3gp mime support

[m_uysl]

Some devices using 3gp format for wp mobile app.

[georgestephanis]

Looks like some phones upload 3gpp videos as .mp4 files? As it's an extension of mp4, would we need some other testing to catch that?

[m_uysl]

Replying to georgestephanis:

Looks like some phones upload 3gpp videos as .mp4 files? As it's an extension of mp4, would we need some other testing to catch that?

No, They are using 3gp and try to upload 3gp but mime not defined in core. People can add 3gp mime support but it should be in the core. (my thought)

[azaozz]

Seems 3gp, 3g2 and 3gpp are fairly popular. For example KitKat (Android 4.4) tries to upload a "recording-*.3gpp" file when the user selects "Sound Recording" as the upload source.

The proper mime types seems to be video/3gpp and video/3gpp2 despite that the files can contain only audio. Both ​RFC 3839 and ​RFC 4393 state that:

The type "audio/3gpp" may be used for files containing audio but no
visual presentation (neither video nor timed text, for example).
...
The type "video/3gpp" is valid for all files. It is valid to serve
an audio-only file as "video/3gpp".

[wonderboymusic]

In 28841:

Add mime support for 3gp, 3g2 and 3gpp video formats. These are not supported by MediaElement or the WP media shortcodes, just an FYI.

Props azaozz, m_uysl.
Fixes #23380.