG, or Wireshark?

Iirc you are a programmer, or at least have programming skills, so Wireshark should be no problem (even though the first two have much much better user interfaces and I’d go with PRTG on windows, since it installs as the full version and you get 30 days before it auto reverts to the freebie).

Maybe worth a try?

Edit: I just tested with my NAS on Linux and no issues with Shotcut. Will reboot into Windows 10 later and give it a whirl.

Shotcut’s autosave feature runs about once every 30 seconds and I believe the mechanism Shotcut uses will essentially SAVE the file each time. There appears to be a Windows (freeze) problem if a NAS folder is in the Windows “Quick Access” folder and the NAS is unavailable. There is a workaround in the post on below:

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I didn’t think about those, nothing in the event viewer. I’m only familiar with Wireshark and it seems to show a bunch of MDNS and LLMNR name queries for the NAS when shotcut freezes, so my theory that Windows queries all available devices seems to stand. But weirdly I only see queries for it’s name, nothing for the IP.

When the NAS is reachable there’s a bunch of SMB2 create request/response get info file whenever I click on the LUT filter (but only once every minute or so, just like when the freeze is there, it doesn’t happen for every click). These SMB2 requests don’t appear to be present when the IP is unreachable (but I’m not 100% sure about this, I still saw them once but after restarting capture they aren’t there anymore).

I don’t have any NAS folders pinned in the quick access folder, but the mapped drives are there, next to my HDDs below the Computer category. Altough I don’t think it is related to this issue or autosave at all, if I don’t have any of the “problem” filters I never have the freeze. And even with the filters added to some clips, it only freezes when I literally open the filter panel with that particular filter present, otherwise there is never a problem and Shotcut runs very smooth.

Thanks to both of you for looking into this!

Looks like @Elusien has the answer (I hope!). I can imagine how annoying that would be.

I just now tested the quick access options suggested by the superuser post but no luck, I unplugged the nas and first time I click on the clip it freezes again.

The thing is now it’s ok, because I know the cause and I have a workaround: I simply delete the mapped network drives from my computer when I have the NAS shut down and that’s it. I do have to recreate them again next time I need them but I only have 3 and to be honest it’s a very small price to pay considering the alternative.

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Buggar. OK, well are you scripting that process?

Attached a sample bat file as a zip since forum was stripping back slashes. (554 Bytes)

Something like that as a .bat file should work just fine without any manual intervention.

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Now that you said it it is very obvious I should have used a script instead of storing the 3 commands in a text file :sweat_smile:… thank you!
It seems to do the job really nice, just had to change the NAS ip to IP+folder as the root would return false but other than that it’s golden :wink:

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Very good, glad to hear it. I already knew you were smart enough to figure out the modifications so didn’t even mention it :smiley:

P.S It was untested so I thought there might be a typo or slight error that you needed to rectify. I’m almost impressed I didn’t f*ck that up!

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There is nothing we can do about this. It’s an old Windows problem and not specific to Shotcut or Qt.

Thanks for confirming it, I assumed it was the case.

Indeed, code that compiles/runs the first time is always impressive :smiley:

Indeed, which is probably why it ran first time (since that little snippet barely qualifies as anything resembling code)! At least it will prove useful now that you know there isn’t a solution.

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