SceneLabelData
Description
The SceneLabelData
object stores ground truth data for scene
label definitions defined in a groundTruthMultisignal
object.
Creation
When you export a groundTruthMultisignal
object from a Ground
Truth Labeler app session, the SceneLabelData
property of the
exported object stores the scene labels as a SceneLabelData
object. To create
a SceneLabelData
object programmatically, use the
vision.labeler.labeldata.SceneLabelData
function (described
here).
Description
creates an object containing scene label data for multiple signals. The created object,
sceneLabelData
= vision.labeler.labeldata.SceneLabelData(labelNames
,labelData
)sceneLabelData
, contains properties with the scene label names
listed in labelNames
. These properties store the corresponding scene
label data specified by labelData
.
Input Arguments
labelNames
— Scene label names
string array
Scene label names, specified as a string array. Specify the names of all scene
labels present in the groundTruthMultisignal
object you are creating.
You can get the scene label names from an existing
groundTruthMultisignal
object by accessing the
LabelDefinitions
property of that object. Use this code and
replace gTruth
with the name of a
groundTruthMultisignal
object variable.
isSceneLabel = gTruth.LabelDefinitions.LabelType == 'Scene';
gTruth.LabelDefinitions.Name(isSceneLabel)
In an exported groundTruthMultisignal
object, the
SceneLabelData
object contains a label data property for every
scene label, even if some scene labels do not have label data.
The properties of the created SceneLabelData
object have the
names specified by labelNames
.
Example: ["sunny" "rainy" "urban" "rural"]
labelData
— Scene label data for each label
cell array of duration
matrices
Scene label data for each label, specified as a cell array of duration
matrices. Each matrix in the cell array contains data for the
scene label in the corresponding position of the labelNames
input. The SceneLabelData
object stores each matrix in a property
that has the same name as that signal.
Each scene label matrix is of size N-by-2. Each row in this
matrix corresponds to a time range for which that scene label has been applied.
N is the number of time ranges. Rows in the matrix are of the
form [rangeStart, rangeEnd]
, where rangeStart
and rangeEnd
specify the start and end of a time range for an
applied scene label.
Row elements are of type duration
and must be within the
range of the minimum and maximum of all the timestamps in the
groundTruthMultisignal
object. If a scene label is not applied,
then specify an empty matrix.
Example: seconds([0 5; 10 20])
specifies a
duration
matrix corresponding to one scene label in a
groundTruthMultisignal
object. Units are in seconds. The scene
label has been applied from 0 to 5 seconds and again from 10 to 20 seconds, across all
signals in the object. Specify this matrix as part of a cell array containing matrices
for additional scene labels.
Properties
SceneLabelName1,...,SceneLabelNameN
— Scene label data for each label (as separate properties)
duration
matrices
Scene label data, specified as duration
matrices. The SceneLabelData
object contains one
property per scene label definition, where each property contains a
duration
matrix of scene label data corresponding to that scene
label.
When exporting a SceneLabelData
object from a Ground Truth
Labeler app session, the property names correspond to the scene label names
stored in the LabelDefinitions
property of the exported
groundTruthMultisignal
object.
When creating a SceneLabelData
object programmatically, the
labelNames
and labelData
input arguments
define the property names and values of the created object.
Suppose you want to create a groundTruthMultisignal
object
containing scene labels that describe whether the scene is sunny, rainy, urban, or
rural. Specify the scene labels in a string array, labelNames
.
labelNames = ["sunny" "rainy" "urban" "rural"];
Store the label data for each scene label in a cell array of matrices,
labelData
. Each matrix contains the data for the corresponding
scene label in labelNames
.
labelData = {sunnyData,rainyData,urbanData,ruralData}
1×4 cell array {1×2 duration} {2×2 duration} {0×0 duration} {4×2 duration}
The SceneLabelData
object, sceneData
, stores
this data in the property with the corresponding signal name. You can specify
sceneData
in the SceneLabelData
property of
a groundTruthMultisignal
object.
sceneData = vision.labeler.labeldata.SceneLabelData(labelNames,labelData)
sceneData = SceneLabelData with properties: rainy: [2×2 duration] sunny: [0 sec 10.15 sec] rural: [4×2 duration] urban: [0×0 duration]
Object Functions
labelDefinitionsAtTime | Get scene label definition names at specified timestamp |
labelDataAtTime | Get scene label data at specified timestamps |
Examples
Create Ground Truth from Multiple Signals
Create ground truth data for a video signal and a lidar point cloud sequence signal that captures the same driving scene. Specify the signal sources, label definitions, and ROI and scene label data.
