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ExifTool Forum

ExifTool => The "exiftool" Application => Topic started by: Mac2 on November 28, 2014, 12:34:30 PM

Title: Where does File::Comment come from?
Post by: Mac2 on November 28, 2014, 12:34:30 PM
Hi,

I have a JPEG file which contains an EXIF::userComment (user comment), and also IPTC:caption (IPTC caption). But exiftool -G1 -all:all also lists a

[File]  Comment : Embedded comment (File Comment)

where does this data come from? It's not EXIF, not IPTC, not XP, not XMP and I could not find any documentation on the File group (the File group is mentioned in tag groups but not in tag names).

Title: Re: Where does File::Comment come from?
Post by: Phil Harvey on November 28, 2014, 12:42:39 PM
The file group is specific to the format of file being read.  In JPEG files, it is a JPEG Comment (the "COM" JPEG segment).  In GIF files, it is a GIF Comment.  But just to be inconsistent, in a PNG file it is reported as PNG:Comment.

It is separate from EXIF, IPTC and XMP.

- Phil
Title: Re: Where does File::Comment come from?
Post by: Mac2 on November 29, 2014, 07:50:32 AM
Hi, Phil

thanks for the info (and for fixing the invalid XML output problem!).

So far I thought I could skip the [File] group completely when importing data from ExifTool. I was under the impression that most of the tags are just dupes of info I gather elsewhere anyway. Now it seems that I need to import at least the comment from that group. Or not, because only one user ever complained about this tag...
Title: Re: Where does File::Comment come from?
Post by: Phil Harvey on November 29, 2014, 08:07:16 AM
I would have thought that ImageWidth and ImageHeight were important to most people...

- Phil
Title: Re: Where does File::Comment come from?
Post by: Mac2 on November 29, 2014, 01:26:30 PM
Sure. But my application imports images, videos and other files as it's main task, I have the info about the file name, size, last modified timestamp, dimensions etc. already. This is why I could skip [File] so far.
Title: Re: Where does File::Comment come from?
Post by: Phil Harvey on November 29, 2014, 02:38:06 PM
Got it.

- Phil
Title: Re: Where does File::Comment come from?
Post by: Mac2 on November 30, 2014, 10:51:24 AM
Is there a list of the tags in the [File] group? The group is not listed on the standard "tag group" page.
Title: Re: Where does File::Comment come from?
Post by: Phil Harvey on November 30, 2014, 05:44:57 PM
These are found in the Extra tags documentation (https://exiftool.org/TagNames/Extra.html).

Note that the System tags are also in the family 0 "File" group.

- Phil
Title: Re: Where does File::Comment come from?
Post by: Mac2 on December 01, 2014, 04:49:14 AM
Very good. I played with this a bit and the embedded JPEG comment tag shows up in the Extra::Comment tag, but only when I no longer add the --file:all when importing data.

The [File] group seems to be required in order to fill (at least some) of the [Extra] tags? So far I only imported Extra::Warning and Extra::Error, which are filled even if [File] is excluded. I have now removed the --file:all in my import ARGS file and added the Comment to the list of Extra tags my software does not skip when copying into the database. Now the Extra::Comment is filled.
Title: Re: Where does File::Comment come from?
Post by: Phil Harvey on December 01, 2014, 10:27:15 AM
I think there is some confusion.

There is no "Extra" group.  The Extra table lists a collection of tags from other groups.  The specific groups that they belong to are listed in the table.

- Phil
Title: Re: Where does File::Comment come from?
Post by: Mac2 on December 01, 2014, 01:04:08 PM
Sorry, mix of terms. Extra table. File group. Got it.
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