Gets a MediaEncrypter for the media in the input stream.
This method will read from the provided InputStream in order to determine the file type, and then
reset the marked InputStream back to the original read position when finished.
Parameters:
mediaContent - An input stream containing the media content. The InputStream implementation must
support the mark method (for example, mediaContent.markSupported() == true). A BufferedInputStream supports marking.
Returns:
A MediaEncrypter for the media in the input stream.
Throws:
IOException - if an error occurs reading the content.