[theora-dev] File extensions

David Wheeler dwheeler at ida.org
Mon Jan 13 06:22:38 PST 2003

Sylvia Pfeiffer said:

<p>> Now, leading on from here to file extensions is a different issue. I
> would recommend to have different file extensions for each of the
> defined Ogg media mappings ogg-theora, ogg-vorbis and ogg-speex. My
> reasoning is that it makes it easier for programs to map from the file
> extension to the MIME type and from there to the application to use
> without having to look inside the file. My check of MIME types also
> found that mostly a MIME type maps to many file extensions, but one file
> extension belongs mostly to one MIME type only.

<p>Note that the MIME registration procecedures request that a file
extension be defined also for each MIME type.  You're quite right -
a given file extension should map to one MIME type, since that way
file managers, web servers, etc. can quickly determine what the MIME type
is and/or what helper program to run.

Note that there are still advantages to defining a three-character
file extension (!).  3-character extensions are slightly constraining,
but they are far more portable.  In particular, CD-ROMs are typically
burned using a format based on MS-DOS (3-character only extensions), plus
an operating-system-specific extension that isn't understood by everyone
(Joliet = Windows, Rock River = Unix/Linux, Mac = MacOS).

Thus, if you want users to be able to easily burn a CD from any system,
and have it play correctly on any player (particularly embedded systems
that only understand the MS-DOS catalog), you'd better have a 3-character
extension that gives enough information on what helper application to run.

Thankfully, ".ogX" (where X is variable) doesn't seem to be widely used,
so there's lots of room for the common formats.

<p>--- David A. Wheeler
     dwheeler at ida.org

<p>--- >8 ----
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