I cut some MP4 files in LosslessCut. Now I get an error message when trying to edit them in Mp3tag. But I have done this many times before without this beeing an issue. Now all the new files refuse to be written to in Mp3tag. Error message says litt useful. Only “File cannot be opened for writi…

[image] LarsErikOsterud: Is there any way to get som more info on WHY it cannot be written? I had a look at the file and it contains an invalid MP4 atom, which causes Mp3tag to refuse writing to that file. What you can try is loading this file in foobar2000 and use File → Properties and remo…

Do you see an exclamation mark in the first column of the file list? That would mean that MP3tag considers the file to be corrupt. See also here: [image] How to check files for errors? Howto It’s required and often helps to reduce support cycles to check file…

Could you provide one of the files for which you receive the message "File cannot be opened for writing"?

Hmmm… Wonder if the file is intact when uploaded here…. Otherwize I can put it on GoogleDrive and link to it? Edit: I tried to save it from here, and then edit in Mp3tag. Same error. But it plays OK in all players… So I can’t get why it cannont be written.

A check of this file with foobar2000 and optimizing the file layout leads to this response: Suspicious behavior, file became larger instead of shrinking! file://C:\Users\me\Downloads\Jahn Teigen, Anita Skorgan - Adiue.mp4 Old size: 2631436 bytes, new size: 2635524 1 file processed. Total file siz…

If I recode the file in Handbrake then it acts normal. But that will reduce the quality. So that is not an option.

Do you have the file after the foobar2000 optimizing? Does the optimized file act normally in Mp3tag? Then it might be a problem with the newest version of “LosslessCut” (never been a porblem before). What is the easiest app to use to rewrite the MP4 files without recoding anything?

No, the file cannot be modified in MP3tag. But I would try the older version of your program and see if the problem prevails.

Can't access MP4 files

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ohrenkino April 21, 2026, 7:27pm 2

Do you see an exclamation mark in the first column of the file list?
That would mean that MP3tag considers the file to be corrupt.
See also here: