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);
             }
         }