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);
}
}