Engine

Core generic engine

Engine is a core of any app and organizer of a pipeline. It’s responsible to interact with lower-level instances and at the same time provide simple and user-friendly interface. Engine combines together data (video) capturing, processing and rendering. It’s created for particular Processor. Processor’s constructor or instance is provided to the engine and former initializes and controls state of processor during life-circle of the application. Results of processing and captured image are passed to a Renderer attached to the Engine. Notable feature is fast rescaling of images for processing down to the requested resolution in cases when available camera output is bigger. Engine parameters have an option to limit processed image size. Original video stream can be preserved on request, this is useful when processing cannot handle high resolution images but you still want to render high quality video in your app. All core components: Engine, Processor, and Renderer are generics parametrized by type of processing results and optionally tuning parameters.

Extends

EventEmitterT<EngineEvents>

Extended by

Type Parameters

ResultT

ResultT extends object

Type of processing results

ParamsT

ParamsT extends ProcParams

Type of processor parameters

ProcessorT

ProcessorT extends Processor<ResultT, ParamsT>

Type of processor

Constructors

Constructor

new Engine<ResultT, ParamsT, ProcessorT>(Processor, engineParams?, Source?): Engine<ResultT, ParamsT, ProcessorT>

Constructor

Parameters

Processor

Processor class or instance

ProcessorT | () => ProcessorT

engineParams?

EngineParams

Parameters of the engine

Source?

Video source class or instance

VideoSource | () => VideoSource

Returns

Engine<ResultT, ParamsT, ProcessorT>

Overrides

EventEmitterT.constructor

Properties

engineParams?

protected optional engineParams: EngineParams

Parameters of the engine

processCanvas?

protected optional processCanvas: HTMLCanvasElement

Shallow copy of canvas with video for processors

processor

protected processor: ProcessorT

Processor utilized by the engine

processSize

protected processSize: Size

Size of video for processors

renderers

protected renderers: Renderer<ResultT>[] = []

Renderer attached to the engine

resizeBuffer?

protected optional resizeBuffer: ImageBuffer

Buffer to resize frames

resizeEnabled

protected resizeEnabled: boolean = false

Original stream is resized

streamCanvas?

protected optional streamCanvas: HTMLCanvasElement

Shallow copy of canvas with video for renderers

streamSize

protected streamSize: Size

Size of video for renderers

video

protected video: VideoSource

Video source instance

videoRatio

protected videoRatio: number

Ratio of video stream

Methods

addListener()

addListener<E>(event, listener): this

Adds the listener function to the end of the listeners array

Type Parameters

E

E extends keyof EngineEvents

Parameters

event

E

The name of the event

listener

EngineEvents[E]

The callback function

Returns

this

This EventEmitter

Inherited from

EventEmitterT.addListener

addRenderer()

addRenderer(renderer): Promise<void>

Attach Renderer to the engine

Parameters

renderer

Renderer<ResultT>

Object to be attached

Returns

Promise<void>

emit()

emit<E>(event, …args): boolean

Synchronously calls each of the listeners registered for the event

Type Parameters

E

E extends keyof EngineEvents

Parameters

event

E

The name of the event

args

…Args<EngineEvents[E]>

Arguments passed to the listeners

Returns

boolean

True if the event had listeners, False otherwise

Inherited from

EventEmitterT.emit

enqueue()

protected enqueue(): void

Enqueue the next iteration

Returns

void

eventNames()

eventNames(): (string | symbol)[]

List of emitter’s events

Returns

(string | symbol)[]

List of emitter’s events

Inherited from

EventEmitterT.eventNames

getMaxListeners()

getMaxListeners(): number

Maximum number of listeners per event

Returns

number

Maximum number of listeners per event

Inherited from

EventEmitterT.getMaxListeners

init()

init(procParams): Promise<boolean>

Initialize engine. Sets up processor.

The SDK access token is required parameter that authenticates the user and enables the SDK on the current url. By default, path to required wasm modules provided with SDK packages is the current url. You can change the root path to wasms passing root parameter.

