Created attachment 177749 [details]
"INVALID" text displayed in Clip Monitor for existing imported video files, and "INVALID" text displayed in Project Monitor for existing edited clips from editing timeline, when re-opening projects

Chocolatey is not officially supported by the Kdenlive team. Please try the Windows binaries provided on our download page that should work correctly, and report the issue to Chocolatey.

If the problem persists with our binaries, feel free to re-open the issue.

Problem persists on Windows binaries available from the download page, even without Chocolatey.

I just tested on a Windows 11 system (23H2 like you), and everything works fine. Could you try to reset the Kdenlive configuration (in the menu > Help > Reset Configuration).

After that, you can check that the environment page in the Kdenlive settings points to the correct MLT/FFmpeg paths, like in my attached screenshot

Created attachment 177754 [details]
Environment settings page showing correct settings

I have exact same settings on the Environment settings page. I have even uninstalled, re-installed kdenlive, reset the settings, without any success.

Created attachment 177755 [details]
kdenlive environment settings

Are your source videos on another drive than C: ? If yes, can you try copying a video to C: and add it in Kdenlive to see if that makes a difference ?

Created attachment 177756 [details]
Error message "Cannot open file <filepath../filename>" displayed in the project bin, refusing to import the working video files, even from C Drive

Attempted to import from C Drive as well, with same error message. Interestingly, the earlier projects have also been affected, which used to work without any issues, in the previous version.

Can you move the video file to your User's Video folder just to be sure it is not a permission issue in the root C:\ folder

One last thing that would be very helpful is if we could see the Kdenlive debug output. For this, you would need to install the Windows  DebugView utility from Microsoft:
https://learn.microsoft.com/en-us/sysinternals/downloads/debugview

This is a small utility that allows to view system debug output. Open the DebugView App, then start Kdenlive and try to add the file. You should have a lot of debug output in DebugView, then attach the debug info here ( remove any sensitive info like username)

Created attachment 177761 [details]
Moved video file to user's Video folder for debug log generation

Moved the video file to my user Video folder, to rule out it is not a permission issue in the root C:\ folder. Used DebugView utility as per instructions, and generated debug log as per instructions.

DebugView utility debug log generated and uploaded, as per instructions.

This is puzzling. Nothing seems wrong on Kdenlive's side, so my suspicion is an issue  between MLT and FFmpeg, however I  cannot reproduce. I also tried installing Kdenlive from chocolatey and is also works fine. I saw other Windows report that look like yours, so I set the status to confirmed.
I will need you to dig a bit more. Can you please test the following:

Go in the Kdenlive bin folder:
cd C:\Program Files\kdenlive\bin

Run melt.exe (the MLT utiliy) to create a short mp4 file (replace XXX with your user name) :
./melt color:red out=50 -consumer avformat:C:\Users\XXX\test.mp4

It should create a short 2 seconds red color clip called test.mp4.
Can you please paste the output of the command here ?

Thanks in advance

Correction, the melt command should be using the .exe extension for melt:
.\melt.exe color:red out=50 -consumer avformat:C:\Users\XXX\test.mp4

Could be there a conflict between kdenlive v24.12.1 and the "user" installed ffmpeg v7.1.0? What happen if the Windows system path is set and point to ffmpeg v7.1.0 and Kdenlive runs on an older ffmpeg version?

Created attachment 177841 [details]
Output of the command  ./melt color:red out=50 -consumer avformat:C:\Users\XXX\test.mp4

C:\Program Files\kdenlive\bin>.\melt.exe color:red out=50 -consumer avformat:C:\Users\RohitBanerjee-AiElem\test.mp4
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+
|1=-10| |2= -5| |3= -2| |4= -1| |5=  0| |6=  1| |7=  2| |8=  5| |9= 10|
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+
+---------------------------------------------------------------------+
|               H = back 1 minute,  L = forward 1 minute              |
|                 h = previous frame,  l = next frame                 |
|           g = start of clip, j = next clip, k = previous clip       |
|                0 = restart, q = quit, space = play                  |
+---------------------------------------------------------------------+
[libx264 @ 000002bf9a84f640] interlace + weightp is not implemented
[mp4 @ 000002bf9a7f54c0] Timestamps are unset in a packet for stream 1. This is deprecated and will stop working in the future. Fix your code to set the timestamps properly
[mp4 @ 000002bf9a7f54c0] Encoder did not produce proper pts, making some up.

Ok, then can you now test if MLT can playback this created file:

.\melt.exe C:\Users\XXX\test.mp4

Should play the red clip in a window (press 'q' to close the video window)

And then try playing one of your OBS files in the same way:

.\melt.exe your_obs_file.mp4

Does it work ?

.\melt.exe C:\Users\XXX\test.mp4 works successfully, so does my other OBS videos files, which I verified already.

I also tested @emohr 's libe of thought on ffpmeg versions being conflicted. I downloaded the ffmpeg files manually from the repo, and manually overwrote them in the kdenlive folder, as per the instructions mentioned in https://forum.kde.org/viewtopic.php%3Ff=265&t=138533.html . Sadly, it still continues with the same error.

