Simple Explanation

An older surround-sound format that creates simulated surround channels from regular stereo audio (2 channels).

Concise Technical Definition

A matrixed surround sound system that extracts additional audio channels—such as center and surround—from a standard stereo signal using phase and amplitude cues.

Layman-Friendly Analogy

Like turning a flat 2D photo into something that “feels” 3D—Pro Logic takes stereo sound and adds the illusion of surround.

Industry Usage Summary

Common in VHS, LaserDisc, and early DVD systems, Dolby Pro Logic was a key step toward surround sound, especially before discrete formats like Dolby Digital became standard. Still supported by many AVRs for compatibility with stereo sources.

Engineering Shortcut

Matrix decoding of surround channels from 2-channel stereo; legacy format.

Full Technical Explanation

Dolby Pro Logic is a surround-sound decoding technology developed by Dolby Laboratories that uses matrix encoding to extract four channels—Left, Center, Right, and a mono Surround—from a stereo (2-channel) source. It relies on phase differences and amplitude cues encoded during mixing. Unlike discrete formats (e.g., Dolby Digital), Pro Logic synthesizes the surround experience from limited data. It was widely used in analog formats like VHS and early DVDs. Variants like Pro Logic II and IIx later added full-range stereo surround channels and improved fidelity. While mostly obsolete in modern setups, Pro Logic remains useful for upmixing stereo content.