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The US ATSC HDTV system originally specified two different kinds of closed captioning datastream standards—the original (available by Line 21) and another more modern version encoded in MPEG-2, the CEA-708 standard. The US FCC mandates that broadcasters deliver (and generate, if necessary) both datastream formats. The Canadian CRTC has not mandated that broadcasters either broadcast both datastream formats or exclusively in one format.