android Camera 录像时旋转角度

录像保存时，旋转角度要与所拍录像时的角度保持一致，否则，看起来就会出现角度不度，巅倒等问题。

一般在开始录像之前会先去初始化录像

initializeRecorder 中会去读取当前的录像或拍照的旋转角度，并跟据当前的角度来选择一个角度写到所拍

照片或者视频的 exif 信息中去。

// See android.hardware.Camera.Parameters.setRotation for  
        // documentation.  
        // Note that mOrientation here is the device orientation, which is the opposite of  
        // what activity.getWindowManager().getDefaultDisplay().getRotation() would return,  
        // which is the orientation the graphics need to rotate in order to render correctly.  
        int rotation = 0;  
        if (mOrientation != OrientationEventListener.ORIENTATION_UNKNOWN) {  
            CameraInfo info = CameraHolder.instance().getCameraInfo()[mCameraId];  
            if (info.facing == CameraInfo.CAMERA_FACING_FRONT) {  
                rotation = (info.orientation - mOrientation + 360) % 360;  
            } else {  // back-facing camera  
                rotation = (info.orientation + mOrientation) % 360;  
            }  
        } else {  
            //Get the right original orientation  
            CameraInfo info = CameraHolder.instance().getCameraInfo()[mCameraId];  
            rotation = info.orientation;  
        }  
//        mMediaRecorder.setOrientationHint(rotation);  
  
        if (mCameraId == CameraInfo.CAMERA_FACING_FRONT) {  
            if (rotation == 270 || rotation == 90 || rotation == 180) {  
                mMediaRecorder.setOrientationHint(180);  
            } else {  
                mMediaRecorder.setOrientationHint(0);  
            }  
        } else {  
            if (rotation == 180){  
                mMediaRecorder.setOrientationHint(180);  
            }else{  
                mMediaRecorder.setOrientationHint(0);  
            }  
        }