From 1991 until 1998, Media Composer 1000, 4000 and 8000 systems were Macintosh-only, and based on the NuVista videoboard by Truevision. The first-release Avids (US) supported 640x480 30i video, at resolutions and compression identified by the prefix "AVR". Single-field resolutions were AVR 1 through 9s; interlaced (finishing) resolutions were initially AVR 21–23, with the later improvements of AVR 24 through 27, and the later AVR 70 through 77. AVR12 was a two-field interlaced offline resolution. Additionally, Avid marketed the Media Composer 400 and 800 as offline-only editors. These systems exclusively used external fast SCSI drives (interfaced through a SCSI accelerator board) for media storage. Avid media was digitised as OMFI (Open Media Framework Interchange) format.