Main Content

vision.labeler.loading.VideoSource class

Package: vision.labeler.loading
Superclasses: vision.labeler.loading.MultiSignalSource

Load signals from video sources into Ground Truth Labeler app

Description

The vision.labeler.loading.VideoSource class creates an interface for loading signals from video data sources into the Ground Truth Labeler app. In the Add/Remove Signal dialog box of the app, when Source Type is set to Video, this class controls the parameters in that dialog box.

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

The default implementation of this class loads the video formats accepted by the VideoReader object.

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

Creation

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

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

Description

example

vidSource = vision.labeler.loading.VideoSource creates a VideoSource object for loading signals from video data sources. To specify the data source and the parameters required to load the source, use the loadSource method.

Properties

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

Attributes:

GetAccess
public
Constant
true
NonCopyable
true

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

Attributes:

GetAccess
public
Constant
true
NonCopyable
true

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

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

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

FieldDescriptionRequired or Optional
Timestamps

Timestamps for the video 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 video file, then the structure does not include this field, and the SourceParams property is empty, [].

Attributes:

GetAccess
public
SetAccess
protected

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

Attributes:

GetAccess
public
SetAccess
protected

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

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

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

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Examples

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Create a video source from a video on the MATLAB® search path. Load the source name into the VideoSource object. The video has no source parameters needed to load it, so sourceParams is empty.

sourceName = 'caltech_cordova1.avi';
sourceParams = [];

vidSource = vision.labeler.loading.VideoSource;
loadSource(vidSource,sourceName,sourceParams);

Read the first frame from the video. Display the frame.

signalName = vidSource.SignalName;
I = readFrame(vidSource,signalName,1);

figure
imshow(I)

Tips

  • You can 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.VideoSource

Introduced in R2020a