Table of Contents

Class LicensePlateRecognizerBlock

Namespace
VisioForge.Core.MediaBlocks.AI
Assembly
VisioForge.Core.AI.dll

A license plate recognizer (ANPR/LPR) media block. Runs a specialized two-stage pipeline: a dedicated license-plate detector locates plates in the frame, each plate is cropped, and a plate-specific OCR model reads its characters. Implements the VisioForge.Core.MediaBlocks.MediaBlock. Implements the VisioForge.Core.MediaBlocks.IMediaBlockInternals.

public class LicensePlateRecognizerBlock : MediaBlock, IMediaBlock, IDisposable, IMediaBlockInternals

Inheritance

MediaBlock

Implements

IMediaBlock
IMediaBlockInternals

Inherited Members

MediaBlock._isBuilt
MediaBlock._pipeline
MediaBlock._pipelineCtx
MediaBlock.GetPipelineContext()
MediaBlock.SetPipelineContext(BlockPipelineContext)
MediaBlock.SetPipeline(MediaBlocksPipeline)
MediaBlock.Context
MediaBlock.Name
MediaBlock.IsBuilt
MediaBlock.Owner
MediaBlock.Type
MediaBlock.ID
MediaBlock.Input
MediaBlock.Inputs
MediaBlock.Output
MediaBlock.Outputs
MediaBlock.HasInputs
MediaBlock.HasOutputs
MediaBlock.Build()
MediaBlock.CreateElements()
MediaBlock.AddElementsToPipeline()
MediaBlock.RemoveElementsFromPipeline()
MediaBlock.DeepCopy(string)
MediaBlock.Reset()
MediaBlock.ToYAMLBlock()
MediaBlock.ClearPads()
MediaBlock.Dispose(bool)
MediaBlock.Dispose()

Remarks

Recognition runs on a background worker so live video never stalls; the streaming thread only draws the most recent plates onto each frame. The detector and OCR models come from the FastALPR family (MIT).

Constructors

LicensePlateRecognizerBlock(LicensePlateRecognizerSettings)

Initializes a new instance of the VisioForge.Core.MediaBlocks.AI.LicensePlateRecognizerBlock class.

public LicensePlateRecognizerBlock(LicensePlateRecognizerSettings settings)

Parameters

settings LicensePlateRecognizerSettings

The recognizer settings. Must specify valid detector and recognition model paths.

Exceptions

ArgumentNullException

Thrown when settings is null.

Properties

ActiveProvider

Gets the execution provider that the ANPR sessions actually engaged. Valid after the block has been built; reports VisioForge.Core.Types.X.AI.OnnxExecutionProvider.CPU otherwise.

public OnnxExecutionProvider ActiveProvider { get; }

Property Value

OnnxExecutionProvider

DroppedFrameCount

Gets the number of frames that arrived while the background worker was still busy and were therefore skipped for recognition (the live video is unaffected).

public long DroppedFrameCount { get; }

Property Value

long

Input

Gets the primary input pad.

public override MediaBlockPad Input { get; }

Property Value

MediaBlockPad

Inputs

Gets the array of all input pads.

public override MediaBlockPad[] Inputs { get; }

Property Value

MediaBlockPad[]

LastInferenceTimeMs

Gets the wall-clock time, in milliseconds, the most recent recognition took (detection + OCR). It runs on a background thread; use this to tune VisioForge.Core.Types.X.AI.LicensePlateRecognizerSettings.FramesToSkip to the hardware.

public float LastInferenceTimeMs { get; }

Property Value

float

Output

Gets the primary output pad.

public override MediaBlockPad Output { get; }

Property Value

MediaBlockPad

Outputs

Gets the array of all output pads.

public override MediaBlockPad[] Outputs { get; }

Property Value

MediaBlockPad[]

Type

Gets the type of the media block.

public override MediaBlockType Type { get; }

Property Value

MediaBlockType

Methods

Build()

Constructs the internal GStreamer elements and pads for this block.

public override bool Build()

Returns

bool

true if successful, false otherwise.

CleanUp()

Cleans up internal resources, specifically the GStreamer element.

public void CleanUp()

Dispose(bool)

Releases unmanaged and - optionally - managed resources.

protected override void Dispose(bool disposing)

Parameters

disposing bool

true to release both managed and unmanaged resources; false to release only unmanaged resources.

GetCore()

Gets the core GStreamer element wrapped by this block.

public BaseElement GetCore()

Returns

BaseElement

The VisioForge.Core.GStreamer.Base.BaseElement wrapper, or null if not built yet.

GetElement()

Gets the GStreamer element instance.

public Element GetElement()

Returns

Element

The Gst.Element, or null if not built yet.

IMediaBlockInternals.SetContext(MediaBlocksPipeline)

Sets the pipeline context for this block.

void IMediaBlockInternals.SetContext(MediaBlocksPipeline pipeline)

Parameters

pipeline MediaBlocksPipeline

The pipeline.

OnPlateRecognized

Event raised when one or more license plates are recognized in a video frame.

public event EventHandler<LicensePlateRecognizedEventArgs> OnPlateRecognized

Event Type

EventHandler<LicensePlateRecognizedEventArgs>

See Also

MediaBlock
IMediaBlockInternals