media
The media type produced by this converter (to use as content-type header).
If the media type contains a charset parameter and it is different from UTF-8, frames are encoded to bytes using the given charset, and sent as binary web socket frames (because text frames can only be UTF-8). If no charset is specified, or if it is specified as UTF-8, then text web socket frames are sent, which means they will be encoded as UTF-8.