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。

 1 // See android.hardware.Camera.Parameters.setRotation for  
 2         // documentation.  
 3         // Note that mOrientation here is the device orientation, which is the opposite of  
 4         // what activity.getWindowManager().getDefaultDisplay().getRotation() would return,  
 5         // which is the orientation the graphics need to rotate in order to render correctly.  
 6         int rotation = 0;  
 7         if (mOrientation != OrientationEventListener.ORIENTATION_UNKNOWN) {  
 8             CameraInfo info = CameraHolder.instance().getCameraInfo()[mCameraId];  
 9             if (info.facing == CameraInfo.CAMERA_FACING_FRONT) {  
10                 rotation = (info.orientation - mOrientation + 360) % 360;  
11             } else {  // back-facing camera  
12                 rotation = (info.orientation + mOrientation) % 360;  
13             }  
14         } else {  
15             //Get the right original orientation  
16             CameraInfo info = CameraHolder.instance().getCameraInfo()[mCameraId];  
17             rotation = info.orientation;  
18         }  
19 //        mMediaRecorder.setOrientationHint(rotation);  
20   
21         if (mCameraId == CameraInfo.CAMERA_FACING_FRONT) {  
22             if (rotation == 270 || rotation == 90 || rotation == 180) {  
23                 mMediaRecorder.setOrientationHint(180);  
24             } else {  
25                 mMediaRecorder.setOrientationHint(0);  
26             }  
27         } else {  
28             if (rotation == 180){  
29                 mMediaRecorder.setOrientationHint(180);  
30             }else{  
31                 mMediaRecorder.setOrientationHint(0);  
32             }  
33         }