104 lines
4 KiB
Markdown
104 lines
4 KiB
Markdown
# desktopCapturer
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> Access information about media sources that can be used to capture audio and
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> video from the desktop using the [`navigator.mediaDevices.getUserMedia`] API.
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Process: [Main](../glossary.md#main-process), [Renderer](../glossary.md#renderer-process)
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The following example shows how to capture video from a desktop window whose
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title is `Electron`:
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```javascript
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// In the renderer process.
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const { desktopCapturer } = require('electron')
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desktopCapturer.getSources({ types: ['window', 'screen'] }).then(async sources => {
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for (const source of sources) {
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if (source.name === 'Electron') {
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try {
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const stream = await navigator.mediaDevices.getUserMedia({
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audio: false,
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video: {
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mandatory: {
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chromeMediaSource: 'desktop',
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chromeMediaSourceId: source.id,
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minWidth: 1280,
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maxWidth: 1280,
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minHeight: 720,
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maxHeight: 720
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}
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}
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})
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handleStream(stream)
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} catch (e) {
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handleError(e)
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}
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return
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}
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}
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})
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function handleStream (stream) {
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const video = document.querySelector('video')
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video.srcObject = stream
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video.onloadedmetadata = (e) => video.play()
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}
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function handleError (e) {
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console.log(e)
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}
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```
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To capture video from a source provided by `desktopCapturer` the constraints
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passed to [`navigator.mediaDevices.getUserMedia`] must include
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`chromeMediaSource: 'desktop'`, and `audio: false`.
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To capture both audio and video from the entire desktop the constraints passed
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to [`navigator.mediaDevices.getUserMedia`] must include `chromeMediaSource: 'desktop'`,
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for both `audio` and `video`, but should not include a `chromeMediaSourceId` constraint.
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```javascript
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const constraints = {
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audio: {
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mandatory: {
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chromeMediaSource: 'desktop'
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}
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},
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video: {
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mandatory: {
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chromeMediaSource: 'desktop'
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}
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}
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}
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```
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## Methods
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The `desktopCapturer` module has the following methods:
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### `desktopCapturer.getSources(options)`
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* `options` Object
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* `types` String[] - An array of Strings that lists the types of desktop sources
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to be captured, available types are `screen` and `window`.
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* `thumbnailSize` [Size](structures/size.md) (optional) - The size that the media source thumbnail
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should be scaled to. Default is `150` x `150`. Set width or height to 0 when you do not need
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the thumbnails. This will save the processing time required for capturing the content of each
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window and screen.
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* `fetchWindowIcons` Boolean (optional) - Set to true to enable fetching window icons. The default
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value is false. When false the appIcon property of the sources return null. Same if a source has
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the type screen.
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Returns `Promise<DesktopCapturerSource[]>` - Resolves with an array of [`DesktopCapturerSource`](structures/desktop-capturer-source.md) objects, each `DesktopCapturerSource` represents a screen or an individual window that can be captured.
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**Note** Capturing the screen contents requires user consent on macOS 10.15 Catalina or higher,
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which can detected by [`systemPreferences.getMediaAccessStatus`].
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[`navigator.mediaDevices.getUserMedia`]: https://developer.mozilla.org/en/docs/Web/API/MediaDevices/getUserMedia
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[`systemPreferences.getMediaAccessStatus`]: system-preferences.md#systempreferencesgetmediaaccessstatusmediatype-macos
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## Caveats
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`navigator.mediaDevices.getUserMedia` does not work on macOS for audio capture due to a fundamental limitation whereby apps that want to access the system's audio require a [signed kernel extension](https://developer.apple.com/library/archive/documentation/Security/Conceptual/System_Integrity_Protection_Guide/KernelExtensions/KernelExtensions.html). Chromium, and by extension Electron, does not provide this.
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It is possible to circumvent this limitation by capturing system audio with another macOS app like Soundflower and passing it through a virtual audio input device. This virtual device can then be queried with `navigator.mediaDevices.getUserMedia`.
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