Relaks Media Capture

A reusable library for capturing video, audio, and images in a web browser. Designed to be used with Relaks.

• Installation
• Usage
• Options
• Properties
• Methods
• Events
• Examples

Installation

npm --save-dev install relaks-media-capture

Usage

import RelaksMediaCapture from 'relaks-media-capture';
 
class VideoDialogBox extends AsyncComponent {
  constructor(props) {
    super(props);
    let options = {
      video: true,
      audio: true,
      watchVolume: true,
    };
    this.capture = new RelaksMediaCapture(options);
  }
 
  async renderAsync(meanwhile) {
    meanwhile.delay(50, 50);
    let props = {
      onStart: this.handleStart,
      onStop: this.handleStop,
      onPause: this.handlePause,
      onResume: this.handleResume,
      onClear: this.handleClear,
      onChoose: this.handleChoose,
      onAccept: this.handleAccept,
      onCancel: this.handleCancel,
    };
    this.capture.activate();
    do {
      props.status = this.capture.status;
      props.devices = this.capture.devices;
      props.chosenDeviceID = this.capture.chosenDeviceID;
      props.liveVideo = this.capture.liveVideo;
      props.duration = this.capture.duration;
      props.volume = this.capture.volume;
      props.capturedImage = this.capture.capturedImage;
      props.capturedVideo = this.capture.capturedVideo;
      meanwhile.show(<VideoDialogBoxSync {...props} />);
      await this.capture.change();
    } while (this.capture.active);
    return <VideoDialogBoxSync {...props} />;
  }
}

Options

• audio
• audioBitsPerSecond
• audioMIMEType
• captureImageOnly
• chooseNewDevice
• deactivationDelay
• imageMIMEType
• preferredDevice
• segmentDuration
• silent
• video
• videoBitsPerSecond
• videoMIMEType
• watchVolume

audio

A boolean indicating whether audio is desired.

Default value: true.

audioBitsPerSecond

The desired audio bitrate.

Default value: 128000

audioMIMEType

The desired audio type. Due to licensing cost, it's unlikely that anything other than the open source WebM would be available.

Default value: "audio/webm"

captureImageOnly

Whether the desired result is an image rather than a video. When it's set, calling snap() will change the status to "captured".

Default value: false

chooseNewDevice

Whether a new device should be automatically chosen as the input.

Default value: true

imageMIMEType

The desired audio type.

Default value: "image/jpeg"

preferredDevice

A text string indicating the preferred input device. If the device label contains the text, it'll be chosen.

Default value: "front"

segmentDuration

Duration of a video segment, in millisecond, that the MediaRecorder should yield as soon as that amount of data becomes available. This allows a video to be uploaded in chunks as it's being recorded.

When it's set, the media capture object will emit the chunk event periodically. It'll emit the end event when capturing ends.

Default value: undefined

silent

Whether errors get sent to the development console.

Default value: false.

video

A boolean indicating whether video is desired.

Default value: true

videoBitsPerSecond

The desired video bitrate.

Default value: 2500000

videoMIMEType

The desired video type. Due to licensing cost, it's unlikely that anything other than the open source WebM would be available.

Default value: "video/webm"

watchVolume

A boolean indicating whether audio volume should be monitored.

Default value: false

Properties

• active
• capturedImage
• capturedAudio
• capturedVideo
• chosenDeviceID
• devices
• duration
• lastError
• liveAudio
• liveVideo
• status
• volume

active

A boolean indicating whether the media capture object is active.

capturedImage

An object holding properties of the captured image, with the following properties:

• blob - blob containing the image data
• url - URL to the blob
• width - Width of the image
• height - height of the image

The URL will be revoked when deactivate() is called. It should only be used while the media capture object is active.

capturedAudio

An object holding properties of the captured audio, with the following properties:

• blob - blob containing the audio data
• url - URL to the blob

The URL will be revoked when deactivate() is called. It should only be used while the media capture object is active.

