A pg:Group MUST have exactly one string lv2:symbol. This symbol must be unique according to the same rules as the lv2:symbol for an lv2:Port, where group symbols and port symbols reside in the same namespace. In other words, a group on a plugin MUST NOT have the same symbol as another group or a port on that plugin. Rationale: Hosts or bindings may find it useful to construct an identifier to refer to groups for the same reasons this is useful for ports.
A Group MUST have at least one role assignment
A grouping of ports that can be logically considered a single "stream", e.g. two audio ports in a group may form a stereo stream. The pg:source predicate can also be used to describe this correspondence between separate ports/groups.
A RoleAssignment MUST have exactly one index.
A RoleAssignment MUST have exactly one role.
All group definitions MUST define the order of channels. Note that this does not have anything to do with port indices, this information is only defined here for use by other extensions. For simply assigning groups and roles to a basic LV2 plugin, index is irrelevant.
Indicates that a group always has a port with a particular role.
Indicates that a group may have a port with a particular role.
Indicates that this port or group should be considered a "side chain" of some other port or group. The precise definition of "side chain" depends on the plugin, but in general this group should be considered a modifier to some other group, rather than an independent input itself.
Indicates that this group is a child of another group. This property has no meaning with respect to plugin execution, but the host may find this information useful (e.g. to provide a compact user interface). Note that all groups on a plugin MUST have a unique symbol with respect to the plugin as documented for pg:Group, i.e. sub-groups must have a unique symbol among all groups and ports on the plugin.
Indicates that this port or group should be considered the "result" of some other port or group. This property only makes sense on groups with outputs when the source is a group with inputs. This can be used to convey a relationship between corresponding input and output groups with different types, e.g. a mono->stereo plugin.
Indicates that this group should be considered the "main" inputs/outputs of the plugin, e.g. it probably makes sense to just connect main groups and set some controls. A plugin MUST NOT have more than one :mainGroup property. High-level hosts that simply want to insert an plugin in a given stream should use this property to determine where the plugin 'fits'.
Indicates that this port is a part of a group of ports on the plugin. Ports that have a meaningful "role" that may be useful to hosts SHOULD also have a :role property, otherwise ports in the group have no meaningful order.
The role of a port with respect to its plugin or group. If the port is a member of a group (has an :inGroup property) the role is relevant with respect to that group. Otherwise the role is relevant with respect to the plugin.
Indicates that this port has a particular role with respect to its enclosing plugin or group (whichever is smaller). A port may have several roles if it makes sense to do so (though some Role or Group definition may forbid this).
"Discrete" channel configurations. These groups are divided into channels where each represents a particular speaker location. The position of sound in one of these groups depends on a particular speaker configuration.
"Ambisonic" channel configurations. These groups are divided into channels which together represent a position in an abstract n-dimensional space. The position of sound in one of these groups does not depend on a particular speaker configuration; a decoder can be used to convert an ambisonic stream for any speaker configuration.
Ambisonic B stream of horizontal order 1 and peripheral order 0.
Ambisonic B stream of horizontal order 1 and peripheral order 1.
Ambisonic B stream of horizontal order 2 and peripheral order 0.
Ambisonic B stream of horizontal order 2 and peripheral order 1.
Ambisonic B stream of horizontal order 2 and peripheral order 2.
Ambisonic B stream of horizontal order 3 and peripheral order 0.
Ambisonic B stream of horizontal order 3 and peripheral order 1.
Ambisonic B stream of horizontal order 3 and peripheral order 2.
Ambisonic B stream of horizontal order 3 and peripheral order 3.
A group representing a set of associated controls.