The first digital audio laserdiscs I bought were in/around 1986. They used AC-3 encoding (later known as Dolby Digital 5.1) but were recorded as an RF signal on

The first digital audio laserdiscs I bought were in/around 1986. They used AC-3 encoding (later known as Dolby Digital 5.1) but were recorded as an RF signal onto the discs, because the format was analog. You needed a decoder to turn it into discrete channels, which a few receivers had. But most often you would get an external box, like the Yamaha DDP-1