Thanks for your report. We will need a bit more details to help you there.
How did you install Kdenlive ? Are you using the official Ubuntu package ? Which Kdenlive version is it ?
Could you try our AppImage ? You can download it from here:
https://download.kde.org/stable/kdenlive/25.08/linux/

Then make the file executable and run it.
If the problem persists, please post a screenshot of the exact error message you see.

Created attachment 184662 [details]
Screenshot from 2025-09-03 09-38-13.png

Hi Jean-Baptiste

My Ubuntu OS came pre-installed on the computer and has been updated to 
24.04.3 LTS
I installed Kdenlive through the Ubuntu App Centre Snap package which 
offered me version 25.08.0.
However the  Kdenlive version which was installed is 25.11.70

I've downloaded and run the AppImage and kdenlive is still version 
25.11.70 but now gives a new message.
"The following clips are not usable for editing. This will transcode 
them in an edit friendly format and replace the original ones in your 
project." and below it says "File padddington-video.mp4 has a variable 
frame rate" "Convert to lossy x264 I frame only (VAAPI GPU)". I've 
attached a screenshot.

I don't want to lose the original video copied from YouTube which plays 
fine in Ubuntu Videos and there is a choice of six VAAPI formats and I 
have no idea why it chose this particular one.

Cheers
Barry Sharples
PS I am away in a couple of hours until Saturday so unless you can get 
back to me before, could you put me on hold until then. Thanks.

Created attachment 184852 [details]
Screenshot from 2025-09-03 09-38-13.png

Hi Jean-Baptiste

I'm back again.

To recap:
/My Ubuntu OS came pre-installed on the computer and has been updated to 
24.04.3 LTS
I installed Kdenlive through the Ubuntu App Centre Snap package which 
offered me version 25.08.0.
However the  Kdenlive version which was installed is 25.11.70

I've downloaded and run the AppImage and kdenlive is still version 
25.11.70 but now gives a new message.
"The following clips are not usable for editing. This will transcode 
them in an edit friendly format and replace the original ones in your 
project." and below it says "File padddington-video.mp4 has a variable 
frame rate" "Convert to lossy x264 I frame only (VAAPI GPU)". I've 
attached a screenshot.

I don't want to lose the original video copied from YouTube which plays 
fine in Ubuntu Videos and there is a choice of six VAAPI formats and I 
have no idea why it chose this particular one./

My bug query was why I received a 'File corrupted' message instead of 
the offer to transcode the video from VFR to CFR which it now shows.  
The other question which you might be able to point me to an answer is, 
what are all these VAAPI formats and could Kdenlive indicate which is 
the default on its menu?

Cheers
Barry Sharples

🐛🧹 ⚠️ This bug has been in NEEDSINFO status with no change for at least 15 days. Please provide the requested information, then set the bug status to REPORTED. If there is no change for at least 30 days, it will be automatically closed as RESOLVED WORKSFORME.

For more information about our bug triaging procedures, please read https://community.kde.org/Guidelines_and_HOWTOs/Bug_triaging.

Thank you for helping us make KDE software even better for everyone!

Still getting messages like this -  Cannot open the project file. Error: Cannot open file home/user/Downloads/ipad-bounce-solved.mp4: (line1, col 1)  The file plays fine in Ubuntu Videos and VLC Player.  Unfortuantely I can't open it to edit in kdenlive. Doesn't even go on about converting from variable frame rate to fixed frame rate, just refuses to open the video file. I really would like to work with kdenlive in Ubuntu.

🐛🧹 ⚠️ This bug has been in NEEDSINFO status with no change for at least 15 days. Please provide the requested information, then set the bug status to REPORTED. If there is no change for at least 30 days, it will be automatically closed as RESOLVED WORKSFORME.

For more information about our bug triaging procedures, please read https://community.kde.org/Guidelines_and_HOWTOs/Bug_triaging.

Thank you for helping us make KDE software even better for everyone!

🐛🧹 This bug has been in NEEDSINFO status with no change for at least 30 days. Closing as RESOLVED WORKSFORME.