error in findStereoCorrespondenceBM

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Hi all,

I'm trying to implement 3D reconstruction, but I can't go over this error:

I'm reading images from stereo cameras as IplImage. I convert the IplImage in Mat and then in cvMat.

CvMat l_rect = cvMat(imageSize_l.height, imageSize_l.width, CV_8UC1);

The error appears in the findStereoCorrespondenceBM function:

OpenCV Error: Unsupported format or combination of formats (Both input images must have CV_8UC1) in findStereoCorrespondenceBM

How can I solve this problem?

Thank you