Amplitude Panning
All of the parameters listed here are available in the Algorithm tab of Amplitude Panning buses.
VBAP / VBIP
VBAP and VBIP are both panning algorithms, based on level differences between the loudspeakers. VBAP is based on amplitude differences whereas VBIP works with intensity differences.
Speaker Layout
Requirements
VBAP and VBIP were designed to work on 2D and 3D surround speaker systems. Try to use speakers that are as regularly spaced as possible across the entire setup, for a maximum homogeneity.
However, VBAP and VBIP are efficient on quite asymmetric layouts, as long as there are enough speakers on a trajectory to offer smooth variations. Check for possible optimizations in "Amplitude Panning Algorithms Optimization", page 77.
- This algorithm requires the loudspeaker layout to include frontal and surround speakers.
- The center of the coordinates system needs to be inside the speaker layout.
HOLOPHONIX will display an error message in the 'LOG' section if an invalid speaker layout is used. Otherwise, speaker positioning is free.
Virtual loudspeakers
If the setup you have is not valid for the algorithm, you can still use 'virtual' loudspeakers that will not be connected to any real loudspeaker, but will allow the algorithm to see a valid setup.
First, create a new bus with the right amount of loudspeakers (real speakers and virtual speakers), and assign the first bus outputs to the real loudspeakers. Open the bus 'SPEAKER PARAMETERS', deactivate the 'LINKED TO SPEAKER POSITION' mode and manually adjust the position of the additional loudspeakers to match the algorithm requirements.
For example, if you want to use VBAP or VBIP algorithms on a frontal speaker layout (with no surround speakers), you will need to use 'virtual' speakers placed at the rear of the venue (i.e. behind of the origin of the coordinates system).
Elevation Layout (3D)
On the elevation plane, VBAP and VBIP offers better results for setups where the different layers are organized in staggered rows (i.e. the speakers are not aligned with one another), thus forming triangles in the elevation plane. If speakers are all aligned in the elevation plane (forming squares), use LBAP, as it was designed for such layouts.
Optimizations
When using VBAP or VBIP on 3D setups that are open at the top, the speaker triplets computed by the algorithm can end up being not optimal for the setup. For the algorithm to ensure a good accuracy in source localization, the setup would have required a speaker at the top or the bottom of the setup.
Without such speaker when a source is moved upwards (or downwards), its signal will be sent to three speakers, where the user would have selected two loudspeakers.
Adding an imaginary (phantom) loudspeaker causes the algorithm to compute new speaker triplets in the problematic area. The signal sent to the phantom speaker being ignored, the algorithm ends up using only two speakers instead of three.
However, if a source is positioned in the same direction as the phantom speaker, its audio will be lost, as the phantom speaker signal is simply dismissed.
Parameters
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. You can choose to Bypass the Spread.
Divergence Radius
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.
By default, Divergence is not applied as the Bypass button is activated. Click on Bypass to activate Divergence Radius.
Phantom Speaker
Available in 3D only, the phantom speakers allows you to create a virtual speaker placed above (Top) or under (Bottom) the speaker setup. When speakers are not evenly distributed, this can solve sound homogeneity issues if a sound source is sent at the top or at the bottom of the setup.
Angular 2D
Angular 2D performs a pairwise amplitude panning by evaluating the angle between the source and the two closest speakers. It offers similar results to VBAP2D, the only difference being the way the gains evolve with the source position, that is very slightly different.
Angular 2D is a legacy algorithm that is mainly provided for retro compatibility. However, it is still a good competitor to VBAP2D.
Parameters
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. You can choose to Bypass the Spread.
Divergence Radius
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.
By default, Divergence is not applied as the Bypass button is activated. Click on Bypass to activate Divergence Radius.
LBAP
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 loudspeakers are aligned with one another on the vertical axis or when the layer are not homogeneous.
It is often a good alternative to VBAP when the loudspeaker setup is not suited for VBAP.
Speaker Layout
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
- Each layer is operated by the VBAP 2D 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.
Parameters
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. You can choose to Bypass the Spread.
Divergence Radius
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.
By default, Divergence is not applied as the Bypass button is activated. Click on Bypass to activate Divergence Radius.
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.
KNN
KNN selects the k loudspeakers closest to the source position, and applies level differences between them. The gain differences are calculated based on the distance between the source and the selected loudspeakers.
The quantity of speakers k is chosen by the user with the Neighbors parameter.
KNN allows a very flexible spatialization, as the loud-speakers can have any layout.
Parameters
Bus mode
Activate this parameter to switch your bus to 2D mode. In 2D mode, the height (Z) of sources or speakers will have no effect on the resulting spatialization.
Spread
Use the spread to change the apparent width of sources spatialized by the bus.
Unlike other algorithms, the KNN Spread doesn't rely on replicas of the virtual sources.
The gain differences between the loudspeakers selected by the algorithm is progressively reduced when the KNN Spread is increased. At 100% Spread, there is no level differences between the selected loudspeakers.
You can choose to Bypass the Spread.
For this algorithm, the Spread is limited to the selected k loudspeakers (set by Neighbors).
Neighbors
Sets the maximum quantity of neighboring loudspeakers used by the algorithm for each virtual source.
This setting can be use along with Max Distance to set more precisely how loudspeakers are selected by the algorithm.
The maximum allowed number of speakers is the number of channels in the KNN bus.
Max Distance
This allows to configure a maximum distance after which the loudspeakers cannot contribute to the spatialization of each source. This setting is applied within the k Neighbors parameter. It ranges from 0 to 100 meters.
Exponent
This parameter interacts with the way distances are considered by the algorithm. Changing this parameter will have an impact on the gains repartition between the loudspeakers for each source, depending on their distance to the source. At its default value 1, the algorithm will use conventional Euclidian distances.
- When the Exponent is set to a value higher than 1, the furthest speakers will contribute less,
- Under 1, the furthest speakers will contribute more.
- Under 0, the closet loudspeaker will contribute less than the speakers that are further away.
- At -1, the gain values are completely inverted.