how to increase fps camera?

edit

hi, I wrote a program with opencv's camera(CvCameraViewListener2) but my program is running so slowly(max 20 fps) on LG G3. However,my program has not any processing. How can i increase fps or fix it on 24 or 25 fps?

    public class activity extends Activity implements CvCameraViewListener2 {
    private static final String    TAG                 = "OCVSample::Activity";
    private CameraBridgeViewBase   mOpenCvCameraView;
    private Mat                    mRgba;
    private Mat                    mGray;

    private BaseLoaderCallback  mLoaderCallback = new BaseLoaderCallback(this) {
        @Override
        public void onManagerConnected(int status) {
            switch (status) {
                case LoaderCallbackInterface.SUCCESS:
                {
                    Log.i(TAG, "OpenCV loaded successfully");


                    mOpenCvCameraView.enableView();

                } break;
                default:
                {
                    super.onManagerConnected(status);
                } break;
            }
        }
    };


    public activity() {

        Log.i(TAG, "Instantiated new " + this.getClass());
    }

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        Log.i(TAG, "called onCreate");

        super.onCreate(savedInstanceState);
        getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);

        setContentView(R.layout.face_detect_surface_view);
        mOpenCvCameraView = (CameraBridgeViewBase) findViewById(R.id.fd_activity_surface_view);

        mOpenCvCameraView.setCvCameraViewListener(this); 

        mOpenCvCameraView.setMaxFrameSize(320, 240);
        mOpenCvCameraView.enableFpsMeter();
        Log.i(TAG, "setMaxFrameSize");
    }

    @Override
    public void onPause()
    {
        Log.i(TAG, "called onPause");
        super.onPause();
        if (mOpenCvCameraView != null)
            mOpenCvCameraView.disableView();
    }

    @Override
    public void onResume()
    {
        Log.i(TAG, "called onResume");
        super.onResume();
        OpenCVLoader.initAsync(OpenCVLoader.OPENCV_VERSION_2_4_9, this, mLoaderCallback);
    }

    public void onDestroy() {
        Log.i(TAG, "called onDestroy");
        super.onDestroy();
        if (mOpenCvCameraView != null)
            mOpenCvCameraView.disableView();
    }

    public void onCameraViewStarted(int width, int height) {
        Log.i(TAG, "called onCameraViewStarted");
        mGray = new Mat();
        mRgba = new Mat();
    }

    public void onCameraViewStopped() {
        Log.i(TAG, "called onCameraViewStopped");
        mGray.release();
        mRgba.release();
    }

    public Mat onCameraFrame(CvCameraViewFrame inputFrame) {
        Log.i(TAG, "called onCameraFrame");

        mRgba = inputFrame.rgba();
        mGray = inputFrame.gray();
        return mGray;
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        Log.i(TAG, "called onCreateOptionsMenu");


        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        Log.i(TAG, "called onOptionsItemSelected; selected item: " + item);

        return true;
    }

}