At the heart of the receiver is the surround-sound processor. The most basic surround processors use a Dolby Pro Logic II decoder. Pro Logic II is a "matrix" system that takes an encoded two-channel stereo signal and converts it to a five-channel full bandwidth (range) playback (Left/Center/Right/Left Surround/Right Surround),resulting in a surround experience. Most TV shows are encoded in Dolby Pro Logic II, as are the majority of VHS videos. You can also play DVDs through a Pro Logic II only-receiver because DVD players can synthesize a Pro Logic II signal that mimics a surround soundtrack. The newer Dolby Pro Logic IIx adds the ability of converting stereo or 5.1-channel surround sound for seamless 6.1 or 7.1 playback.