Dolby Pro Logic was introduced shortly after for playback of the center channel as well. Pro Logic II added left and right surround channels (5.1), and Pro Logic IIx added support for 6.1 and 7.1 ...

it can provide powerful sound with surround sound decoders including Dolby Pro Logic II, Dolby Digital, Dolby Vision, Dolby Dual Mono, DTS 96/24, DTS decoder, Dolby TrueHD and dts HD Enhanced ...