# Core features

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The Video SDK for Android lets you programmatically control user video during a session: check video status, start video, stop video, and render one or many users. For switching, mirroring, rotating, and other per-device camera operations, see [Camera controls](/docs/video-sdk/android/video/camera-controls/).

> **Camera permission required.**
>
> Before using video, your app must request the `CAMERA` runtime permission. For the runtime-permission flow, see the [Android permissions overview](https://developer.android.com/guide/topics/permissions/overview).

## Check whether video is on

To check whether a user has their video on, call `isOn` on `videoStatus` to get a boolean response indicating whether the user has their video on or not in the session.

```kotlin
val isVideoOn = user.videoCanvas.videoStatus.isOn
```

```java
boolean isVideoOn = user.getVideoCanvas().getVideoStatus().isOn();
```

## Start video

Start video by calling `startVideo()` on the `VideoHelper`. Be sure your app has been granted `CAMERA` permission before calling or the SDK can't capture from the camera.

```kotlin
val videoHelper = ZoomVideoSDK.getInstance().videoHelper
videoHelper.startVideo()
```

```java
ZoomVideoSDKVideoHelper videoHelper = ZoomVideoSDK.getInstance().getVideoHelper();
videoHelper.startVideo();
```

## Stop video

Stop video by calling `stopVideo()` on the `VideoHelper`.

```kotlin
ZoomVideoSDK.getInstance().videoHelper.stopVideo()
```

```java
ZoomVideoSDK.getInstance().getVideoHelper().stopVideo();
```

## Render a user's video

To render a user's video, get the user's `ZoomVideoSDKVideoCanvas` and subscribe a `ZoomVideoSDKVideoView` to it. The view can be created programmatically or declared in XML.

```kotlin
val videoView = ZoomVideoSDKVideoView(this)
val canvas = user.videoCanvas
canvas.subscribe(videoView, ZoomVideoSDKVideoAspect.ZoomVideoSDKVideoAspect_Original)
```

```java
ZoomVideoSDKVideoView videoView = new ZoomVideoSDKVideoView(this);
ZoomVideoSDKVideoCanvas canvas = user.getVideoCanvas();
canvas.subscribe(videoView, ZoomVideoSDKVideoAspect.ZoomVideoSDKVideoAspect_Original);
```

```xml
<us.zoom.sdk.ZoomVideoSDKVideoView
    android:id="@+id/video_view"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />
```

The `aspect` parameter controls how Zoom fits the video into the view.

| Type                                  | Description                                                                              |
| ------------------------------------- | ---------------------------------------------------------------------------------------- |
| `ZoomVideoSDKVideoAspect_Original`    | Display video without any modifications.                                                 |
| `ZoomVideoSDKVideoAspect_Full_Filled` | Stretch the video to fill the canvas.                                                    |
| `ZoomVideoSDKVideoAspect_LetterBox`   | Add black bars (top/bottom or left/right) so the full frame is visible without cropping. |
| `ZoomVideoSDKVideoAspect_PanAndScan`  | Crop the frame to fill the canvas without bars.                                          |

For more on choosing an aspect mode and on responsive layouts, see [Aspect ration and orientation](/docs/video-sdk/android/video/best-practices/#aspect-ratio-and-orientation).

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

When a user leaves the session, or when you want to recycle a `ZoomVideoSDKVideoView` for a different user, unsubscribe from the canvas.

```kotlin
videoCanvas.unsubscribe(videoView)
```

```java
videoCanvas.unsubscribe(videoView);
```

## Render multiple users

To render multiple users at once (gallery view), iterate over the users in the session and subscribe a `ZoomVideoSDKVideoView` for each. Respond to `onUserJoin` to add new users as they enter, and `onUserLeave` to unsubscribe.

```kotlin
override fun onUserJoin(userHelper: ZoomVideoSDKUserHelper, userList: MutableList<ZoomVideoSDKUser>) {
    userList.forEach { user ->
        val videoView = ZoomVideoSDKVideoView(this@MyActivity)
        user.videoCanvas.subscribe(videoView, ZoomVideoSDKVideoAspect.ZoomVideoSDKVideoAspect_Original)
        // add videoView to your gallery container
    }
}

override fun onUserLeave(userHelper: ZoomVideoSDKUserHelper, userList: MutableList<ZoomVideoSDKUser>) {
    userList.forEach { user ->
        // unsubscribe and remove the corresponding view from the container
    }
}
```

```java
@Override
public void onUserJoin(ZoomVideoSDKUserHelper userHelper, List<ZoomVideoSDKUser> userList) {
    for (ZoomVideoSDKUser user : userList) {
        ZoomVideoSDKVideoView videoView = new ZoomVideoSDKVideoView(this);
        user.getVideoCanvas().subscribe(videoView, ZoomVideoSDKVideoAspect.ZoomVideoSDKVideoAspect_Original);
        // add videoView to your gallery container
    }
}

@Override
public void onUserLeave(ZoomVideoSDKUserHelper userHelper, List<ZoomVideoSDKUser> userList) {
    for (ZoomVideoSDKUser user : userList) {
        // unsubscribe and remove the corresponding view from the container
    }
}
```

For grid layout, density recommendations, and pagination guidance, see [Layout and density](/docs/video-sdk/android/video/best-practices/#layout-and-density).