Both are decoding systems for home theater sound. Dolby Digital is the successor to Dolby Pro-Logic. Pro-Logic is the more common of the two systems and is found on video tapes, laser disks, even DVDs. Pro-Logic is actually four channels of sound that is reproduced through five speakers. The four channels are: left, center, right and surround channels. The surround channel consists of two speakers, and in Pro-Logic the same sound comes from both speakers. Pro-Logic is typically an analog system. Dolby Digital is a discrete digital system offering six separate channels of sound with a dedicated subwoofer channel for deep bass. The six channels are: left, center, right, left surround, right surround and LFE (low frequency effect) for bass. DD is known as 5.1 channel sound. Dolby Digital has been declared the audio standard for DVD and HDTV. Dolby Digital offers greater dynamic range than Pro-Logic, better frequency response and improved separation between channels.
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