First, you need to make sure you have the cross-compiler working. Try to create very simple “Hello world” application and compile it for your ARM7. This simple app should use only standard c library. When you successfully compiled, linked and executed your simple app on your target ARM hardware, use the guide in post to cross-compile the opencv library.

Best Regards,
Yuri Vashchenko

Segmentation fault may be caused by many different issues.

You provided too little information on you problem, so I cannot give you any specific solution. As this thread is related to compiling the OpenCV library, I’d like you to make sure you have correctly compiled OpenCV library itself.

Start with running OpenCV’s “configure” script, then “make”, then “install” the Library. If you get any errors during this process, you need to solve them first.
Then, write a very basic (just a few lines) application that uses OpenCV library. You may use any of the OpenCV’s examples found in distribution package. Compile it and execute. If you made everything right, it should run without any issues. When you verified that OpenCV itself is built and installed correctly, you may start to debug more complex applications.

Hope this helps,

Best Regards,
Yuri Vashchenko

‘g++ –version’ produced the following output:

g++ (Ubuntu/Linaro 4.4.4-14ubuntu5) 4.4.5
Copyright (C) 2010 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Appreciate any help in this regard as this is very critical for my thesis. If it doesn’t work, I’ll have to return to Windows which I don’t really like.

Thanks,
Ramaraju

As far as I understand, the problem is with your OpenCv library. It looks like you are trying to compile a sample for ARM using libraries compiled for x86. Your directive “-L/usr/local/lib” tells the linker to look for libraries at “-L/usr/local/lib”, where probably Ubuntu (x86) libraries are stored. You need to recompile the whole OpenCV for your target platform.

Hope this helps,
Best Regards,
Yuri Vashchenko

I’m a beginner in embedded and I would like to ask you for support.
I’m trying to cross compile a test file using Sourcery_G++_Lite_for_ARM_GNU_Linux and the cross compilation fails in the following way:

ric@ubuntu:~/CodeSourcery/gnueabi/samples$ arm-none-linux-gnueabi-gcc -I/usr/local/include/opencv -L/usr/local/lib -lcv -lhighgui -lcxcore -lcvaux contours.c -o contours
cc1: warning: include location “/usr/local/include/opencv” is unsafe for cross-compilation
/home/ric/CodeSourcery/gnueabi/bin/../lib/gcc/arm-none-linux-gnueabi/4.4.1/../../../../arm-none-linux-gnueabi/bin/ld: warning: library search path “/usr/local/lib” is unsafe for cross-compilation
/home/ric/CodeSourcery/gnueabi/bin/../lib/gcc/arm-none-linux-gnueabi/4.4.1/../../../../arm-none-linux-gnueabi/bin/ld: skipping incompatible /usr/local/lib/libcv.so when searching for -lcv
/home/ric/CodeSourcery/gnueabi/bin/../lib/gcc/arm-none-linux-gnueabi/4.4.1/../../../../arm-none-linux-gnueabi/bin/ld: cannot find -lcv
collect2: ld returned 1 exit status

The host is an ubuntu_10.04.1 VM on a Windows XP Laptop, target will be an ARM based IGEPV2 board.
CV libs seems to be correctly installed since I can compile using gcc in the host and execute and execute on it.
About Cross compilation tool, after installing there were created two folders :
/usr/local/lib :

