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Audio Design Associates
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Appendix A:
Multichannel and Two Channel Decoding Modes and Enhancements
Multichannel Encoding Overview
Dolby Digital and Dolby Digital Surround EX
A Dolby Digital bit stream most typically contains a 5.1 channel, or a 3.2.1.0 mix. The 3 refers to the
front three channels (left, center, right), 2 refers to the surround channels (left and right), and the 1 or
“.1” refers to the called LFE - Low Frequency Effects channel. While there are other options for
mixing Dolby Digital (older movies that were never mixed in multi-channel but play off a DVD are
often encoded in Dolby Digital, as 2.0.0.0 or stereo), most material is available in a 5.1 format.
Dolby Digital Surround EX is best described as an enhancement to Dolby Digital. Here a mono signal
is embedded into the discrete surround left and right channels. This signal creates an image in the back
of the room, between the surround left and right channels. If a film has been encoded in Dolby Digital
Surround EX, the digital bit stream will contain a “flag” which tells the Suite 7.1that it has been
specifically mixed and mastered to take into consideration a playback system that has one or two
surround back speakers.
DTS 5.1 Surround
Source material encoded in DTS 5.1 Surround operate in a manner similar to Dolby Digital 5.1 Surround
material. When playing software encoded in DTS 5.1 Surround, and selecting an EX/ES mode will
send audio to the back surround speakers. This feature performs similar to the EX feature for Dolby
Digital 5.1 tracks. Also, like Dolby Digital 5.1 material, selecting a THX or THX Ultra 2 mode will
engage the appropriate THX enhancements.
DTS ES Matrix
Much like Dolby Digital Surround EX, DTS ES Matrix encoded material contains the ES flag in the
digital bit stream, indicating that this track was specifically mixed on a system with back surround
speakers. The number of Output channels is not effected by the ES flag unless and EX/ES or THX
Ultra 2 mode is selected. Then the BSL and BSR output channel play back audio from the back
surround speakers. All cinema modes as described above are also available with a DTS/ES bitstream.
DTS ES Discrete
A disc containing a DTS ES Discrete audio track is unlike the other 5.1 or 5.1 with EX/ES encoding
formats. DTS ES Discrete material has a sixth fully discrete channel in addition to LFE. The DTS ES
discrete decoding process is currently the only source material capable of providing a full seven-channel
bitstream in addition to the LFE channel for true 7.1 decoding. When playing a DTS ES Discrete
audio track, the Suite 7.1 will automatically detect the ES Discrete flag in the digital bit stream. All
cinema modes as described above are also available with a DTS/ES Discrete bitstream.
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