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# Motion Tracking

In Android {{ androidPVersionNumber }}, camera devices can advertise
[motion tracking capability](https://developer.android.com/reference/android/hardware/camera2/CameraMetadata#REQUEST_AVAILABLE_CAPABILITIES_MOTION_TRACKING){: .external}.
Cameras that support this feature do not produce motion tracking data itself,
but instead are used by ARCore or an image-stabilization algorithm along with
other sensors for scene analysis. To support this feature, devices must support
[`CONTROL_CAPTURE_INTENT_MOTION_TRACKING`](https://developer.android.com/reference/android/hardware/camera2/CameraMetadata#CONTROL_CAPTURE_INTENT_MOTION_TRACKING){: .external}.
If this intent is part of the capture request, the camera must limit the
exposure time to a maximum of 20 milliseconds to reduce motion blur.

## Examples and source

A reference motion tracking implementation on the HAL side is available as part
of the
[Camera HAL](https://android.googlesource.com/platform/hardware/qcom/camera/+/master/msm8998/QCamera2/HAL3/QCamera3HWI.cpp){: .external}.

## Implementation

To enable motion tracking on a camera device, make sure:

+   The
    [`ANDROID_REQUEST_AVAILABLE_CAPABILITIES_MOTION_TRACKING`](https://android.googlesource.com/platform/hardware/interfaces/+/master/camera/metadata/3.3/types.hal#231){: .external}
    capability is enabled.
+   The
    [`ANDROID_CONTROL_CAPTURE_INTENT_MOTION_TRACKING`](https://android.googlesource.com/platform/hardware/interfaces/+/master/camera/metadata/3.3/types.hal#207){: .external}
    intent is supported and when included in a capture request limits the camera
    exposure time to a maximum of 20 milliseconds.
+   Lens calibration data from the following list is accurately reported in the
    static information and dynamic metadata fields:

    +   [`ANDROID_LENS_POSE_ROTATION`](https://android.googlesource.com/platform/hardware/interfaces/+/master/camera/metadata/3.2/types.hal#747){: .external}  
    +   [`ANDROID_LENS_POSE_TRANSLATION`](https://android.googlesource.com/platform/hardware/interfaces/+/master/camera/metadata/3.2/types.hal#753){: .external}  
    +   [`ANDROID_LENS_INTRINSIC_CALIBRATION`](https://android.googlesource.com/platform/hardware/interfaces/+/master/camera/metadata/3.2/types.hal#773){: .external}  
    +   [`ANDROID_LENS_RADIAL_DISTORTION`](https://android.googlesource.com/platform/hardware/interfaces/+/master/camera/metadata/3.2/types.hal#780){: .external}  
    +   [`ANDROID_LENS_POSE_REFERENCE`](https://android.googlesource.com/platform/hardware/interfaces/+/master/camera/metadata/3.3/types.hal#79){: .external}  

## Validation

Camera devices supporting the motion tracking feature must pass the
[camera CTS tests](/compatibility/cts/camera-hal#cts_tests).