Create the video data source from an MP4 file.
sourceName = '01_city_c2s_fcw_10s.mp4';
sourceParams = [];
vidSource = vision.labeler.loading.VideoSource;
vidSource.loadSource(sourceName,sourceParams);
Create the point cloud sequence source from a folder of point cloud data (PCD) files.
pcSeqFolder = fullfile(toolboxdir('driving'),'drivingdata','lidarSequence'); addpath(pcSeqFolder) load timestamps.mat rmpath(pcSeqFolder) lidarSourceData = load(fullfile(pcSeqFolder,'timestamps.mat')); sourceName = pcSeqFolder; sourceParams = struct; sourceParams.Timestamps = timestamps; pcseqSource = vision.labeler.loading.PointCloudSequenceSource; pcseqSource.loadSource(sourceName,sourceParams);
Combine the signal sources into an array.
dataSource = [vidSource pcseqSource]
dataSource = 1x2 heterogeneous MultiSignalSource (VideoSource, PointCloudSequenceSource) array with properties: SourceName SourceParams SignalName SignalType Timestamp NumSignals
Create a table of label definitions for the ground truth data by using a labelDefinitionCreatorMultisignal
object.
The
Car
label definition appears twice. Even thoughCar
is defined as a rectangle, you can draw rectangles only for image signals, such as videos. ThelabelDefinitionCreatorMultisignal
object creates an additional row for lidar point cloud signals. In these signal types, you can drawCar
labels as cuboids only.The label definitions have no descriptions and no assigned colors, so the
Description
andLabelColor
columns are empty.The label definitions have no assigned groups, so for all label definitions, the corresponding cell in the
Group
column is set to'None'
.Road
is a pixel label definition, so the table includes aPixelLabelID
column.No label definitions have sublabels or attributes, so the table does not include a
Hierarchy
column for storing such information.
ldc = labelDefinitionCreatorMultisignal; addLabel(ldc,'Car','Rectangle'); addLabel(ldc,'Truck','ProjectedCuboid'); addLabel(ldc,'Lane','Line'); addLabel(ldc,'Road','PixelLabel'); addLabel(ldc,'Sunny','Scene'); labelDefs = create(ldc)
labelDefs = 7x7 table Name SignalType LabelType Group Description LabelColor PixelLabelID _________ __________ _______________ ________ ___________ __________ ____________ {'Car' } Image Rectangle {'None'} {' '} {0x0 char} {0x0 double} {'Car' } PointCloud Cuboid {'None'} {' '} {0x0 char} {0x0 double} {'Truck'} Image ProjectedCuboid {'None'} {' '} {0x0 char} {0x0 double} {'Lane' } Image Line {'None'} {' '} {0x0 char} {0x0 double} {'Lane' } PointCloud Line {'None'} {' '} {0x0 char} {0x0 double} {'Road' } Image PixelLabel {'None'} {' '} {0x0 char} {[ 1]} {'Sunny'} Time Scene {'None'} {' '} {0x0 char} {0x0 double}
Create ROI label data for the first frame of the video.
numVideoFrames = numel(vidSource.Timestamp{1}); carData = cell(numVideoFrames,1); laneData = cell(numVideoFrames,1); truckData = cell(numVideoFrames,1); carData{1} = [304 212 37 33]; laneData{1} = [70 458; 311 261]; truckData{1} = [309,215,33,24,330,211,33,24]; videoData = timetable(vidSource.Timestamp{1},carData,laneData, ... 'VariableNames',{'Car','Lane'});
Create ROI label data for the first point cloud in the sequence.
numPCFrames = numel(pcseqSource.Timestamp{1}); carData = cell(numPCFrames, 1); carData{1} = [27.35 18.32 -0.11 4.25 4.75 3.45 0 0 0]; lidarData = timetable(pcseqSource.Timestamp{1},carData,'VariableNames',{'Car'});
Combine the ROI label data for both sources.
signalNames = [dataSource.SignalName]; roiData = vision.labeler.labeldata.ROILabelData(signalNames,{videoData,lidarData})
roiData = ROILabelData with properties: video_01_city_c2s_fcw_10s: [204x2 timetable] lidarSequence: [34x1 timetable]
Create scene label data for the first 10 seconds of the driving scene.
sunnyData = seconds([0 10]);
labelNames = ["Sunny"];
sceneData = vision.labeler.labeldata.SceneLabelData(labelNames,{sunnyData})
sceneData = SceneLabelData with properties: Sunny: [0 sec 10 sec]
Create a ground truth object from the signal sources, label definitions, and ROI and scene label data. You can import this object into the Ground Truth Labeler app for manual labeling or to run a labeling automation algorithm on it. You can also extract training data from this object for deep learning models by using the gatherLabelData
function.
gTruth = groundTruthMultisignal(dataSource,labelDefs,roiData,sceneData)
gTruth = groundTruthMultisignal with properties: DataSource: [1x2 vision.labeler.loading.MultiSignalSource] LabelDefinitions: [7x7 table] ROILabelData: [1x1 vision.labeler.labeldata.ROILabelData] SceneLabelData: [1x1 vision.labeler.labeldata.SceneLabelData]
Tips
To create a
groundTruthMultisignal
object containing ROI label data but no scene label data, specify theSceneLabelData
property as an empty array. To create this array, at the MATLAB® command prompt, enter this code.sceneData = vision.labeler.labeldata.SceneLabelData.empty
Version History
Introduced in R2020a
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