Output Autogain Stereo

s3g Output Autogain Stereo folds a multichannel REAPER track down to a true stereo CLAP output. It is meant for auditioning multichannel material when the session is not using an ambisonic decoder.

The plugin accepts up to 128 input channels and returns outputs 1-2 as stereo. It uses layout models, width, rotation, weighting, 3D distance, 3D attenuation, autogain, and output trim to make the fold-down controllable.

Output Autogain Stereo fold-down controls, layout visualization, and stereo meters — Output Autogain Stereo with fold-down controls, layout visualization, and active stereo meters.

Workflow

Insert Output Autogain Stereo on the wide source track, then set the REAPER pins and IN count to include the intended channels.
Route outputs 1-2 to the stereo main speakers or headphones, enable zeroing for unmapped output channels when needed, and begin playback.
Choose a layout model and set width, rotation, weighting, distance, and attenuation for the source geometry.
Select an autogain mode, then adjust OUT while watching the stereo meters.
Compare the fold-down with the wide source and confirm that no higher track channels bypass the plugin.

Signal Flow

Assign a pan and gain value to each included input channel.
Sum the weighted channels to the left and right outputs.
Apply autogain and output gain.

MC to Stereo fold-down diagram — Many input channels are placed in a layout model, converted to stereo pan/gain pairs, then summed to outputs 1-2.

Layout Models

LAY chooses how input channels are interpreted before the stereo fold-down. The models are:

Layout	Use
Ring projection	Places channels around a circle and folds rear positions into stereo using layout weighting.
Linear left-right	Spreads channels in order from left to right.
Odd/even stereo	Sends odd/even channel pairs toward left and right.
Center-out	Keeps middle channels near center and spreads outer channels outward.
Pair-preserving	Keeps adjacent channel pairs close while distributing pairs across stereo.
Sphere projection	Uses 3D positions where elevation and rear placement can affect pan and gain.
Hemisphere projection	Uses an upper dome model for layouts that do not need lower speakers.
Cube projection	Uses an 8-point cube-style model for upper/lower spatial weighting.

3D Controls

The 3D layouts separate placement from level. DST changes how far elevated or lowered points sit from the center of the projection. ATT changes how much height and rear position reduce gain.

3D layout control diagram for MC to Stereo — `DST` exaggerates or collapses the 3D point spread. `ATT` changes gain attenuation for height and rear placement.

Controls

Control	Meaning
IN	How many plugin input channels are included in the fold-down.
WDTH	Stereo width. Low values collapse inward; high values exaggerate left/right placement.
ROT	Rotates ring and 3D layouts before they are folded to stereo.
LAY	Chooses the layout model.
WGT	Controls how strongly the layout shape affects rear or grouped channel positions.
ATT	3D attenuation. In 3D layouts, height and rear position can reduce gain.
DST	3D distance. In 3D layouts, upper and lower positions spread away from or toward center.
AGN	Autogain mode: off, power/sqrt(N), or energy sum.
OUT	Final stereo output gain trim.

REAPER Pins

The plugin has a true stereo output bus, but REAPER may still preserve existing audio on unmapped track channels. If a following meter still shows channels above 2, open REAPER's plugin pin connector and enable Zero out unmapped output channels.

REAPER pin connector note for MC to Stereo — Use REAPER's pin connector to make sure only the plugin's stereo outputs continue after the fold-down.

When To Use It

Audition a multichannel track quickly through stereo speakers or headphones.
Check a multichannel render without setting up an ambisonic decoder.
Compare layout fold-down choices while building wider-channel material.

For ambisonic monitoring, use an appropriate decoder instead. This plugin is a practical stereo fold-down, not an HOA decode stage.