HD downconverter (high-definition downconverter). An HD (high-definition) downconverter is a device that converts high-definition television (HDTV) video to standard-definition video that can be viewed on conventional television (TV) receivers or computer monitors, or recorded on DVD. A high-end HD downconverter performs these functions with a minimum of blurring, aliasing, and conversion noise, and can provide output at a variety of refresh rate's and aspect ratios. HDTV is a digital television display technology that provides image quality similar to that of 35-mm movies, and sound quality similar to that of a digital audio compact disc (CD). HD resolution is 720 or 1080 lines per frame, while standard resolution is 480 lines per frame. DVD is an optical disc technology with a multi-gigabyte (GB) storage capacity on a disc that is the same size as a CD of the type used for audio reproduction and computer storage. HDTV broadcasters have expressed interest in HD downconverters, because they facilitate the conversion of HD programming to standard format for simulcasting to subscribers who might not own HDTV receivers. HD downconverters can also be used to simulcast HDTV programming over the Internet for viewing on personal computers. Video production engineers can use HD downconverters to record HDTV programs on DVD. Some companies describe their products as HD-SDI (Serial Digital Interface) downconverters. Also See: HD upconverter, a device that converts the digital data on a DVD to a format that can be viewed directly on an HDTV receiver without intermediate conversion to an analog signal