change date/time only working absolut

[miner1]

Hey,
(using the latest version of IMATCH), today I tried to change the exif date/time of several mp4-files, RELATIV of -12 hours. This didn´t worked. Setting the date/time ABSOLUTE it works.
What am I doing wrong?

Glückauf
Gero

[Mario]

I did't even know that MP4 files may contain an EXIF record. EXIF is only designed for still camera files...
And ExifTool does not update video files as far a I know.

Was there already a date in the file before?
Any error messages from ExifTool in the output panel when you try to set a relative date?
You can open the ExifTool output panel via View menu > Panels and see if ExifTool reports warnings or errors when updating the video file.
I recommend using the XMP date and time metadata only (via the Metadata Panel).

See also: How IMatch uses Date and Time Information

[miner1]

Hey Mario, thanks for your replay

yes the old date/time is/ was 01.01.2013 22:53:56

Attached you find the ExifTool Output
- First I used -12 hours on this file (relativ) 
- Secound I set it to 01.01.2013 10:53:56 (absolut)   

Unfortunately there are about 100 mp4-files I have to adjust (relativly)

Glückauf
Gero

[Mario]

ExifTool does not update the video file, only the XMP data.
The relative date and time commands look OK. If this fails it's because you are trying it for a video files. This only works for image files containing EXIF data and for files which ExifTool can actually write to. I'm quite sure Apple video files don't have image EXIF records.

[ben]

I came across a similar problem the other day.
The change date time window is of great help to me. Also changing dates by a relative amount is extremely helpful.

Maybe we should file a feature request. So it not only changes the exif date but also xmp data. So video files get changed as well.

Once again, this I a very helpful function in iMatch.

[Mario]

It changes both the EXIF and XMP metadata.

But, when re-importing metadata after the modification, existing (and not updated) date information in the video file may override XMP data. IMatch looks for certain known date fields in video files to fill XMP and the "File DateTime" standard attribute. There is no synchronization between proprietary date and time information in video files and XMP metadata.

This is not a problem for IMatch if you use it in the normal way (setting the date and time in the Metadata Panel).
But if you use the Modify EXIF Date and Time features only designed for image files with EXIF metadata, the results may not be what you expect.

Probably a modify absolute/relative feature based on XMP data (e.g. as an option for Metadata Panel date and time field) would be more useful in this context. That would be a FR I think...