Only write to specific tag id

[alexmerkel]

I want to write a description to a QuickTime file.
The QuickTime ItemList contains multiple tags named Description but with different ids: 'desc', 'dscp' and '©des'.
When using exiftool -ItemList:Description={} out.mp4, the description is written to both 'desc' and '©des'.

Is there a way to specify, that I only want the information to be written to one tag id, in this case 'desc'?

Thanks,
Alex

[Phil Harvey]

Hi Alex,

This is a bit of a mess. [Video metadata I mean]

'dscp' and 'desc' are avoided when writing, which means that they won't be created but will be updated if they already exist.

'©des' is preferred, so will be created.

To change this, you can override the Quicktime::ItemList tags with user-defined tags using this config file:

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%Image::ExifTool::UserDefined = (
    'Image::ExifTool::QuickTime::ItemList' => {
        "\xa9des" => { Name => 'Description', Avoid => 1 },
        dscp => { Name => 'Description', Avoid => 1 },
        desc => { Name => 'Description' },
    },
);
1; #end

With this config file 'desc' will be created instead of '©des'.

Alternatively, you could change the names of the tags to make them different if you want to address them separately.

- Phil

[alexmerkel]

Hi Phil,

works like a charm 

Thanks a lot,
Alex

[dae65]

In addition to Name and Avoid, some tags as defined in %Image::ExifTool::QuickTime::ItemList have other keys: Groups, ValueConv, PrintConv, etc. Do we need to copy and paste those additional key-value pairs into %Image::ExifTool::UserDefined{...} as well?

I was wondering if ExifTool takes default values from %Image::ExifTool::QuickTime::ItemList into account when just Name or Avoid is overriden in %Image::ExifTool::UserDefined? I couldn't tell from reading ExifTool::TagLookup::AddTags() how it would handle those.

Thanks.

[Phil Harvey]

In addition to Name and Avoid, some tags as defined in %Image::ExifTool::QuickTime::ItemList have other keys: Groups, ValueConv, PrintConv, etc. Do we need to copy and paste those additional key-value pairs into %Image::ExifTool::UserDefined{...} as well?

Yes.  You are overriding the tag definition, and need to include everything that you want for the new tag.

Some defaults may be specified in the table definition (like AVOID).  For ItemList tags, these defaults are:

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    WRITABLE => 1,
    FORMAT => 'string',
    GROUPS => { 1 => 'ItemList', 2 => 'Audio' },

- Phil

[Phil Harvey]

ExifTool 12.03 allows the tag ID to be specified as a family 7 group name, providing a better solution to this problem.  (No user-defined tags are necessary.)

ie) you would use ItemList:ID-a9des:Description, ItemList:ID-dscp:Description or ItemList:ID-desc:Description to access the specific Description tag that you want to read or write.

- Phil

[Kirill Vercetti]

ExifTool 12.03 allows the tag ID to be specified as a family 7 group name

Good day. What if I want to specify both the ID and the language?

This syntax doesn't work:

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-ItemList:ID-desc:Description-ru="Описание на русском"

[Phil Harvey]

Hi Kirill,

Very good point.  The language code was messing with the tag ID match.  I'll fix this in version 12.51.

- Phil