O3A Upmixer - 5.1

Host Support

Host Type	Support
AAX	Yes
VST2	Yes

Audio

	Channels	Content
Input	6	5.1 Surround
Output	16	O3A

Controls

Corners
Mode
LFE Gain

Description

This plugin takes a surround mix prepared for a 5.1 system and converts it to third order ambisonics (O3A).

Channels

The channel ordering used is:

Channel	AAX	VST
1	Front Left	Front Left
2	Front Centre	Front Right
3	Front Right	Front Centre
4	Left Surround	LFE
5	Right Surround	Side Left
6	LFE	Side Right

The plugin is available in the O3A Upmixers plugin library.

Controls

Control: Corners

The corner layout lets you tell the processor how the 5.1 mix was prepared, as this can help the accuracy of the spatial imaging. ITU is the most common option.

Corner Layout	Description
ITU	In principle, the speakers of a 5.1 system should be set out using ITU angles. From front centre, this recommends front left and right speakers be at +30 or -30 degrees and side speakers be at +110 or -110 degrees. ITU layouts are common in studios and are a common way to mix 5.1.
Square	In practice, many 5.1 speaker systems are set up with the corner speakers set out in what is roughly a square and some mixes are put together on this basis. If you know that's the case, switch the corner layout to Square.

Control: Mode

Three modes are supported, "Inferred", "Studio" and "Virtual". Generally, "Inferred" or "Studio" are recommended.

Mode	Description
Inferred	This mode is optimised for use with material that has been mixed using conventional panning techniques, such as equal-power panning or VBAP. The approach produces smooth transitions when sounds pass between speaker locations.
Studio	This mode is optimised for use with material that has been mixed using 'pairwise' panning, for instance in Pro Tool's surround panner. The approach produces smooth transitions when sounds pass between speaker locations. In this mode, the corner layout is always assumed to be Square.
Virtual	This mode simply places each of the main (non-LFE) audio channels in their appropriate speaker direction. This can be worth trying when the mix has not been put together by conventional panning and the channels have a complex phase relationship.

Control: LFE Gain

Audio from the LFE channel can be mixed into the output by setting this dial. It is added to the stream as an omnidirectional signal.

O3A Upmixers