ExifTool versions and xmp metadata

[Archive]

[Originally posted by bogdan on 2007-05-19 14:08:33-07]

Hi Phil,

I have jpg file, where (some time ago) I've set:

 -xmp:city="somename" my.jpg

Now I've set xmp:city="newname" (using ExifTool v6.90) and after doing that and executing:

exiftool -a -xmp:all my.jpg

-ExifTool shows both:

City=somename

City=newname

Examining jpg file with some HexViewer, I can see that "somename" was probably set with ExifTool v 6.87 -because I can see that version entry inside file.

Now... I assume new entry (for xmp:city) should replace old one and entering:

exiftool -xmp:city="verynewname" my.jpg

-confirmed that: "newname" was replaced with "verynewname", but "somename" remain there.

I've tried to delete xmp:city entry, but only "verynewname" was deleted. Any idea?

Bogdan

[Archive]

[Originally posted by exiftool on 2007-05-20 11:54:21-07]

Hi Bogdan,

Are you sure that the old City tag is XMP?  ExifTool writes IPTC by
default, so if you used "-City=name" you wrote the IPTC, not the
XMP tag.  Use -g1 -a when extracting information to
see where the tags are stored. (This is
FAQ #3).

- Phil

[Archive]

[Originally posted by bogdan on 2007-05-20 12:36:28-07]

Thanks for response,

Yes, I've tried as you suggested too, and I'm sure both are inside XMP.

I'll send image to you via mail, so you can see two City entries inside XMP:

"Olimje" and "LONDON"

Bogdan

[Archive]

[Originally posted by exiftool on 2007-05-21 11:35:33-07]

Hi Bogdan,

Thanks for the sample.  I had considered this possibility when I wrote
my last response, but I have never seen it happen so I went for the
more obvious solution first.  In your JPEG image, there are two XMP
records.  I have never seen this before, but somehow it has happened.
One record is in the proper place, but the other is inside the EXIF
ApplicationNotes as you would find in a TIFF image, not a JPEG.  I have
done a few tests so far and can't figure out how you could coerce exiftool
into writing the ApplicationNotes in a JPEG image, although apparently
this happened since ExifTool 6.87 signed the XMP written here in your
image.

I have tried using ExifTool 6.87 to do various things like write XMP in
your image and copy all tags from a TIFF image to a JPEG, but so far
I haven't been able to reproduce this.  Give me a bit of time to sort this
one out.

If you can give me any details
about the history of the file, it may be helpful.  (ie. were the tags ever
copied from a TIFF or RAW image?)

Thanks for pointing out this problem.

- Phil

[Archive]

[Originally posted by bogdan on 2007-05-21 17:22:05-07]

I've gone thru history of this file and could repeat this behaviour. And the good news first: I think this isn't ExifTool issue.

Here are some details:

I've written XMP location tags directly into Canon raw (CR2) file with ExifTool -as ExifTool is the only tool I trust for doing that.

After that I've converted CR2 to JPG using Canon's Digital Photo Professional (latest version). While doing that, DPP "copies" XMP tags into resulting JPG file too, which is expected behaviour -except (as it seems), these tags cannot be modified later (no matter what ExifTool version being used).

As you may know, Canon DPP modifies raw files too, by writting various DPP settings into file. But that doesn't affect previously written XMP data inside CR2: I can modify XMP data in raw without problem later (after DPP wrote modify data inside CR2).

So my conlusion: If XMP data exists inside CR2, Canon DPP doesn't know how to write that data properly into converted file.

So,... keep on doing good work :-)

Bogdan

[Archive]

[Originally posted by exiftool on 2007-05-21 20:36:12-07]

Good detective work!  This makes sense.  It doesn't surprise me that
Canon DPP could do this.  I would suggest a bug report to Canon, but
I'm 90% sure that it would result in a response of: "Sorry, we don't support
modified CR2 images".

But since it has happened now, I feel obliged to add the ability to exiftool
to modify and/or delete this misplaced XMP information.  I'll look into this,
and you may find this new feature in an upcoming release.

- Phil

[Archive]

[Originally posted by exiftool on 2007-05-22 13:27:04-07]

I have looked into this in a bit more detail.  I can't add the ability to edit
this misplaced XMP information without resulting in a performance hit
when writing information.  To speed processing, ExifTool does not process
EXIF in a JPEG image when only writing XMP.  Even just adding a check to see
if the XMP exists in the EXIF would slow things down, and would be
unnecessary for any properly formatted JPEG image.

But the good news is that you can use the current exiftool to edit this
information by forcing it to process the EXIF.  This can be done by writing
any EXIF tag.  For instance, you could do something like trying to delete
ISO from IFD1 (it never exists there anyway).  This would cause the EXIF
to be processed, allowing the contained misplaced XMP to be edited.  ie)

Code:

exiftool -xmp:city="newname" -ifd1:iso= my.jpg

- Phil

[Archive]

[Originally posted by bogdan on 2007-05-22 16:31:25-07]

Phil, this is genious.

If I understand you advice correctly, then I can use ifd1:iso as "dummy" tag -just to force ExifTool to do XMP work inside exif section. Of course in this case such XMP tags remain inside exif section, but at least we are able to change their content.

Following your suggestion, I was able to delete complete "old" XMP tags, by using:

exiftool -xmp:all= ifd1:iso= my.jpg

-and add new (correctly written) XMP tags... so nobody can blaim ExifTool doing something wrong :-)

I haven't tried, but I agree there's no point to give a note to Canon -I believe they use answering machines for such complains.

And one more note (if somebody wonder): when DPP converts raw file to tif, such odd things (as with jpg) doesn't happen -must be pure luck.

Have a nice day,

Bogdan

[Archive]

[Originally posted by exiftool on 2007-05-22 17:27:06-07]

Hi Bogdan,

It sounds like you understand what is going on, but just one note:

The CR2->TIFF conversion doesn't suffer from the same quirks because CR2
is a TIFF-based format and all of the meta information is stored in the same
locations in both files.  It's only the JPEG which is different:  With JPEG the XMP
and the IPTC are both split off from the EXIF/TIFF information and stored in
separate JPEG segments.

- Phil