Font MIME type does not match extension

[gonzalo_diaz]

Hello,

I am editing an ebook in epub format, which contains an embedded font (Noto Nastaliq Urdu https://fonts.google.com/noto/specim...+Nastaliq+Urdu)

When importing the ebook into Calibre, then using "Edit", and the the useful "Check Book" utility, I get the following warning:

"The file OEBPS/Fonts/NotoNastaliqUrdu_VariableFont_whgt.ttf has a MIME type that does not match its extension"

What does that error mean, and how can I correct it?

I saw some related comments here:
https://bugs.launchpad.net/calibre/+bug/2023646
but I don't understand what to do.

Any comment, please?
The book seems to work well, but I am curious about that error.

[theducks]

The right side of the debugger offer solutions for many SELECTED error messages. Select the error on the left: pick the solution on the right
Personally, I avoid Fix All until I have reviewed and corrected ones like you saw.
Most common Fix all is bad ID, usually the last FIX I do

[nabsltd]

Originally Posted by gonzalo_diaz

What does that error mean, and how can I correct it?

My guess is that the mime type for the font in the manifest is "font/otf", which means an OpenType font, while Check Book expects that a .ttf extension would require a mime type of "font/ttf", meaning a TrueType font. It's an exceedingly minor nitpick and won't make any difference, because OpenType is pretty much a proper superset of TrueType, and the same rendering engine is used for both in every implementation.

I've seen fonts from commercial foundries where the file extension doesn't match the actual contents, and it goes both ways (TrueType in a .otf and OpenType in a .ttf).

Changing the extension to .otf and setting the mime type to "font/otf" wouldn't hurt anything, even if the font really is a TrueType font, and it should fix your error.

[JSWolf]

The calibre error checker will notice that the mine type is incorrect for the font and allow you to auto-fix it. Done!