What is the difference between Dolby Pro Logic II and Dolby Digital?


Dolby Digital is a lossy data compression method. It must be decoded back into “normal” PCM or Pulse Code Modulated audio on playback. Dolby Digital is used for DVD-Video, settop boxes, and DTV. It cannot be used without a Dolby Digital decoder. If it is not decoded, it will play the AC-3 data as unrecognizable “noise” which, if the playback gain is turned up, could blow your speakers or ears!

In comparison to Dolby Digital, Dolby Pro Logic II is a “matrix” encoder that uses only analog processes, like phase shift and filtering, to conceal the surround information within the stereo audio. Although not discrete like Dolby Digital, Dolby Pro Logic II-encoded audio can be played on any stereo system. If there is a Pro Logic II decoder, it will "unfold" the hidden surround out of the stereo signal and provide Dolby Surround.

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