For broadcasters with stereo infrastructures that transmit Dolby® 5.1 on their main HD services, Dolby Pro Logic® II is the best way to derive high-quality stereo audio from the 5.1 master.
Delivers compelling surround-encoded audio, compatible with mono, stereo, and all generations of Dolby Pro Logic surround playback (including Dolby Pro Logic IIz)
Complements the discrete 5.1 audio on the primary HD services
Offers encoding tools to create matrix-encoded stereo from discrete 5.1-channel content for broadcast program preparation
Dolby Pro Logic II encoding transforms two-channel audio into surround sound for listeners with Pro Logic audio systems and televisions.
During program production, a Dolby Pro Logic II encoder combines as many as five input signals—Left, Center, Right, Left Surround, and Right Surround—into a matrix-encoded, two-channel Left total/Right total (Lt/Rt) signal. The encoded signal is thereafter treated as conventional two-channel stereo audio throughout the broadcast distribution chain.
Broadcast solutions for Dolby Pro Logic II include the Minnetonka SurCode™ for Dolby Pro Logic II Encoder and Decoder, the DP563 Dolby Surround and Pro Logic II Encoder, and the Dolby DP568 Professional Reference Decoder.
Dolby Pro Logic II matrix encoding was developed to allow a listening experience closer to that provided by the discrete Dolby Digital 5.1-channel format used for DVDs, digital cable, HDTV and DTV, satellite, and the most sophisticated video games. Pro Logic II delivers five full-range channels, including two surround channels, matrix-encoded onto an otherwise standard (and compatible) stereo transmission.
Critical to Dolby Pro Logic II is its decoder design. 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.
Dolby Pro Logic II looks at the same input signals and employs 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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