Overwriting the libraries inside kdenlive's folder is typically something that could lead to the error you are seeing. 
However I don't understand how melt can work but not kdenlive.
Just to be sure, can you uninstall kdenlive, completely delete the 'kdenlive' folder in 'C:\Program Files', then reinstall using our official package downloaded from our website.

Then, using a teminal:
cd C:\Program Files\kdenlive\bin
.\kdenlive.exe

Just to be sure that you are running kdenlive installed from our package and not another version installed somewhere else on your drive.

Completely uninstalled kdenlive, completely deleted the 'kdenlive' folder in 'C:\Program Files', confirmed no other version is installed anywhere else on my drive, and then reinstalled the official package downloaded from the website. Launched kdenlive from the terminal exactly as the command below:
cd C:\Program Files\kdenlive\bin
.\kdenlive.exe

Attempted loading the test OBS video file from my user Video folder, to rule out it is not a permission issue in the root C:\ folder.

Problem unfortunately still persists.

Created attachment 177843 [details]
New DebugView utility debug log generated and uploaded, for re-installed instance

Didn't realise that the DebugView was already running in the backend, this time it seems like it had something difference from the last log.

I am running out of ideas :(.
Could you maybe try creating a new Windows user with a very simple name (no dash, no space, no caps), and see if you get the same failure starting Kdenlive from that user account ?

I understand the frustration, I also come from a software development background and can appreciate the efforts to investigate the bug.

However, I believe we are veering away from the actual problem at hand, which has nothing to do with user accounts, folder permissions, or environment variables.

As I have mentioned at least twice now, the issue is with the file loading, since there is an observable defect not just in the new projects being unable to load video files, but also with already prior projects successfully edited on previous version, which now display INVALID on the new version, on both Clip Monitor and the Project Monitor.

A code review on the relevant module(s) can perhaps shed more light. Since I practice and teach management as well, I'm reminded of the Vanilla Icecream story (https://kepner-tregoe.com/blogs/help-my-car-is-allergic-to-vanilla-ice-cream-a-study-in-problem-solving/), in this issue's case.

Can you upload the file "2025-01-08_09-25-24.mp4" somewhere or send it to me by SwissTransfer https://www.swisstransfer.com to my mail address fritzibaby@gmx.net so we can have a look.

(In reply to emohr from comment #27)
> Can you upload the file "2025-01-08_09-25-24.mp4" somewhere or send it to me
> by SwissTransfer https://www.swisstransfer.com to my mail address
> fritzibaby@gmx.net so we can have a look.

I can try and transfer the file, but it is a 170MB file. And I really see no point of sharing the file, since I just confirmed that the defect is not present in the previous version. I am uploading the screenshots of the successful video imports on 23.08.3, 23.08.4, and 23.08.5

Created attachment 177844 [details]
Video successfully imported in 23.08.3

Created attachment 177845 [details]
Video successfully imported in 23.08.4

Created attachment 177846 [details]
Video successfully imported in 23.08.5

Mmh, interesting. That means it has something to do with the switch of Kdenlive to Qt6. The OSB file would be interesting to deeper check with the debugger. SwissTrasnfer can have files up to 50GB.

The thing is that in your DebugView startup log, you have 130 lines like: 
plugin not available: "avfilter.aecho"	

Normally, you should only have like 29 lines of it, because some avfilters are not supported.
This means that MLT cannot correctly load the avformat module (its module interfacing with FFmpeg).
So I agree that the issue is probably not related to your video files, but there is something on your system that prevents MLT to correctly communicate with FFmpeg.

Comparing the 23.x with 24.x installs, I found a difference in the way MLT libraries are installed. In 23.08, the 2 MLT libraries
libmlt-7.dll and libmlt++-7.dll were in 2 locations: 
C:\Program Files\kdenlive\bin and
C:\Program Files\kdenlive\lib

In Kdenlive 24.x, these 2 libraries are only in:
C:\Program Files\kdenlive\bin

Could you try with a Kdenlive 24.12 install to copy these 2 libraries from C:\Program Files\kdenlive\bin to C:\Program Files\kdenlive\lib
and check if it makes a difference ?

(In reply to Jean-Baptiste Mardelle from comment #33)
> Comparing the 23.x with 24.x installs, I found a difference in the way MLT
> libraries are installed. In 23.08, the 2 MLT libraries
> libmlt-7.dll and libmlt++-7.dll were in 2 locations: 
> C:\Program Files\kdenlive\bin and
> C:\Program Files\kdenlive\lib
> 
> In Kdenlive 24.x, these 2 libraries are only in:
> C:\Program Files\kdenlive\bin
> 
> Could you try with a Kdenlive 24.12 install to copy these 2 libraries from
> C:\Program Files\kdenlive\bin to C:\Program Files\kdenlive\lib
> and check if it makes a difference ?

Tried this approach, no success.

(In reply to emohr from comment #32)
> Mmh, interesting. That means it has something to do with the switch of
> Kdenlive to Qt6.

This may something to start looking at ...

I similar issue on Windows here (Bug 498237): in 23.8.05 it works in later versions not.

It’s maybe a stupid idea. Update your graphic card driver to the latest version. Maybe that fixes the connection to FFMPEG.