LBAP (Layer Based Amplitude Panning) Bus

LBAP is an amplitude panning algorithm, optimized for 3D setups where the loudspeakers are forming horizontal layers. It is ideal for setups where the elevation loudpseakers are aligned with one another on the vertical axis or when the layer are not homogeneous.

It is often a good alternative to VABP when the loudspeaker setup is not suited for VABP.

Working Principle#

This algorithm performs an amplitude panning using the two layers surrounding the source. On each of these two layers, it applies a pairwise amplitude panning (VABP 2D) on the two speakers closest to the source. It then applies a level weighting (or crossfade) between the two selected layers, based on the elevation of the source.

If a source is perfectly aligned with one loudspeaker, then only this speaker is fed with the source signal. When a source is positioned between two speakers, only those two will be used. Otherwise, the algorithm will always use the four loudspeakers surrounding the source.

Speaker Placements Requirements#

LBAP was designed to work on 3D surround speakers systems organized by layers. Check for possible optimizations by reading the Guide to Amplitude Panning

Speaker Placement Requirements
  • Each layer is operated by the VBAP2D algorithm. Make sure that each layer respects the layout requirements for this algorithm.
  • The setup needs to be organized in clear layers i.e., the speakers of each layer must have exactly the same z Coordinate. If necessary, use the Speaker Parameters to adjust the speaker positioning of the LBAP bus.
  • Make sure to choose the right Layering option for your setup. Most of the time Based on Z is the best option.

Settings#

Spread#

Use the spread to change the apparent width of sources spatialized by the bus. This parameter spreads replicas of each source in multiple directions around the position of the source. It can be used for artistic purposes or to smooth the width and coloration of a moving source.

Divergence#

The divergence applies a spread to the sources progressively, when they start entering the divergence circle (2D) or the sphere (3D) defined by the Radius parameter.

  • When the source's AED Distance is higher than the radius, no spread is applied.
  • When the source's AED Distance lower than the radius, a spreading is progressively applied, reaching 100% when the source is at the center of the coordinates system.

Layering#

Adjust this setting according to the way the speaker layers are organized:

  • Choose Based on elevation when all the speakers on each layer share the same elevation (aed coordinates),
  • Choose Based on z, if they share the same height (xyz coordinates).

Algorithm#

Sets the 2D algorithm that is used by LBAP on each layer.