Surround decoding and surround sound formats

Surround Decoding is the process that AV receivers / AV processors performs to convert a digital or analog audio signal to multichannel audio.

There are currently a number of surround sound formats used to transfer and store multichannel sound. Most of the surround sound formats are supported by all products, but some is only available on the most expensive products or on products from special vendors. This part of the guide goes through the surround sound formats used in today's AV-amplifiers.

Digital surround sound formats
Digital surround sound formats are available from DVD, Blu-Ray, Satellite, digital cable TV, digital terrestrial, game consoles and other digital sources. What characterizes most the digital audio format is that each audio channel is encoded in audio information separately from the other channels. This does not apply Dolby Digital EX 6.1 and DTS ES Matrix where the 6th channel is matrix encoded in the surround channels.

Dolby Atmos is a new Digital format where the audio i encoded with location information instead of being connected to a specific channel. Below is a table of the various digital surround sound systems with information about the number of channels and what sources the surround sound format is avaiable from. If you click on the Surround Sound format name you will find a detailed guide for each format.

Audio system Channels Sources Transfer
Dolby Digital 1.0,2.0, 5.0, 5.1 DVD,Blu-Ray,Xbox 360/One, Playstation 3/4, Streaming (Netflix++) Optical/Coaxial/HDMI
Dolby Digital EX 6.1 DVD Optical/Coaxial/HDMI
DTS 5.1 DVD Optical/Coaxial/HDMI
DTS ES 6.1 DVD Optical/Coaxial/HDMI
Dolby Digital Plus 5.1, 7.1 Blu-Ray, Streaming (Netflix++) Optical/Coaxial/HDMI
Dolby TrueHD 5.1, 7.1 Blu-Ray HDMI 1.3
Dolby Atmos 5.1.4, 7.1.4 Blu-Ray HDMI 2.0
DTS-HD Master Audio 5.1, 7.1 Blu-Ray HDMI 1.3
MPCM 5.1, 7.1 Blu-Ray HDMI 1.1
SACD 5.1 SACD HDMI 1.2a, iLink
DVD Audio 5.1 DVD Audio HDMI 1.1, iLink
MPEG Multichannel 5.1 DVD Optical/Coaxial/HDMI

Analog surround systems
The first sound system that was introduced in the home theater was Dolby Pro Logic. This is the home version of Dolby Surround which was used in the cinema. Dolby Pro Logic is used to recreate surround sound based on a conventional stereo signal. (digital or analog). Dolby Pro Logic have limited frequency response to the rear speakers. Dolby Pro Logic II is an upgrade of this sound system that gives full frequencies stereo in the rear speakers. Both these systems are based on the sound to the rear speakers is matrix encoded into an analog or digital stereo signal. Read all about this in Dolby Pro Logic Guide.

Secondary audio formats
In addition to surround formats used in sources such as DVD and Blu-Ray has been developed formats which makes a second treatment on already decoded audio formats typically create multiple channels based on advanced processing. This is channels that are not defined by the manufacturer of the sound. In this way one can mix audio processing from different vendors. Eg one can take a 5.1 DTS audio tracks to make it into 7.1 using Dolby Pro LogicIIz. Below is a list of such formats and the channel configuration they manage to create using different types of channel configurations.

Surround sound format Channels before processing Channels after processing
Dolby Pro Logic IIx 5.1 7.1
Dolby Pro Logic IIz 5.1 7.1 (5.1 + front høyde)
Dolby Pro Logic IIz 7.1 9.1 (7.1 + front høyde)
DTS neo:X 2.0,5.1 9.1 (5.1 + front bredde/høyde)
DTS neo:X 2.0, 5.1, 7.1 11.1 (7.1 + front bredde/høyde)
DTS neo 6 2.0, 5.1 6.1
Audyssey DSX 5.1 9.1 (5.1 + front bredde)
Audyssey DSX 7.1 11.1 (7.1 + front bredde/høyde)
Yamaha Cinema DSP 7.1 11.1 (7.1 + front/bak presence)