O7A Decoder - Spatial Audio Dome 64

O7A Decoder - Spatial Audio Dome 64

Host Support

Host TypeSupport
AAXYes, output mapped to seventh order ambisonics
VST2Yes

Audio

ChannelsContent
Input64O7A
Output64Feeds for 64 Spatial Audio Objects (mapped to seventh order ambisonics for AAX)

Description

This plugin converts a 3D O7A mix into 64 channels of audio for use in a "Spatial Audio" mix.

When we use the term "Spatial Audio" here, we mean systems like Dolby Atmos or Apple Spatial Audio which represent the audio scene using a fixed multichannel speaker bed and mono audio object located in 3D space. Here, we use a number of these audio objects as a dome of virtual speakers which present the O7A scene.

The plugin user interface shows a visualisation of the dome as seen from above.

Dome 64

Spatial Audio Dome 64 Virtual Speaker Layout

This dome arrangement is designed for use with 64 objects. They need to be set to specific fixed locations:

Spatial Audio Coordinates between -1 and +1

ObjectLeft/Right (Sp. Audio X)Back/Front (Sp. Audio Y)Elevation (Sp. Audio Z)
10.000+1.0000.000
2-0.198+1.0000.349
3+0.198+1.0000.349
4-0.414+1.0000.000
5+0.414+1.0000.000
6-0.673+1.0000.345
7+0.673+1.0000.345
8-0.201+1.0000.831
9+0.201+1.0000.831
10-1.000+1.0000.000
11+1.000+1.0000.000
12-0.647+1.0000.782
13+0.647+1.0000.782
14-1.000+0.6730.345
15+1.000+0.6730.345
16-0.177+0.5791.000
17+0.177+0.5791.000
18-1.000+0.6470.782
19+1.000+0.6470.782
20-0.582+0.5821.000
21+0.582+0.5821.000
22-1.000+0.4140.000
23+1.000+0.4140.000
24-1.000+0.1980.349
25+1.000+0.1980.349
26-0.176+0.1761.000
27+0.176+0.1761.000
28-1.000+0.2010.831
29+1.000+0.2010.831
30-0.579+0.1771.000
31+0.579+0.1771.000
32-1.0000.0000.000
33+1.0000.0000.000
34-0.579-0.1771.000
35+0.579-0.1771.000
36-1.000-0.2010.831
37+1.000-0.2010.831
38-0.176-0.1761.000
39+0.176-0.1761.000
40-1.000-0.1980.349
41+1.000-0.1980.349
42-1.000-0.4140.000
43+1.000-0.4140.000
44-0.582-0.5821.000
45+0.582-0.5821.000
46-1.000-0.6470.782
47+1.000-0.6470.782
48-0.177-0.5791.000
49+0.177-0.5791.000
50-1.000-0.6730.345
51+1.000-0.6730.345
52-0.647-1.0000.782
53+0.647-1.0000.782
54-1.000-1.0000.000
55+1.000-1.0000.000
56-0.201-1.0000.831
57+0.201-1.0000.831
58-0.673-1.0000.345
59+0.673-1.0000.345
60-0.414-1.0000.000
61+0.414-1.0000.000
62-0.198-1.0000.349
63+0.198-1.0000.349
640.000-1.0000.000

It is very easy to make a mistake entering coordinates like these. We recommend setting up a template and checking it carefully before using it for any real projects.

