Dolby Laboratories P/N 91659 manual Surround Channel Processing, Dynamic Range Compression

DolbyRemote Installation and Operation Dolby Digital Parameters

4.2.2Surround Channel Processing

90 Degree Phase Shift

90 Degree Phase Shift controls whether or not a 90-degree phase shift is applied to the surround channel(s) before the Dolby Digital encoding process. Its use enables decoders to create a Dolby Surround compatible two-channel downmix. This parameter is disabled if the encoding mode does not include any surround channels. This parameter is not available on the DP567.

3 dB Attenuation

3 dB Attenuation controls whether or not the surround channel(s) are attenuated by 3 dB before the Dolby Digital encoding process. This allows material mixed in a room calibrated film style (left and right surround channels are calibrated –3dB with respect to the front channels) to be converted to video style calibration (all channels are calibrated to the same level) by attenuating the surround channel(s) by 3 dB. This parameter is disabled if the encoding mode does not include any surround channels. This parameter is not available on the DP567.

4.2.3Dynamic Range Compression

Dolby Digital has the ability to transmit full dynamic range audio for some listeners as well as additional information which instructs a decoder on how to reduce the dynamic range for others. For example, some people will want a reduced dynamic range for late night listening, or because they have a smaller replay system. The choice of Compression Characteristic and Dialog Normalization parameters as well as the program material control the generation of this extra data.

Compression Characteristic

Compression Characteristic selectsthe compression characteristic that will be applied to the encoded Dolby Digital bitstream. The encoder includes six dynamic range compression modes that correspond to commonly used compression settings. Any mode can be selected at any time. The compression modes apply only to the encoded signal and are not applicable when the Pass Through mode is active. When in the 1+1 Channel Mode, the selected Dynamic Range Compression applies to both mono channels. The actual compression applied to each channel, in this case, is independent, however they share the same compressor characteristics.

RF Overmodulation Protection

RF Overmodulation Protection controls whether or not the Dolby Digital signal is protected against overmodulation distortion when decoded in RF compression mode and subsequently modulated onto an RF carrier. Typical applications include digital television set-top box systems in which decoded audio and video are combined into a composite RF output signal. Note that this parameter has no effect on Line Out or

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