Bug 2692

There are some particular bugs caused by the fact, that IANA has registered MIME
types, which are used de-facto as a "container" MIME type, as image/, audio/ or
video/, however container MIME types should be application/ of multipart/.

It causes problems to RFC compliant applications, which consider suffix and
contents MIME types in conflict, if both MIME types are image/, audio/ or video/.

For more see discussion in bug 1608 and
http://bugzilla.gnome.org/show_bug.cgi?id=138033

This proposal says:

If heuristic used in shared-mime-info can detect only data envelope, we should
use non-standard application/x-type instead of standard but problematic image/,
audio/, video/, official MIME types.

Example:

image/tiff: If heuristics will detect only TIFF file format container, it should
return application/x-tiff. Only if there will be a heuristics, which can
guarantee, that data inside is a regular TIFF image (and not EXIF or camera RAW
file), such heuristics can use image/tiff.

There is an incomplete list of affected MIME types:

- image/tiff (can be exif, digital camera raw)
- something needs to be done with text/xml and text/sgml (can be html, svg)
- video/quicktime (can be e. g. audio/3gpp) and other A/V container data types
- maybe for compressed files, where compression can be considered as a type of
container, consider also ZIP or gzip as container