D1 used a 19mm (3/4") tape loaded into cassettes as its media. Component video was encoded as YUV 4:2:2 with PCM audio tracks as well as timecode.
D1 was notoriously expensive and the equipment required very large infrastructure changes in facilities which upgraded to this format. Early D1 operations were plagued with difficulties, though the format quickly stabilized and was reknowned for its superlative image quality.
D1 is still in some usage as of 2003, and many of the technologies introduced with this format are still common to more recent digital videotape formats.