vision.labeler.loading.VelodyneLidarSource Class

Namespace: vision.labeler.loading
Superclasses: vision.labeler.loading.MultiSignalSource

Load signals from Velodyne lidar sources into Ground Truth Labeler app

Since R2020a

Description

The vision.labeler.loading.VelodyneLidarSource class creates an interface for loading signals from Velodyne^® packet capture (PCAP) lidar data sources into the Ground Truth Labeler app. In the Add/Remove Signal dialog box of the app, when Source Type is set to Velodyne Lidar, this class controls the parameters in that dialog box.

To access this dialog box, in the app, select Import > Add Signals.

The default implementation of this class loads Velodyne PCAP files from the device models accepted by the velodyneFileReader function.

The vision.labeler.loading.VelodyneLidarSource class is a handle class.

Creation

When you export labels from a Ground Truth Labeler app session that contains Velodyne lidar sources, the exported groundTruthMultisignal object stores instances of this class in its DataSource property.

To create a VelodyneLidarSource object programmatically, such as when programmatically creating a groundTruthMultisignal object, use the vision.labeler.loading.VelodyneLidarSource function (described here).

Syntax

velodyneSource = vision.labeler.loading.VelodyneLidarSource

Description

velodyneSource = vision.labeler.loading.VelodyneLidarSource creates a VelodyneLidarSource object for loading signals from Velodyne lidar data sources. To specify the data source and the parameters required to load the source, use the loadSource method.

Properties

Name — Name of source type

"Velodyne Lidar" (default) | string scalar

Name of the type of source that this class loads, specified as a string scalar.

Attributes:

GetAccess	public
Constant	true
NonCopyable	true

Description — Description of class functionality

"A Velodyne file reader" (default) | string scalar

Description of the functionality that this class provides, specified as a string scalar.

Attributes:

GetAccess	public
Constant	true
NonCopyable	true

SourceName — Name of data source

[] (default) | string scalar

Name of the data source, specified as a string scalar. Typically, SourceName is the name of the file from which the signal is loaded.

Attributes:

GetAccess	public
SetAccess	protected

SourceParams — Parameters for loading Velodyne lidar signal from data source

[] (default) | structure

Parameters for loading a Velodyne lidar signal from a data source, specified as a structure.

This table describes the required and optional fields of the SourceParams structure.

Field	Description	Required or Optional
Timestamps	Timestamps for the Velodyne lidar signal, specified as a cell array containing a single duration vector of timestamps. In the Add/Remove Signal dialog box of the app, if you set the Timestamps parameter to From Workspace and read the timestamps from a variable in the MATLAB® workspace, then the SourceParams property stores these timestamps in the Timestamps field.	Optional In the Add/Remove Signal dialog box of the app, if you set the Timestamps parameter to From File and read the timestamps from the Velodyne PCAP file, then the structure does not include this field.
DeviceModel	Velodyne device model name, specified as one of these options. 'VLP16' (default) — VLP-16 device model 'PuckLITE' — Puck LITE device model 'PuckHiRes' — Puck Hi-Res device model 'VLP32C' — VLP-32C device model 'HDL32E' — HDL-32E device model 'HDL64E' — HDL-64E device model 'VLS-128' — VLS-128 device model If you specify the incorrect device model for your Velodyne PCAP file, the app loads an improperly calibrated point cloud. In the Add/Remove Signal dialog box of the app, select the device model from the Device Model parameter. The Calibration File parameter updates to the calibration file of the selected device model.	Required
CalibrationFile	Name of the Velodyne calibration XML file, specified as a character vector or string scalar. To specify one of the calibration files included with your MATLAB installation, at the MATLAB command prompt, enter this code. Replace <DeviceModel> with the name of the device model that you specify in the DeviceModel field of this structure (without quotes). calibrationFile = fullfile( ... matlabroot,'toolbox', ... 'shared','pointclouds','utilities', ... 'velodyneFileReaderConfiguration', ... '<DeviceModel>.xml') By default, the CalibrationFile field is set to the full path to the VLP16.xml file, which is the calibration file for the VLP-16 device model. In the Add/Remove Signal dialog box of the app, when you change the Device Model parameter selection, the Calibration File parameter updates to the corresponding calibration file for the selected device model. You can also browse for or enter a path to a different calibration file in the Calibration File box.	Required

For more details on device models and calibration files, see the velodyneFileReader object reference page.

