Similar to Virtual Dolby Digital, Virtual Dolby Surround is another way to use the Dolby Digital bit stream from a DVD-ROM. The first step is for the Dolby Digital decoder to down mix the 5.1 channels into a Dolby Surround encoded two-channel format. The center channel is provided by a “phantom” mode. And the mono surround channel is further processed by additional DSP circuitry and turned into “virtual” surround.