Camera2 API AutoFocus with Samsung S5

Question

I'm working with the new Camera2 API on a Samsung S5. The supported hardware level this device is reporting is LEGACY, which is fine.

However, I cannot seem to be able to auto-focus on this device. The request to trigger auto-focus looks like this:

previewRequestBuilder.set(CaptureRequest.CONTROL_AF_MODE, CaptureRequest.CONTROL_AF_MODE_AUTO);
previewRequestBuilder.set(CaptureRequest.CONTROL_AF_TRIGGER, CaptureRequest.CONTROL_AF_TRIGGER_START);
state = STATE_PREVIEW;
try {
  captureSession.setRepeatingRequest(previewRequestBuilder.build(), captureCallback, backgroundHandler);
} catch (CameraAccessException e) {
  e.printStackTrace();
}

After the request is sent, the result of the request is always CONTROL_AF_STATE_ACTIVE_SCAN and occasionally CONTROL_AF_STATE_NOT_FOCUSED_LOCKED.

The strange thing is that, when the state is CONTROL_AF_STATE_NOT_FOCUSED_LOCKED, the auto-focus goes back into the CONTROL_AF_STATE_ACTIVE_SCAN state for a while and then back to CONTROL_AF_STATE_NOT_FOCUSED_LOCKED, resulting in a infinite focus loop. According to the docs, when state is CONTROL_AF_STATE_NOT_FOCUSED_LOCKED...

The lens will remain stationary until the AF mode (android.control.afMode) is changed or a new AF trigger is sent to the camera device (android.control.afTrigger).

I'm wondering if this discrepancy is because of the fact that the hardware level is LEGACY and that I should go back to using the deprecated Camera API, but that seems crazy for such a prevalent feature such as auto focus.

Is there any reccomendations how how to treat devices that are reporting LEGACY?

Answer 1

I branched form google's Camera2Basic example and changed it to use CaptureRequest.CONTROL_AF_MODE_AUTO instead of CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE

You can take the project from git and test it - https://github.com/pinhassi/android-Camera2Basic

Or just add this to Camera2BasicFragment:

private static final long LOCK_FOCUS_DELAY_ON_FOCUSED = 5000;
private static final long LOCK_FOCUS_DELAY_ON_UNFOCUSED = 1000;

private Integer mLastAfState = null;
private Handler mUiHandler = new Handler(); // UI handler
private Runnable mLockAutoFocusRunnable = new Runnable() {

    @Override
    public void run() {
        lockAutoFocus();
    }
};


public void lockAutoFocus() {
    try {
        // This is how to tell the camera to lock focus.
        mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AF_TRIGGER, CameraMetadata.CONTROL_AF_TRIGGER_START);
        CaptureRequest captureRequest = mPreviewRequestBuilder.build();
        mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AF_TRIGGER, null); // prevent CONTROL_AF_TRIGGER_START from calling over and over again
        mCaptureSession.capture(captureRequest, mCaptureCallback, mBackgroundHandler);
    } catch (CameraAccessException e) {
        e.printStackTrace();
    }
}


/**
 *
 * @return
 */
private float getMinimumFocusDistance() {
    if (mCameraId == null)
        return 0;

    Float minimumLens = null;
    try {
        CameraManager manager = (CameraManager) getActivity().getSystemService(Context.CAMERA_SERVICE);
        CameraCharacteristics c = manager.getCameraCharacteristics(mCameraId);
        minimumLens = c.get(CameraCharacteristics.LENS_INFO_MINIMUM_FOCUS_DISTANCE);
    } catch (Exception e) {
        Log.e(TAG, "isHardwareLevelSupported Error", e);
    }
    if (minimumLens != null)
        return minimumLens;
    return 0;
}

/**
 *
 * @return
 */
private boolean isAutoFocusSupported() {
    return  isHardwareLevelSupported(CameraCharacteristics.INFO_SUPPORTED_HARDWARE_LEVEL_LEGACY) || getMinimumFocusDistance() > 0;
}