Attributes:

GetAccess	public
SetAccess	protected

SignalName — Names of signals in data source

[] (default) | string vector

Names of the signals that can be loaded from the data source, specified as a string vector.

Attributes:

GetAccess	public
SetAccess	protected

SignalType — Types of signals in data source

[] (default) | vector of vision.labeler.loading.SignalType enumerations

Types of the signals that can be loaded from the data source, specified as a vector of vision.labeler.loading.SignalType enumerations. Each signal listed in the SignalName property is of the type in the corresponding position of SignalType.

Attributes:

GetAccess	public
SetAccess	protected

Timestamp — Timestamps of signals in data source

[] (default) | cell array of duration vectors

Timestamps of the signals that can be loaded from the data source, specified as a cell array of duration vectors. Each signal listed in the SignalName property has the timestamps in the corresponding position of Timestamp.

Attributes:

GetAccess	public
SetAccess	protected

NumSignals — Number of signals in data source

0 (default) | integer

Number of signals that can be read from the data source, specified as a nonnegative integer. NumSignals is equal to the number of signals in the SignalName property.

Attributes:

GetAccess	public
SetAccess	public
Dependent	true
NonCopyable	true

Methods

Public Methods

customizeLoadPanel	customizeLoadPanel(sourceObj,panel) Customize the loading panel for the data source object. In the loading dialog box of the app, this method is invoked when you select the data source type from the Source Type list.
getLoadPanelData	[sourceName,sourceParams] = getLoadPanelData(sourceObj) Obtain the data needed to load the data source object currently selected in the loading panel. In the loading dialog box of the app, this method is invoked when you add a source. The method returns these outputs. sourceName is a string capturing the name of the data source object. sourceParams is a structure with fields containing the parameters required to load the data source object. Both of these outputs are passed to the loadSource method.
loadSource	loadSource(sourceObj,sourceName,sourceParams) Load a data source object into the app. In the loading dialog box of the app, this method is invoked after you add a source and the getLoadPanelData method executes successfully. This method is also invoked when you load the data source object into the MATLAB workspace. When you load the data source object, MATLAB expects that the source has the name sourceName and parameters sourceParams that are needed to load that source and read data from it.
readFrame	frame = readFrame(sourceObj,signalName,tsIndex) Read a frame of data from a signal contained in a data source object at the specified timestamp index. The index must be in the bounds of the length of the timestamps for that signal.
loadPanelChecker	loadPanelChecker Check the load panel for the loading dialog box of the app. This method opens a dialog box similar to the loading dialog box that you open from the Open menu on the app toolstrip. Use this method to preview how the customizeLoadPanel method populates the loading panel for the selected data source object. Static true

Examples

Create Velodyne Lidar Source

Specify the name of the Velodyne® lidar data source, a packet capture (PCAP) file.

sourceName = fullfile(toolboxdir('vision'),'visiondata', ...
    'lidarData_ConstructionRoad.pcap');

Specify information needed to load the source, including the device model of the lidar and the calibration file.

sourceParams = struct;
sourceParams.DeviceModel = 'HDL32E';
sourceParams.CalibrationFile = fullfile(matlabroot,'toolbox','shared', ...
    'pointclouds','utilities','velodyneFileReaderConfiguration', ...
    'HDL32E.xml');

Create the Velodyne lidar data source. Load the data source path, device model, and calibration file path into the VelodyneLidarSource object.

velodyneSource = vision.labeler.loading.VelodyneLidarSource;
loadSource(velodyneSource,sourceName,sourceParams);

Read the first frame from the source. Display the frame.

signalName = velodyneSource.SignalName;
pc = readFrame(velodyneSource,signalName,1);

figure
pcshow(pc)

Tips

• You can use this class as a starting point for creating a custom data source loading class. To view the source code for this class, use this command:

  edit vision.labeler.loading.VelodyneLidarSource

Version History

Introduced in R2020a