The Advanced Television Systems Committee, Inc., is an international, non-profit organization developing voluntary standards for digital television. Specifically, ATSC is working to coordinate television standards among different communications media focusing on digital television, interactive systems, and broadband multimedia communications. ATSC Digital TV Standards include digital high definition television (HDTV), standard definition television (SDTV), data broadcasting, multichannel surround-sound audio, and satellite direct-to-home broadcasting.
http://www.atsc.org/aboutatsc.html