[Tracker] Can a tracker extractor change the MIME type of a input file?

["Lin, Mengdong" <mengdong lin intel com>]

I wonder whether the a extractor can change the MIME type?

I want to support media types protected by OMA DRM V1. 
There is a encryption wrapper outside the original media content. The wrapper file's MIME type is : 
application/vnd.oma.drm.content
By registering this mime type to "shared-mime-info", I can write a tracker extractor to handle this type of 
file. And the extractor can find the MIME type of the original media content by reading the file header.

Then, is it possible for the extractor to inform tracker the real MIME type? So the DRM-protected media can 
still be sorted by its read media type. 
Eg. For a DRM-protected mp3, it will change the mime type from "application/vnd.oma.drm.content" to 
"audio/mp3". Thus a music player application will find it by letting tracker list all audio files.

I'm asking this question because "shared-mime-info" uses file name suffix and simple string match to register 
a new MIME type, so it cannot find the mime type of the embedded media content.

Thanks and Best Regards
Amanda