OpenCV camera calibration error: OpenCV Error: Unknown error code -49 (Input file is empty) in cvOpenFileStorage

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I'm trying to calibrate my PICamera with the camera_calibration.cpp sample. I have taken 6 images from the sample chessboard. cmake and make work, but after running camera_calibration got the following error:

./camera_calibration default.xml
This is a camera calibration sample.
Usage: calibration configurationFile
Near the sample file you'll find the configuration file, which has detailed help of how to edit it.  It may be any OpenCV supported file format XML/YAML.
OpenCV Error: Unknown error code -49 (Input file is empty) in cvOpenFileStorage, file /tmp/binarydeb/ros-kinetic-opencv3-3.2.0/modules/core/src/persistence.cpp, line 4422
terminate called after throwing an instance of 'cv::Exception'
  what():  /tmp/binarydeb/ros-kinetic-opencv3-3.2.0/modules/core/src/persistence.cpp:4422: error: (-49) Input file is empty in function cvOpenFileStorage

Aborted (core dumped)

Google doesn't want to give me an answer this time, hope someone else does. I used this http://docs.opencv.org/2.4/doc/tutorials/calib3d/camera_calibration/camera_calibration.html guide.

I have all the files, images,... in 1 folder. default.xml

<?xml version="1.0"?>
<opencv_storage>
<Settings>
  <!-- Number of inner corners per a item row and column. (square, circle) -->
  <BoardSize_Width> 9</BoardSize_Width>
  <BoardSize_Height>6</BoardSize_Height>

  <!-- The size of a square in some user defined metric system (pixel, millimeter)-->
  <Square_Size>27</Square_Size>

  <!-- The type of input used for camera calibration. One of: CHESSBOARD CIRCLES_GRID ASYMMETRIC_CIRCLES_GRID -->
  <Calibrate_Pattern>"CHESSBOARD"</Calibrate_Pattern>

  <!-- The input to use for calibration.
        To use an input camera -> give the ID of the camera, like "1"
        To use an input video  -> give the path of the input video, like "/tmp/x.avi"
        To use an image list   -> give the path to the XML or YAML file containing the list of the images, like "/tmp/circles_list.xml"
        -->
  <Input>"VID5.xml"</Input>
  <!--  If true (non-zero) we flip the input images around the horizontal axis.-->
  <Input_FlipAroundHorizontalAxis>0</Input_FlipAroundHorizontalAxis>

  <!-- Time delay between frames in case of camera. -->
  <Input_Delay>100</Input_Delay>

  <!-- How many frames to use, for calibration. -->
  <Calibrate_NrOfFrameToUse>26</Calibrate_NrOfFrameToUse>
  <!-- Consider only fy as a free parameter, the ratio fx/fy stays the same as in the input cameraMatrix.
       Use or not setting. 0 - False Non-Zero - True-->
  <Calibrate_FixAspectRatio> 1 </Calibrate_FixAspectRatio>
  <!-- If true (non-zero) tangential distortion coefficients  are set to zeros and stay zero.-->
  <Calibrate_AssumeZeroTangentialDistortion>1</Calibrate_AssumeZeroTangentialDistortion>
  <!-- If true (non-zero) the principal point is not changed during the global optimization.-->
  <Calibrate_FixPrincipalPointAtTheCenter> 1 </Calibrate_FixPrincipalPointAtTheCenter>

  <!-- The name of the output log file. -->
  <Write_outputFileName>"out_camera_data.xml"</Write_outputFileName>
  <!-- If true (non-zero) we write to the output file the feature points.-->
  <Write_DetectedFeaturePoints>1</Write_DetectedFeaturePoints>
  <!-- If true (non-zero) we write to the output file the extrinsic camera parameters.-->
  <Write_extrinsicParameters>1</Write_extrinsicParameters>
  <!-- If true (non-zero) we show after calibration the undistorted images.-->
  <Show_UndistortedImage>1</Show_UndistortedImage>

</Settings>
</opencv_storage>

VID5.xml

<opencv_storage>
<style type="text/css" id="night-mode-pro-style"/>
<link type="text/css" rel="stylesheet" id="night-mode-pro-link"/>
<images>
57.jpg ...