desktopCapturer

desktopCapturer

访问有关可用于使用 navigator.mediaDevices.getUserMedia API 从桌面捕获音频和视频的媒体源的信息。

¥Access information about media sources that can be used to capture audio and video from the desktop using the navigator.mediaDevices.getUserMedia API.

进程：主进程

¥Process: Main

以下示例显示如何从标题为 Electron 的桌面窗口捕获视频：

¥The following example shows how to capture video from a desktop window whose title is Electron:

// In the main process.
const { BrowserWindow, desktopCapturer } = require('electron')

const mainWindow = new BrowserWindow()

desktopCapturer.getSources({ types: ['window', 'screen'] }).then(async sources => {
  for (const source of sources) {
    if (source.name === 'Electron') {
      mainWindow.webContents.send('SET_SOURCE', source.id)
      return
    }
  }
})

// In the preload script.
const { ipcRenderer } = require('electron')

ipcRenderer.on('SET_SOURCE', async (event, sourceId) => {
  try {
    const stream = await navigator.mediaDevices.getUserMedia({
      audio: false,
      video: {
        mandatory: {
          chromeMediaSource: 'desktop',
          chromeMediaSourceId: sourceId,
          minWidth: 1280,
          maxWidth: 1280,
          minHeight: 720,
          maxHeight: 720
        }
      }
    })
    handleStream(stream)
  } catch (e) {
    handleError(e)
  }
})

function handleStream (stream) {
  const video = document.querySelector('video')
  video.srcObject = stream
  video.onloadedmetadata = (e) => video.play()
}

function handleError (e) {
  console.log(e)
}

要从 desktopCapturer 提供的源捕获视频，传递给 navigator.mediaDevices.getUserMedia 的约束必须包括 chromeMediaSource: 'desktop' 和 audio: false。

¥To capture video from a source provided by desktopCapturer the constraints passed to navigator.mediaDevices.getUserMedia must include chromeMediaSource: 'desktop', and audio: false.

要从整个桌面捕获音频和视频，传递给 navigator.mediaDevices.getUserMedia 的约束必须包括 chromeMediaSource: 'desktop'（对于 audio 和 video），但不应包括 chromeMediaSourceId 约束。

¥To capture both audio and video from the entire desktop the constraints passed to navigator.mediaDevices.getUserMedia must include chromeMediaSource: 'desktop', for both audio and video, but should not include a chromeMediaSourceId constraint.

const constraints = {
  audio: {
    mandatory: {
      chromeMediaSource: 'desktop'
    }
  },
  video: {
    mandatory: {
      chromeMediaSource: 'desktop'
    }
  }
}

方法

¥Methods

desktopCapturer 模块有以下方法：

¥The desktopCapturer module has the following methods:

desktopCapturer.getSources(options)

• options 对象

  ¥options Object

  • types 字符串[] - 列出要捕获的桌面源类型的字符串数组，可用类型可以是 screen 和 window。

    ¥types string[] - An array of strings that lists the types of desktop sources to be captured, available types can be screen and window.

  • thumbnailSize 尺寸（可选） - 媒体源缩略图应缩放到的大小。默认值为 150 x 150。当不需要缩略图时，将宽度或高度设置为 0。这将节省捕获每个窗口和屏幕的内容所需的处理时间。

    ¥thumbnailSize Size (optional) - The size that the media source thumbnail should be scaled to. Default is 150 x 150. Set width or height to 0 when you do not need the thumbnails. This will save the processing time required for capturing the content of each window and screen.

  • fetchWindowIcons 布尔值（可选） - 设置为 true 以启用获取窗口图标。默认值为 false。当 false 时，源的 appIcon 属性返回 null。如果源具有类型屏幕，则相同。

    ¥fetchWindowIcons boolean (optional) - Set to true to enable fetching window icons. The default value is false. When false the appIcon property of the sources return null. Same if a source has the type screen.

返回 Promise<DesktopCapturerSource[]> - 使用 DesktopCapturerSource 对象数组进行解析，每个 DesktopCapturerSource 代表一个屏幕或可以捕获的单个窗口。

¥Returns Promise<DesktopCapturerSource[]> - Resolves with an array of DesktopCapturerSource objects, each DesktopCapturerSource represents a screen or an individual window that can be captured.

注意 在 macOS 10.15 Catalina 或更高版本上捕获屏幕内容需要用户同意，这可以被 systemPreferences.getMediaAccessStatus 检测到。

¥Note Capturing the screen contents requires user consent on macOS 10.15 Catalina or higher, which can detected by systemPreferences.getMediaAccessStatus.

注意事项

¥Caveats

navigator.mediaDevices.getUserMedia 无法在 macOS 上进行音频捕获，因为存在一个基本限制，即想要访问系统音频的应用需要 签名的内核扩展。Chromium 以及 Electron 并没有提供这一点。

¥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. Chromium, and by extension Electron, does not provide this.

可以通过使用 Soundflower 等其他 macOS 应用捕获系统音频并将其通过虚拟音频输入设备传递来规避此限制。然后可以使用 navigator.mediaDevices.getUserMedia 查询该虚拟设备。

¥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.