Globally , large media conglomerates include Bertelsmann ( BMG ) , National Amusements ( Viacom Inc. and CBS Corporation ) , Sony Corporation , Comcast , The Walt Disney Company , AT & T Inc. , Fox Corporation , Hearst Communications , MGM Holdings Inc. , Grupo Globo ( South America ) and Lagardère Group .
Bertelsmann , also known as BMG , is one of the largest media conglomerates in the world .