Surround Sound Mode refers to the decoders of multi-channel soundtracks found on DVDs and video cassettes.
\r\nDolby Digital allows from 1 to 6 channels (front right, front left, rear right, rear left, center and subwoofer) of sound be decoded and then passed on to any receiver with 6-channel inputs.
\r\nPro-Logic provides 4 channels (left, right, center, surround). Pro-Logic II encodes 5 channels (left, right, center, left surround, right surround). Pro-Logic technology is widely used as it can be encoded into any form of stereo audio stream, including digital files such as MPEG-1/2, MP3, audio CDs, and VHS.
\r\nDTS Decoding is a little like Dolby Digital. It is a 6-channel digital surround format that provides a separate channel of sound to five speakers (right, center, left, right surround, left surround), and a subwoofer. There are fewer DTS than Dolby Digital recordings today, but popularity seems to be on the rise.