# Core features

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The Video SDK for macOS lets you control user video during a session: check video status, start video, stop video, and render a user's video. For per-device camera operations (switching, mirroring, rotating, pan/tilt/zoom), see [Camera controls](/docs/video-sdk/macos/video/camera-controls/).

> Prior to using video controls, you must **request permission to use the camera**. For details, see [Requesting Authorization for Media Capture on macOS](https://developer.apple.com/documentation/avfoundation/cameras_and_media_capture/requesting_authorization_for_media_capture_on_macos?language=objc).

## Start video

If the user's video is not already enabled, start video using `startVideo`, provided by the `ZMVideoSDKVideoHelper`.

```swift
// Get the ZMVideoSDKVideoHelper to perform video actions.
if let videoHelper = ZMVideoSDK.shared()?.getVideoHelper() {
    // Start local user's video.
    videoHelper.startVideo()
}
```

```objectivec
// Get the ZMVideoSDKVideoHelper to perform video actions.
ZMVideoSDKVideoHelper *videoHelper = [[ZMVideoSDK sharedVideoSDK] getVideoHelper];
if (videoHelper) {
    // Start local user's video.
    [videoHelper startVideo];
}
```

## Stop video

To stop displaying the video of the user, use `stopVideo`.

```swift
// Get the ZMVideoSDKVideoHelper to perform video actions.
if let videoHelper = ZMVideoSDK.shared()?.getVideoHelper() {
    // Stop local user's video.
    videoHelper.stopVideo()
}
```

```objectivec
// Get the ZMVideoSDKVideoHelper to perform video actions.
ZMVideoSDKVideoHelper *videoHelper = [[ZMVideoSDK sharedVideoSDK] getVideoHelper];
if (videoHelper) {
    // Stop local user's video.
    [videoHelper stopVideo];
}
```

## Render a user's video

To display a user's video, get their `ZMVideoSDKVideoCanvas` and subscribe an `NSView` to it. Retrieve each `ZMVideoSDKUser` as they join the session, then subscribe a view to render their stream.

### Retrieve user

The `ZMVideoSDKUserHelper` helps with retrieval of user information. For more details on user management, see [Sessions](/docs/video-sdk/macos/sessions/).

To be notified when users join a session, use `onUserJoin` within `ZMVideoSDKDelegate`.

```swift
func onUserJoin(_ userHelper: ZMVideoSDKUserHelper!, userList userArray: [ZMVideoSDKUser]!) {
    // userArray contains the new users.
    // Use helper to perform actions on a user.
    if let userArray = userArray {
        for user in userArray {
            print(user)
        }
    }
}
```

```objectivec
- (void)onUserJoin:(ZMVideoSDKUserHelper*)userHelper userList:(NSArray<ZMVideoSDKUser >)userArray {
    // userArray contains the new users.
    // Use helper to perform actions on a user.
    for (int i = 0; i < userArray.count; i++) {
        NSLog(@"%@", userArray[i]);
    }
}
```

### Render a user's video into a view

Get the user's `ZMVideoSDKVideoCanvas` and subscribe an `NSView` to it with `subscribeWithView`, passing an aspect mode and resolution.

```swift
if let canvas = user.getVideoCanvas() {
    canvas.subscribe(with: yourView, aspectMode: .panAndScan, resolution: .auto)
}
```

```objectivec
ZMVideoSDKVideoCanvas *canvas = [user getVideoCanvas];
[canvas subscribeWithView:yourView aspectMode:ZMVideoSDKVideoAspect_PanAndScan resolution:ZMVideoSDKResolution_Auto];
```

The aspect mode controls how Zoom fits the video into the view.

| Type                                | Description                                                                        |
| ----------------------------------- | ---------------------------------------------------------------------------------- |
| `ZMVideoSDKVideoAspect_Original`    | Display the video without any modifications.                                       |
| `ZMVideoSDKVideoAspect_Full_Filled` | Stretch the video to fill the view.                                                |
| `ZMVideoSDKVideoAspect_LetterBox`   | Add bars (top/bottom or left/right) so the full frame is visible without cropping. |
| `ZMVideoSDKVideoAspect_PanAndScan`  | Crop the frame to fill the view without bars.                                      |

To render multiple users at once (gallery view), subscribe a view for each user in `onUserJoin` and unsubscribe in `onUserLeave`.

### Remove a user's video from a view

When a user leaves the session, or when you recycle a view for a different user, unsubscribe with `unSubscribeWithView`.

```swift
user.getVideoCanvas()?.unSubscribe(with: yourView)
```

```objectivec
[[user getVideoCanvas] unSubscribeWithView:yourView];
```

For custom rendering from raw YUV frames instead of an `NSView`, see [Receive raw video data](/docs/video-sdk/macos/raw-data/receive-raw-data/#receive-raw-video-data) to subscribe to the user's video pipe. For sending or pre-processing video, see [Send raw data](/docs/video-sdk/macos/raw-data/send-raw-data/).

## Check the video status of a user

You can control video on a per-user basis. First check the current video status of the user.

```swift
// Get videoStatus for user.
let videoStatus = user.videoStatus()
// Check if user's video is on.
let isVideoOn = user.getVideoPipe().getVideoStatus().isOn()
```

```objectivec
// Get videoStatus for user.
ZMVideoSDKVideoStatus *videoStatus = [user videoStatus];
// Check if user's video is on.
BOOL isVideoOn = [[[user getVideoPipe] getVideoStatus] isOn];
```

To react to video status changes for all users, implement [`onUserVideoStatusChanged`](/docs/video-sdk/macos/video/video-events/#user-video-status).