Content for TS 26.119 Word version: 18.0.0
12 Metadata formats
12.1 General
12.2 Pose format
12.3 Action format
12.4 Available Visualization Space format
12.5 Device capabilities signalling
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12 Metadata formats p. 33
12.1 General p. 33
Several applications may require the exchange of real-time metadata information for about the XR session. For instance, split rendering applications and immersive communication services may require the UE to share Pose and action information pertaining to the user's current pose, to their input (e.g. pulling a trigger on the XR controller) or trackable pose. This clause defines the metadata formats for timed metadata of an XR session.
12.2 Pose format p. 33
The Pose format is used to share pose information, e.g. about predicted poses with the network.
Each predicted pose shall contain the associated predicted display time and an identifier of the XR space that was used for that pose.
Depending on the view configuration of the XR session, there could be different pose information for each view.
The payload of the message shall follow the structure defined in Table 12.2-1.
| Name | Type | Cardinality | Description |
|---|---|---|---|
| poseInfo | Object | 1..n | An array of pose information objects, each corresponding to a target display time and XR space. |
| poseTime | number | 1..1 | The time for which the current poses are predicted. This time is expressed in XR system time clock. |
| xrSpaceId | number | 0..1 | An identifier for the XR space in which the poses are expressed. |
| poses | Object | 1..n | An array that provides a list of the poses. For view poses, the first pose corresponds to the left view and the second to the right view. |
| trackableSpaceId | number | 0..1 | A unique identifier of the XR space of the trackable that was agreed upon during session setup. The pose corresponds to the origin of that trackableSpaceId expressed in the XR space identified by xrSpaceId. This is only applicable for trackable pose. |
| orientation | Object | 1..1 | Represents the orientation of the pose as a quaternion based on the reference XR space identified by xrSpaceId. |
| x | number | 1..1 | Provides the x coordinate of the quaternion. |
| y | number | 1..1 | Provides the y coordinate of the quaternion. |
| z | number | 1..1 | Provides the z coordinate of the quaternion. |
| w | number | 1..1 | Provides the w coordinate of the quaternion. |
| position | Object | 0..1 | Represents the position of the pose relative to the XR space identified by xrSpaceId. |
| x | number | 1..1 | Provides the x coordinate of the position vector. |
| y | number | 1..1 | Provides the y coordinate of the position vector. |
| z | number | 1..1 | Provides the z coordinate of the position vector. |
| confidence | number | 0..1 | Provides a confidence score that reflects the probability for this pose prediction to be correct. For the current pose or a pose in the past, the confidence value would be 1. The confidence can take a value between 0 and 1. |
| estimatedAtTime | number | 0..1 | The wall clock time when the pose estimation was made. (ref. T1) |
| fov | Object | 0..1 | Indicates the four sides of the field of view used for the projection of the corresponding XR view. This field is only present if these field of view values have changed from the last sent values. This is only applicable for view poses |
| angleLeft | number | 1..1 | The angle in radians of the left side of the field of view. For a symmetric field of view this value is negative. |
| angleRight | number | 1..1 | The angle in radians of the right side of the field of view. |
| angleUp | number | 1..1 | The angle in radians of the top part of the field of view. |
| angleDown | number | 1..1 | The angle in radians of the bottom part of the field of view. For a symmetric field of view this value is negative. |
12.3 Action format p. 35
Actions are grouped into action sets which may be activated and deactivated during the lifetime of an XR session. The action sets and actions are negotiated at the start of the split rendering session.
The content of the action message type shall the structure defined in Table 12.3-1.
| Name | Type | Cardinality | Description |
|---|---|---|---|
| actionSets | Object | 1..n | An array of active action sets, for which there is at least an action that has a state change. |
| actions | number | 1..n | An array of objects that conveys information about the actions of the parent action set. |
| identifier | string | 1..1 | A unique identifier of the action. |
| subactionPath | string | 1..1 | The sub-action path for which the state has changed. It abstracts a binding between an action and the hardware input associated to it by the XR runtime. |
| state | object | 1..1 | The state of the action that had a change in state. |
| lastChangeTime | number | 1..1 | The timestamp of the last change to the state of this action. |
| currentStateBool | Bool | 0..1 | The current Boolean state of the action |
| currentStateNum | number | 0..1 | The current numerical state of the action. |
| currentStateVec2 | Array | 0..1 | An array of numerical state values for the action. |
12.4 Available Visualization Space format p. 35
The XR Application may define a three-dimensional space within the user's real-word space that is suitable for rendering virtual objects called the Available Visualization Space. Such a space is defined with a shape which is either cube or sphere with the corresponding size and coordinates. In the case that the virtual scene is rendered by a remote entity (e.g. split rendering), this Available Visualization Space may be transmitted to this remote entity so that the composed AR objects remain within the defined Available Visualization Space. The method of calculating the Available Visualization Space is out of the scope of this document.
The content of the availableVisualizationSpace type shall follow the format defined in Table 12.4-1.
| Name | Type | Cardinality | Description |
|---|---|---|---|
| availableVisualizationSpace | Object | 0..1 | An object defining the coordinate of the available visualization space. |
| xrSpaceId | number | 0..1 | An identifier for the XR space in which the available visualization space is expressed. |
| cuboid | Object | 0..1* | The available visualization space in form of cuboid. The 3D coordinates are expressed in the XR Space identified by xrSpaceId. |
| x | float | 1 | Offset of the available visualization space starting point in the x direction. The value is in meters. |
| y | float | 1 | Offset of the available visualization space starting point in the y direction as defined by the Open XR coordinate system. The value is in meters. |
| z | float | 1 | Offset of the available visualization space starting point in the z direction. The value is in meters. |
| width | float | 1 | The width of available visualization space in the x direction as defined by the Open XR coordinate system. The value is in meters. |
| height | float | 1 | The height of available visualization space in the y direction. The value is in meters. |
| depth | float | 1 | The depth of available visualization space in the z direction. The value is in meters. |
| sphere | Object | 0..1* | The available visualization space in form of a sphere. The 3D coordinates are expressed in the XR Space identified by xrSpaceId |
| x | float | 1 | Offset of the available visualization space center in the x direction as defined by the Open XR coordinate system. The value is in meters. |
| y | float | 1 | Offset of the available visualization space center in the y direction. The value is in meters. |
| z | float | 1 | Offset of the available visualization space center in the z direction. The value is in meters. |
| radius | float | 1 | The radius of available visualization space. The value is in meters. |
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Only one of cuboid or sphere object shall exists.
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With this Available Visualization Space, a user may for instance avoid the virtual objects to be occluding other real objects in the scene, e.g. TV sets, people, etc., since an AR experience is achieved by the integration of visual objects into the user environment.
12.5 Device capabilities signalling p. 37
Device capabilities may be signalled using the format defined in Table 12.5-1.
| Name | Type | Cardinality | Description |
|---|---|---|---|
| deviceCapabilities | Object | 0..1 | Provides the supported device capabilities. |
| deviceType | string | 1...N | A list of device type identifiers formatted as URN defined in Table A-1 in Annex A. For each signalled device type identifier, the associated capabilities are supported by the sending device. |
| additionalCapabilities | string | 0...N | A list of additional media capability identifiers formatted as URN defined in Table A-2 in Annex A For each signalled media capability identifier, the associated capabilities are supported by the sending device. |
