const char * vortex_frame_get_content_type ( VortexFrame frame  ) 

Returns frame content type.

Return actual frame's content type. The function always return a content type, either because it is defined or because default value is provided ("application/octet-stream").

frame The frame where the content type will be returned.
The content type or NULL if the function fail (because the frame received is NULL or because the frame do not contains a MIME message).