Parameters

procParams

ParamsT

Parameters of the processor

Returns

Promise<boolean>

Status of initialization

iterate()

protected iterate(): Promise<void>

Iterate

Returns

Promise<void>

listenerCount()

listenerCount<E>(event): number

The number of listeners listening to the event

Type Parameters

E

E extends keyof EngineEvents

Parameters

event

E

The name of the event

Returns

number

Number of listeners

Inherited from

EventEmitterT.listenerCount

listeners()

listeners<E>(event): Function[]

Copy of the array of listeners for the event

Type Parameters

E

E extends keyof EngineEvents

Parameters

event

E

The name of the event

Returns

Function[]

Copy of the listeners array

Inherited from

EventEmitterT.listeners

off()

off<E>(event, listener): this

Removes the listener from the listener array for the event

Type Parameters

E

E extends keyof EngineEvents

Parameters

event

E

The name of the event

listener

EngineEvents[E]

The callback function

Returns

this

This EventEmitter

Inherited from

EventEmitterT.off

on()

on<E>(event, listener): this

Adds the listener function to the event

Type Parameters

E

E extends keyof EngineEvents

Parameters

event

E

The name of the event

listener

EngineEvents[E]

The callback function

Returns

this

This EventEmitter

Inherited from

EventEmitterT.on

once()

once<E>(event, listener): this

Adds a one-time listener function for the event

Type Parameters

E

E extends keyof EngineEvents

Parameters

event

E

The name of the event

listener

EngineEvents[E]

The callback function

Returns

this

This EventEmitter

Inherited from

EventEmitterT.once

pause()

pause(): void

Pause pipeline.

Nothing happens if pipeline is not started yet.

Returns

void

prependListener()

prependListener<E>(event, listener): this

Adds the listener function to the beginning of the listeners array

Type Parameters

E

E extends keyof EngineEvents

Parameters

event

E

The name of the event

listener

EngineEvents[E]

The callback function

Returns

this

This EventEmitter

Inherited from

EventEmitterT.prependListener

prependOnceListener()

prependOnceListener<E>(event, listener): this

Adds a one-time listener function to the beginning of the listeners array

Type Parameters

E

E extends keyof EngineEvents

Parameters

event

E

The name of the event

listener

EngineEvents[E]

The callback function

Returns

this

Inherited from

EventEmitterT.prependOnceListener

rawListeners()

rawListeners<E>(event): Function[]

Copy of the array of listeners for the event including wrappers

Type Parameters

E

E extends keyof EngineEvents

Parameters

event

E

The name of the event

Returns

Function[]

Copy of the listeners array

Inherited from

EventEmitterT.rawListeners

removeAllListeners()

removeAllListeners<E>(event?): this

Removes all listeners, or those of the specified event

Type Parameters

E

E extends keyof EngineEvents

Parameters

event?

E

The name of the event

Returns

this

This EventEmitter

Inherited from

EventEmitterT.removeAllListeners

removeListener()

removeListener<E>(event, listener): this

Removes the specified listener from the listener array

Type Parameters

E

E extends keyof EngineEvents

Parameters

event

E

The name of the event

listener

EngineEvents[E]

The callback function

Returns

this

This EventEmitter

Inherited from

EventEmitterT.removeListener

removeRenderer()

removeRenderer(renderer): void

Remove attached Renderer

Parameters

renderer

Renderer<ResultT>

Renderer to be removed

Returns

void

reset()

reset(): void

Reset pipeline

Stops pipeline, resets video capture and processor. After reset one needs to reinitialize video capture calling setup() before pipeline can be started again.

Returns

void

resizeVideo()

protected resizeVideo(size): void

Callback called when video resolution is changed

Parameters

size

Size

Size of the video

Returns

void

setMaxListeners()

setMaxListeners(n): this

Sets maximum number of listeners per event

Parameters

n

number

Maximum number of listeners

Returns

this

This EventEmitter

Inherited from

EventEmitterT.setMaxListeners

setup()

setup(videoParams?): Promise<boolean>

Setup engine. Initializes video capture.

Video capture can be setup by simplified VideoParams opening default front/rear camera with provided resolution. Additional fine-grained MediaStreamConstraints can be passed via opts field providing the most flexible way to setup video stream (for example, by requesting specific deviceId). Stream constraints have higher priority than rest or params. Another options are an external MediaStream allowing custom video sources (e.g. remote stream) or a media file defined by url or FileParams that allows to limit maximum capture size in cases resolution is too big for a device.

Parameters

videoParams?

VideoSourceParams

Parameters of video capture

Returns

Promise<boolean>

Status of initialization

setupProcessor()

protected setupProcessor(procParams): Promise<boolean>

Setup processor

Parameters

procParams

ParamsT

Returns

Promise<boolean>

setupSize()

protected setupSize(size): Promise<void>

Setup video size

Parameters

size

Size

Returns

Promise<void>

setupVideo()

protected setupVideo(videoParams?): Promise<boolean>

Setup video capture

Parameters

videoParams?

VideoSourceParams

Returns

Promise<boolean>

start()

start(): Promise<void>

Start pipeline.

Pipeline can be started only after successful init and setup.

Returns

Promise<void>