# StereoRectifyUncalibrated "cannot solve under-determined linear system"

Hi all

I'm using cv2.stereoRectifyUncalibrated to try and calculate the appropriate rectification transformation between two sets of artificial correspondences:

```
import cv2
import cv2.cv as cv
import numpy as np
pts1 = [[423, 191], # top_l
[840, 217], # top_r
[422, 352], # bot_l
[838, 377], # bot_r
[325, 437], # front_l
[744, 464], # front_r
[288, 344], # wide_l
[974, 388]] # wide_r
pts2 = [[423, 192], # top_l
[841, 166], # top_r
[422, 358], # bottom_l
[839, 330], # bottom_r
[518, 440], # front_l
[934, 417], # front_r
[287, 363], # wide_l
[973, 320]] # wide_r
pts1 = np.array(pts1, dtype='f4')
pts2 = np.array(pts2, dtype='f4')
f, mask = cv2.findFundamentalMat(pts1, pts2, cv2.cv.CV_FM_8POINT)
pts1_r = pts1.reshape((pts1.shape[0] * 2, 1))
pts2_r = pts2.reshape((pts2.shape[0] * 2, 1))
ret, H1, H2 = cv2.stereoRectifyUncalibrated(pts1_r, pts2_r, f, (1280, 720))
print ret
```

I've included the data initialisation just to illustrate the array structure. You'll see I've avoided the assertion error mentioned in this discussion using reshape.

However, I now get the following error:

OpenCV Error: Bad argument (The function can not solve under-determined linear systems) in solve, file /tmp/opencv20150527-4924-hjrvz/opencv-2.4.11/modules/core/src/lapack.cpp, line 1350

Out of context, the offending snippet looks like this:

```
int m = src.rows, m_ = m, n = src.cols, nb = _src2.cols;
...
if( m < n )
CV_Error(CV_StsBadArg, "The function can not solve under-determined linear systems" );
```

Where m and n are the number of rows and columns in 'inputArray' - supplied to cv::solve by cvsolve, and created somewhere in StereoRectifyUncalibrated.

My question is simply: what is going on here? I'm struggling to see how my artificial data could be responsible for the system being solved to be under-determined.