O3A Decoder - 3D7.1

O3A Decoder - 3D7.1

Host Support

Host TypeSupport
AAXYes, output mapped to 7.1 stem
VST2Yes

Audio

ChannelsContent
Input16O3A
Output83D7.1 Surround (mapped to standard 7.1)

Controls

Description

This plugin takes a third order ambisonics (O3A) mix and decodes it as a 3D7.1 surround mix.

3D7.1 is a modified version of the 7.1 speaker layout invented by Simon N. Goodwin. It is based on the equipment used for 7.1 but places the speakers in different locations, some being raised or lowered.

If you intend to use this decoder then you should move your speakers to these new locations. Alternatively there is a normal O3A decoder for 7.1.

Channel Ordering for AAX

For AAX, the channel ordering and assumed speaker locations for the 3D7.1 surround mix are as follow.

Channel7.1 Speaker Position3D7.1 Speaker PositionAzimuthElevationUsed in 5.1
1Front LeftFront Left High+51+24Yes
2Front CentreFront Centre00Yes
3Front RightFront Right High-51+24Yes
4Left Surround SideRear Left Low+129-24Yes
5Right Surround SideRear Right Low-129-24Yes
6Left Surround RearRear Centre High+180+55No
7Right Surround RearFront Centre Low0-55No
8LFELFE--Yes

VST

For VST, the channel ordering and assumed speaker locations for the 3D7.1 surround mix are as follow.

Channel7.1 Speaker Position3D7.1 Speaker PositionAzimuthElevationUsed in 5.1
1Front LeftFront Left High+51+24Yes
2Front RightFront Right High-51+24Yes
3Front CentreFront Centre00Yes
4LFELFE--Yes
5Rear LeftRear Centre High+180+55No
6Rear RightFront Centre Low0-55No
7Side LeftRear Left Low+129-24Yes
8Side RightRear Right Low-129-24Yes

In the tables above, azimuth is measured anticlockwise (left) from the front and elevation upwards from the horizontal.

The plugin is available in the O3A Decoding plugin library.

Controls

Control: Method

Three methods are supported, "Basic", "Reconstruction" and "Tinted Reconstruction". Generally, "Basic" is recommended except where the speaker rig to be used for playback is known and has been set up accurately.

MethodDescription
BasicThis method produces a resilient decoding which should play well on a range of speaker systems including large venues.
ReconstructionThis method controls the soundfield at the centre of the listening space to produce a clearer spatial image. It relies on the speaker layout being set up accurately.
Tinted ReconstructionThis variant of the Reconstruction method performs HRTF-based tinting on the audio stream to strengthen the spatial image. Again, it relies on the speaker layout being set up accurately.

Control: LFE Crossover

This determines if any audio is sent to the LFE channel. It may be set to "Off" and this is recommended. If enabled, audio is extracted from the main mix into the LFE channel using the indicated crossover frequency (between 1 and 200Hz).

Control: LFE Gain

If the LFE gain is active, this gain is applied to it. Some export formats may need this set to -10dB to take into account a +10dB gain applied during playback.