Dolby® Pro Logic® IIx is an extension of Dolby Pro Logic II matrixing technology that delivers enveloping 6.1 and 7.1 surround sound from both stereo and 5.1 content.

Enables 6.1 and 7.1 playback from all stereo and 5.1 content and sources

Enriches surround envelopment

Enhances spatial depth

Improves directionality

Provides larger listening area "sweet spot"

Incorporates soundfield tailoring for movies, music, and games

Dolby Pro Logic IIx extends the original Dolby Digital Pro Logic II technology, which derives 5.1 surround from stereo programming, to derive 6.1- or 7.1-channel surround from both stereo and 5.1-channel content. Incorporated in an A/V receiver (AVR) or processor, Pro Logic IIx allows the listener to add more surround channels with a convenient and easy-to-use upgrade.

Three listening modes tailor the audio to meet the different needs of movie, music, or game sources. The Music mode features additional user controls to adjust the spread of vocals across the front (particularly useful on stereo content) to create a seamless, wraparound surround effect and to set a deeper or shallower surround soundfield.

Why Dolby

When DVDs with Dolby Digital 5.1 soundtracks were introduced, consumers experienced the thrill of discrete multichannel surround in their homes for the first time. The conventional stereo sound from their other sources paled by comparison, leading to the development of Dolby Pro Logic II to help close the gap.

Dolby Pro Logic IIx builds on Pro Logic II technology to enhance not only stereo content, but Dolby Digital 5.1 content as well, from DVDs to HDTV transmissions. The result is a consistent and more compelling surround experience no matter what source and content the listener selects, and an upgrade path for consumers eager to experience a state-of-the-art surround experience.

All versions of Dolby Pro Logic II are available under license to consumer electronics manufacturers to include in home theater products such as AVRs, home-theater-in-a-box systems (HTIBs), and television sets. The technology is available in a wide choice of DSP and IC solutions that also typically implement a variety of surround options including Dolby Digital 5.1.

Dolby Pro Logic II was a major step forward from first-generation surround decoding. In previous logic decoders, including the original Dolby Pro Logic technology, the control circuit looks at the relative level and phase between the input signals. This information is sent to the variable output matrix stage to adjust VCAs controlling the level of antiphase signals. The antiphase signals cancel the unwanted crosstalk signals, resulting in improved channel separation—this is called a feed-forward design.

All versions of Dolby Pro Logic II look at the same input signals and employ a servo loop to match their levels. These matched audio signals are sent directly to the matrix stages to derive the various output channels. Because the same audio signals that feed the output matrix are themselves used to control the servo loop, it is called a feedback logic design. Incorporating global feedback around the logic steering process improves steering accuracy and dynamic behavior.

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