capturedVideo

• blob - blob containing the video data
• url - URL to the blob
• width - width of the image
• height - height of the image

The URL will be revoked when deactivate() is called. It should only be used while the media capture object is active.

chosenDeviceID

ID of the currently chosen camera.

devices

An array containing objects describing available input devices, each with the following properties:

• id - the device's ID (a string)
• label - the device's name

duration

Duration of the captured video/audio, in millisecond. undefined initially.

lastError

The last error encountered.

liveAudio

An object representing the input from the microphone, with the following properties:

• stream - an instance of MediaStream

It's only available when audio is true and video is false.

liveVideo

An object representing the input from the camera, with the following properties:

• stream - an instance of MediaStream
• height - the height of the video
• width - the width of the video

It's available when video is true.

height and width will swap when the user rotates a phone or tablet.

status

One of the following:

• "acquiring" - in the process of acquiring a camera
• "denied" - permission to use camera was denied
• "initiating" - permission has been granted and the camera is about to become available
• "previewing" - camera input is available
• "capturing" - video/audio capturing is happening
• "paused" - Video/audio capturing has been paused
• "captured" - a video, audio, or image has been captured

volume

A number between 0 and 100 indicating the strength of audio coming from the microphone.

It's present only when watchVolume is true.

Methods

Event listeners:

• addEventListener()
• removeEventListener()
• waitForEvent()

Activation

• activate()
• deactivate()

Video/audio capture:

• pause()
• resume()
• start()
• stop()

Image capture:

• snap()

Others:

• change()
• choose()
• clear()

addEventListener()

function addEventListener(type: string, handler: function, beginning?:boolean): void

Add an event listener to the route manager. handler will be called whenever events of type occur. When beginning is true, the listener will be place before any existing listeners. Otherwise it's added at the end of the list.

Inherited from relaks-event-emitter.

removeEventListener()

function removeEventListener(type: string, handler: function): void

Remove an event listener from the route manager. handler and type must match what was given to addEventListener().

Inherited from relaks-event-emitter.

waitForEvent()

async function waitForEvent(type: string): Event

Return a promise that is fulfilled when an event of the specified type occurs.

Inherited from relaks-event-emitter.

activate()

function activate(): void

Activate the media capture object.

deactivate()

function deactivate(): void

Deactivate the media capture object.

pause()

function pause(): void

Pause capturing. status will change to "pause".

resume()

function resume(): void

Resume capturing. status will become "capturing" again.

start()

function start(): void

Start capturing video and/or audio. status will change to "capturing".

stop()

function stop(): void

Stop capturing. status will change to "captured" soon afterward.

snap()

function snap(): void

Take a snapshot of the camera input. The result will be stored in capturedImage.

status will become "captured" afterward if captureImageOnly is true.

change()

async function change(): Event

Wait for a change event to occur.

choose()

async function choose(id: String): void

Choose the camera or mic with the specified ID as the recording device.

clear()

function clear(): void

Clear capturedVideo, capturedAudio, and capturedImage. Return to previewing.

Events

• change
• chunk
• end

change

The change event is emitted after a property of media capture object has changed.

Properties:

• propagationStopped - whether stopImmediatePropagation() was called
• target - media capture object
• type - "change"

Methods:

• stopImmediatePropagation() - stop other listeners from receiving the event

chunk

The chunk event is emitted when a chunk of data become available. Only occurs when segmentDuration is set.

Properties:

• blob - a Blob containing data of a video/audio segment
• propagationStopped - whether stopImmediatePropagation() was called
• target - media capture object
• type - "change"

Methods:

• stopImmediatePropagation() - stop other listeners from receiving the event

end

The end event is emitted when video recording has come to an end, after the final chunk event. Only occurs when segmentDuration is set.

Properties:

• propagationStopped - whether stopImmediatePropagation() was called
• target - media capture object
• type - "change"

Methods:

• stopImmediatePropagation() - stop other listeners from receiving the event

Examples

• Media Capture Example