# Remove backgrounds with an alpha channel

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> The code on this page works with either the **default UI** or the **custom UI**.

Meeting hosts who hold a raw streaming token can enable alpha channel mode, which requests that Zoom send both the
original video data and a mask demarking the edge of a participant's body. The SDK can then use the alpha mask and
raw data to remove the participant's background and render meeting participants natively in the host's virtual world.

## Add new methods

Add a new method to the `IMeetingVideoCtrlEvent` class.

```cpp
/// \brief Callback event of alpha channel mode changes.
/// \param isAlphaModeOn true means is in alpha channel mode.
virtual void onVideoAlphaChannelStatusChanged(bool isAlphaModeOn) = 0;
```

This callback is triggered when alpha channel mode is turned on.

Add these methods to the `IMeetingVideoController` class.

```cpp
/// \brief Determine if can enable alpha channel mode.
/// \return true means can enable.
virtual bool CanEnableAlphaChannelMode() = 0;

/// \brief Enable or disable alpha channel mode.
/// \param enable TRUE indicates to enable alpha channel mode. Otherwise, disable it.
/// \return If the function succeeds, the return value is SDKErr_Success.
///Otherwise, the function failed. To get extended error information, see SDKError enum.
virtual SDKError EnableAlphaChannelMode(bool enable) = 0;

/// \brief Determine if is in alpha channel mode.
/// \return TRUE indicates is in alpha channel mode.
virtual bool IsAlphaChannelModeEnabled() = 0;
```

## Enable alpha channel mode

Before enabling the alpha channel, call `canEnableAlphaChannelMode` to check whether the alpha channel mode is
enabled. To enable or disable the alpha channel, call `EnableAlphaChannelMode`.

Add a new method to the `YUVRawDataI420` class.

```cpp
/// \brief Get video alpha mask data buffer.
/// \return buffer address if alpha data exists, otherwise NULL.
virtual char* GetAlphaBuffer() = 0;

/// \brief Get the alpha buffer length.
/// \return The length of alpha data.
virtual unsigned int GetAlphaBufferLen() = 0;
```

The raw data will have two more values after performing these steps: `GetAlphaBuffer` for the alpha data buffer,
and another, `GetAlphaBufferLen`, for the alpha data buffer length.

Now that you've received the data, [edit the raw data](/docs/meeting-sdk/windows/custom-ui/advanced-features/raw-data).

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