2 apparent bugs in NTFS metadata: comments & search

Hi DO team,

There seems to be 2 problems related to standard metadata:

  • ADS comments are stored in and can be reread from GIF and ICO files but are not shown in the Comments column.
  • Advanced search ignores Comments for GIF, ICO & PNG files but JPG, PSD, EXE, TXT are not affected. Haven't tested it with other file types.

I've also tested the other 2 fields - Rating and Tags - w.r.t Comments column and advanced search, they don't have these bugs.

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The column you want is General > User Description, which should show everything.

Documents > Comment only gets comments saved into certain file formats or which can be returned by one of the shell extensions installed on the system for a given format. (It's mainly for things like Office documents, but the API is extensible so it can pick things up for other formats as well.)

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Leo, thanks for the hint about "User Description". I see how the column works and search works, more or less, too. This will help me a lot.

But... at the moment I'm quite confused why "Comments" field updates sometimes only the ADS, sometimes the container-specific data (like MP3 ID3 or JPG EXIF) and sometimes not, depending on whether a single file is selected or multiple files are selected. Then there's the question why the file modification date is updated even if only ADS is updated but not the file content (e.g. in the case of PNGs).

It looks to me like DOpus tries to hide implementation details of one unified comments field for multiple formats, and behaves quite differently depending on the file format.

Leo, I did some local testing and I'm quite concerned about how DOpus behaves, but maybe you can shed some light to these questions:

  • What exactly is updated when I change "Comments" field via Metadata pane? The format-specific data like EXIF, ID3, etc. or only ADS? Or mixed depending on file type? What is the rule?

  • Is there a difference to what DOpus does if I select a single file type or multiple types, e.g. 1 MP3 + 1 GIF vs 2 MP3s or 2 GIFs?

  • What is the logic behind updating "last modification timestamp"? This looks very, very inconsistent to me, especially with selecting multiple files of one single file type vs multiple files of mixed types. What's the rule? If I select multiple file types, DOpus updates ID3 of MP3 and updates lastmod date of MP3, but why does DOpus update last modification date for PNGs even if only ADS is updated but no PNG-internal data is updated, and why DOpus does not update lastmod for GIF files?

Looking forward to some clarifications.

Where comments are stored depends on the file format, and if Opus knows a way to store them in the main file data itself, or has to store them as NTFS ADS metadata.

Consider a plain text file. There's no way to store a comment in the file itself (without changing what you'd see in a text editor). So it has to go into NTFS ADS. But with a JPEG, there's a comment field in the EXIF block which can be used.

If you select mulitple types the same thing happens as if you did each file individually.

It's up to you when/whether the timestamps are updated when setting comments and other metadata. Preferences / File Operations / Metadata. Some people want them to be updated so software knows to sync or re-read the changes. Some people want the original timestamps to be preserved. You can have whichever you think makes sense.

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Oh, that's a great tip, "Preferences / File Operations / Metadata" that is. The "inside files" was checked in my settings, and ADS was unchecked.

One last question, what does DOpus store in PNG files? If I enter a very long comment in a single PNG file, the file size seems to grow. But PNGs don't have any EXIF, ID3... type of metadata to my knowledge, neither DOpus shows it in Picture Viewer, nor IrfanView or Photoshop 20 shows any extra information.

The PNG format supports EXIF, although there are a few competing standards.

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Ok. So DOpus is ahead of the curve, IrfanView & Photoshop. Good stuff! (y)

Thanks for the clarifications and your patience!
Have a good one, cheers!