Does anyone know the origin / usage of the 0xea1c padding tag?

[viziio504]

I'm doing some data analysis and finding: 59932 (0xea1c, defined as "padding") as an EXIF tag in some JPEG images. Looking it up, I see this same tag exists in the wild in numerous places. But none of these instances explain or mention the tag specifically:

• Instance 1: https://github.com/alicevision/meshroom/issues/601
• Instance 2: https://buildmedia.readthedocs.org/media/pdf/exif/latest/exif.pdf
• Instance 3: https://exif.readthedocs.io/en/latest/usage.html
• Instance 4: http://watfordindianassociation.org.uk/index.php?option=com_hwdphotoshare&task=exif&photo_id=78&Itemid=222
  

It exists in this documentation of tags: https://exiftool.org/TagNames/EXIF.html as padding, but I have not found any explanation for why there would be padding as a meta tag, or in what scenario it would ever be used, since it does seem to be used.

it's used all over the place (mostly in older image files, but not exclusively). But I need to know what causes it and can't find a single reference to a purpose for using it, or an explanation of why anyone has used it. It's a non-standard tag, yet it's listed in documentation as padding, so some org / popular application must've defined it that way.

[StarGeek]

If you refer to page 18 of the XMPSpecificationPart1.pdf, it lists the following

When XMP is embedded within digital files, including white-space padding is sometimes helpful. Doing so facilitates modification of the XMP packet in-place. The rest of the file is unaffected, which could eliminate a need to rewrite the entire file if the XMP changes in size. Appropriate padding is SPACE characters placed anywhere white space is allowed by the general XML syntax and XMP serialization rules, with a linefeed (U+000A) every 100 characters or so to improve human display. The amount of padding is workflow-dependent; around 2000 bytes is often a reasonable amount.

I think the basic idea is the same no matter what group it's found in.

[Phil Harvey]

Microsoft likes to add this Padding.  It can make it faster to update the file metadata if your software is optimized for this.

- Phil