Spatial Audio Coordinates between -100 and +100

Objectl/rf/rheight
101000
2-2010035
32010035
4-411000
5411000
6-6710035
76710035
8-2010083
92010083
10-1001000
111001000
12-6510078
136510078
14-1006735
151006735
16-1858100
171858100
18-1006578
191006578
20-5858100
215858100
22-100410
23100410
24-1002035
251002035
26-1818100
271818100
28-1002083
291002083
30-5818100
315818100
32-10000
3310000
34-58-18100
3558-18100
36-100-2083
37100-2083
38-18-18100
3918-18100
40-100-2035
41100-2035
42-100-410
43100-410
44-58-58100
4558-58100
46-100-6578
47100-6578
48-18-58100
4918-58100
50-100-6735
51100-6735
52-65-10078
5365-10078
54-100-1000
55100-1000
56-20-10083
5720-10083
58-67-10035
5967-10035
60-41-1000
6141-1000
62-20-10035
6320-10035
640-1000

Polar Coordinates

ObjectAzimuthElevation
10.000.00
211.2018.90
3-11.2018.90
422.490.00
5-22.490.00
633.9415.97
7-33.9415.97
811.3739.17
9-11.3739.17
1045.000.00
11-45.000.00
1232.9033.29
13-32.9033.29
1456.0615.97
15-56.0615.97
1617.0058.81
17-17.0058.81
1857.1033.29
19-57.1033.29
2045.0050.54
21-45.0050.54
2267.510.00
23-67.510.00
2478.8018.90
25-78.8018.90
2645.0076.02
27-45.0076.02
2878.6339.17
29-78.6339.17
3073.0058.81
31-73.0058.81
3290.000.00
33-90.000.00
34107.0058.81
35-107.0058.81
36101.3739.17
37-101.3739.17
38135.0076.02
39-135.0076.02
40101.2018.90
41-101.2018.90
42112.490.00
43-112.490.00
44135.0050.54
45-135.0050.54
46122.9033.29
47-122.9033.29
48163.0058.81
49-163.0058.81
50123.9415.97
51-123.9415.97
52147.1033.29
53-147.1033.29
54135.000.00
55-135.000.00
56168.6339.17
57-168.6339.17
58146.0615.97
59-146.0615.97
60157.510.00
61-157.510.00
62168.8018.90
63-168.8018.90
64180.000.00

In the table above, azimuth is measured anticlockwise (left) from the front.

Practical Considerations

Lower Sounds

This dome arrangement has channels only on the horizontal or above, because objects may not be placed below the horizontal in many Spatial Audio systems, which have their origin in cinema.

Audio in the lower half of the O7A scene is typically not lost during decoding however. Instead, it is moved up to the horizontal, or made spatially ambiguous if panned more directly downwards.

For some applications, you might want to reflect the lower half of the scene into the upper half with the O7A Fold plugin from the O7A Music plugin library before decoding with these plugins.

Rendering the lower half of the scene is typically supported well in 3D audio rendering systems capable of handling Higher Order Ambisonics directly, such as Rapture3D Universal. In these cases, better imaging can generally be achieved by rendering from ambisonics directly rather than via these domes, which are intended for use with Spatial Audio systems that cannot do this.

Reverb

These Spatial Audio systems may apply additional reverberation during rendering, on top of what is already present in the mix. Different systems apply this reverberation in different ways, and may or may not allow it to be configured or disabled. It is generally a good idea to monitor for each possible playback method.

Rendering Quirks

It may be tempting to compensate for a directional inconsistencies in timbre or level produced by a particular renderer. This is not recommended in general, particularly where audio may be played back on different renderers, now or in the future.

Even on the same renderer, if head tracking is used, improvements made for one head orientation may make the mix worse in other head orientations.

Object Counts and Beds

Currently, Spatial Audio systems typically allow up to 128 channels of audio. However, delivery "profiles" will reduce the number of channels actually delivered to devices for final bed and object playback. For instance, the "MPEG-H 3D Audio Baseline" profile supports up to 24 audio objects to the device. If you have more objects in your mix than the delivery profile can handle, it is likely that the excess will be pre-rendered into a speaker bed (typically 7.1.2) or otherwise be merged together.

We don't particularly recommend use of speaker beds rather than objects for Spatial Audio delivery, not least because the rendering angles can be quite inconsistent. For instance, Front Left and Right are typically rendered on headphones at +/-45 degrees rather than the normal +/-30 degrees recommended on speakers.

The plugin is available in the O7A Spatial Audio plugin library.