EXIF tags unchanged in mp4 files

[conr]

Current version for Windows of ExifTool (as many older versions) is not able to modify at least some "writable" "string" EXIF tags of at least some mp4 files despite being able to read them.

Example:
> exiftool.exe "-EXIF:DateTimeOriginal +=1:0:0 0:0:0" *.mp4
    0 image files updated
    1 image files unchanged

> exiftool.exe "-EXIF:DateTimeOriginal" *.mp4
Date/Time Original              : 2022:02:17 15:41:13

Files were generated by Canon Camera and contain many QuickTime an MakerNotes tags which are displayed and edited correctly. Some of QuickTime tags duplicate functionality of EXIF tags.

EXIF tags are easily editable in hex editor, and recognized by ExifTool after such modification.

Similar tags with the same encoding (plain text as checked in hex editor) are working in JPEG files without any problems.

Is it bug, or am I not understanding something?

[Phil Harvey]

There is no standard for EXIF in video files, and there are many different ways it can be stored.  ExifTool is able to read most of it, but only able to write some of it.  Canon specifically writes metadata to the thumbnailimage.  I think you may be able to write this by extracting the thumbnail, editing it, then writing it back again.

In case it matters, most other software won't even know this metadata exists.

- Phil

[conr]

Wow, thanks for really quick answer.

I found workaround with hex editing, so I just shared my experience in the case it is important, as behavior was unexpected to me.

Also thanks for providing explanation and better workaround. And above all thx for ExifTool.