Apply focus to a first order ambisonic signal (B-format) along the z-axis.
The B-format signal, an array: [w, x, y, z]
The distortion angle, in radians. -pi/2 to pi/2
Output will be multiplied by this value.
This value will be added to the output.
Focus is a normalised dominance variant, specified in terms of a distortion angle. Positive values of angle maintain gain at
[0, pi/2], while reducing at
[0, -pi/2]. Negative values do the inverse. The default, 0, results in no change.
In contrast with zoom, gain is maintained at 0dB in the direction of distortion.
Please see various examples here.