// Returns true if the device supports the required hardware level, or better.
@TargetApi(Build.VERSION_CODES.LOLLIPOP)
private boolean isHardwareLevelSupported(int requiredLevel) {
    boolean res = false;
    if (mCameraId == null)
        return res;
    try {
        CameraManager manager = (CameraManager) getActivity().getSystemService(Context.CAMERA_SERVICE);
        CameraCharacteristics cameraCharacteristics = manager.getCameraCharacteristics(mCameraId);

        int deviceLevel = cameraCharacteristics.get(CameraCharacteristics.INFO_SUPPORTED_HARDWARE_LEVEL);
        switch (deviceLevel) {
            case CameraCharacteristics.INFO_SUPPORTED_HARDWARE_LEVEL_3:
                Log.d(TAG, "Camera support level: INFO_SUPPORTED_HARDWARE_LEVEL_3");
                break;
            case CameraCharacteristics.INFO_SUPPORTED_HARDWARE_LEVEL_FULL:
                Log.d(TAG, "Camera support level: INFO_SUPPORTED_HARDWARE_LEVEL_FULL");
                break;
            case CameraCharacteristics.INFO_SUPPORTED_HARDWARE_LEVEL_LEGACY:
                Log.d(TAG, "Camera support level: INFO_SUPPORTED_HARDWARE_LEVEL_LEGACY");
                break;
            case CameraCharacteristics.INFO_SUPPORTED_HARDWARE_LEVEL_LIMITED:
                Log.d(TAG, "Camera support level: INFO_SUPPORTED_HARDWARE_LEVEL_LIMITED");
                break;
            default:
                Log.d(TAG, "Unknown INFO_SUPPORTED_HARDWARE_LEVEL: " + deviceLevel);
                break;
        }


        if (deviceLevel == CameraCharacteristics.INFO_SUPPORTED_HARDWARE_LEVEL_LEGACY) {
            res = requiredLevel == deviceLevel;
        } else {
            // deviceLevel is not LEGACY, can use numerical sort
            res = requiredLevel <= deviceLevel;
        }

    } catch (Exception e) {
        Log.e(TAG, "isHardwareLevelSupported Error", e);
    }
    return res;
}

Then, add to STATE_PREVIEW block:

        case STATE_PREVIEW: {

            // We have nothing to do when the camera preview is working normally.
            // TODO: handle auto focus
            Integer afState = result.get(CaptureResult.CONTROL_AF_STATE);
            if (afState != null && !afState.equals(mLastAfState)) {
                switch (afState) {
                    case CaptureResult.CONTROL_AF_STATE_INACTIVE:
                        Log.d(TAG, "CaptureResult.CONTROL_AF_STATE_INACTIVE");
                        lockAutoFocus();
                        break;
                    case CaptureResult.CONTROL_AF_STATE_ACTIVE_SCAN:
                        Log.d(TAG, "CaptureResult.CONTROL_AF_STATE_ACTIVE_SCAN");
                        break;
                    case CaptureResult.CONTROL_AF_STATE_FOCUSED_LOCKED:
                        Log.d(TAG, "CaptureResult.CONTROL_AF_STATE_FOCUSED_LOCKED");
                        mUiHandler.removeCallbacks(mLockAutoFocusRunnable);
                        mUiHandler.postDelayed(mLockAutoFocusRunnable, LOCK_FOCUS_DELAY_ON_FOCUSED);
                        break;
                    case CaptureResult.CONTROL_AF_STATE_NOT_FOCUSED_LOCKED:
                        mUiHandler.removeCallbacks(mLockAutoFocusRunnable);
                        mUiHandler.postDelayed(mLockAutoFocusRunnable, LOCK_FOCUS_DELAY_ON_UNFOCUSED);
                        Log.d(TAG, "CaptureResult.CONTROL_AF_STATE_NOT_FOCUSED_LOCKED");
                        break;
                    case CaptureResult.CONTROL_AF_STATE_PASSIVE_UNFOCUSED:
                        mUiHandler.removeCallbacks(mLockAutoFocusRunnable);
                        //mUiHandler.postDelayed(mLockAutoFocusRunnable, LOCK_FOCUS_DELAY_ON_UNFOCUSED);
                        Log.d(TAG, "CaptureResult.CONTROL_AF_STATE_PASSIVE_UNFOCUSED");
                        break;
                    case CaptureResult.CONTROL_AF_STATE_PASSIVE_SCAN:
                        Log.d(TAG, "CaptureResult.CONTROL_AF_STATE_PASSIVE_SCAN");
                        break;
                    case CaptureResult.CONTROL_AF_STATE_PASSIVE_FOCUSED:
                        mUiHandler.removeCallbacks(mLockAutoFocusRunnable);
                        //mUiHandler.postDelayed(mLockAutoFocusRunnable, LOCK_FOCUS_DELAY_ON_FOCUSED);
                        Log.d(TAG, "CaptureResult.CONTROL_AF_STATE_PASSIVE_FOCUSED");
                        break;
                }
            }
            mLastAfState = afState;
            break;
        }

And replace all occurrences of:

mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AF_MODE,
                                            CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);

With:

if (isAutoFocusSupported())
                                mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AF_MODE,
                                        CaptureRequest.CONTROL_AF_MODE_AUTO);
                            else
                                mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AF_MODE,
                                        CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);