lrwxrwxrwx 1 root root 15 2011-01-03 02:37 libcvaux.so -> libcvaux.so.2.0
lrwxrwxrwx 1 root root 17 2011-01-03 02:37 libcvaux.so.2.0 -> libcvaux.so.2.0.0
-rw-r–r– 1 root root 1162062 2011-01-03 02:34 libcvaux.so.2.0.0
lrwxrwxrwx 1 root root 12 2011-01-03 02:37 libcv.so -> libcv.so.2.0
lrwxrwxrwx 1 root root 14 2011-01-03 02:37 libcv.so.2.0 -> libcv.so.2.0.0
-rw-r–r– 1 root root 2057645 2011-01-03 02:33 libcv.so.2.0.0
lrwxrwxrwx 1 root root 16 2011-01-03 02:37 libcxcore.so -> libcxcore.so.2.0
lrwxrwxrwx 1 root root 18 2011-01-03 02:37 libcxcore.so.2.0 -> libcxcore.so.2.0.0
-rw-r–r– 1 root root 2711305 2011-01-03 02:31 libcxcore.so.2.0.0
lrwxrwxrwx 1 root root 17 2011-01-03 02:37 libhighgui.so -> libhighgui.so.2.0
lrwxrwxrwx 1 root root 19 2011-01-03 02:37 libhighgui.so.2.0 -> libhighgui.so.2.0.0
-rw-r–r– 1 root root 247528 2011-01-03 02:33 libhighgui.so.2.0.0
lrwxrwxrwx 1 root root 12 2011-01-03 02:37 libml.so -> libml.so.2.0
lrwxrwxrwx 1 root root 14 2011-01-03 02:37 libml.so.2.0 -> libml.so.2.0.0
-rw-r–r– 1 root root 446543 2011-01-03 02:33 libml.so.2.0.0
drwxr-xr-x 2 root root 4096 2011-01-03 02:37 pkgconfig
drwxrwsr-x 4 root staff 4096 2010-08-16 02:35 python2.6

and /usr/local/include/opencv :

-rw-r–r– 1 root root 63883 2010-12-31 08:28 cvaux.h
-rw-r–r– 1 root root 51258 2010-12-31 08:28 cvaux.hpp
-rw-r–r– 1 root root 40678 2010-12-31 08:28 cvcompat.h
-rw-r–r– 1 root root 71716 2010-12-31 08:28 cv.h
-rw-r–r– 1 root root 43897 2010-12-31 08:28 cv.hpp
-rw-r–r– 1 root root 12503 2010-12-31 08:28 cvtypes.h
-rw-r–r– 1 root root 2538 2010-12-31 08:28 cvver.h
-rw-r–r– 1 root root 41990 2010-12-31 08:28 cvvidsurv.hpp
-rw-r–r– 1 root root 20730 2010-12-31 08:28 cvwimage.h
-rw-r–r– 1 root root 87498 2010-12-31 08:28 cxcore.h
-rw-r–r– 1 root root 81321 2010-12-31 08:28 cxcore.hpp
-rw-r–r– 1 root root 8757 2010-12-31 08:28 cxerror.h
-rw-r–r– 1 root root 6937 2010-12-31 08:28 cxflann.h
-rw-r–r– 1 root root 152510 2010-12-31 08:28 cxmat.hpp
-rw-r–r– 1 root root 27967 2010-12-31 08:28 cxmisc.h
-rw-r–r– 1 root root 86570 2010-12-31 08:28 cxoperations.hpp
-rw-r–r– 1 root root 53713 2010-12-31 08:28 cxtypes.h
-rw-r–r– 1 root root 18165 2010-12-31 08:28 highgui.h
-rw-r–r– 1 root root 4652 2010-12-31 08:28 highgui.hpp
-rw-r–r– 1 root root 72650 2010-12-31 08:28 ml.h

Does anybody knows the cause of that problem?

Thanks in advance!

Thanks

ld: cannot find -lcv means that your linker cannot find library libcv.a. Do you have this file built? What you probably need to do is to check if this library was actually created and if your path where linker looks for this lib contains a correct directory. See section “Compile and link, 1.3″ above.

Hope this helps,

Best regards,
Yuri Vashchenko

I am trying to cross-compile a armtest.c file using arm-linux-gcc ,
toolchain 4.3.2. The .c file is using open cv2.0.0 libraries. when I try to
cross compile the file, the following error is coming

root@tanushri-desktop:~# arm-linux-gcc -o2 -I/usr/local/include/
opencv armtest.c -L//root/Downloads/OpenCV-2.0.0/src/.libs -lcv -
lhighgui -lcxcore -lml -lcvaux -lrt -lpthread -ldl -lz -lpng12 -ljpeg -
o armtest
cc1: warning: include location “/usr/local/include/opencv” is unsafe
for cross-compilation
In file included from /usr/local/include/opencv/cxcore.h:70,
from /usr/local/include/opencv/cv.h:58,
from armtest.c:12:
/usr/local/include/opencv/cxtypes.h: In function ‘cvRound’:
/usr/local/include/opencv/cxtypes.h:240: warning: incompatible
implicit declaration of built-in function ‘lrint’
/opt/usr/local/arm/4.3.2/bin/../lib/gcc/arm-none-linux-gnueabi/
4.3.2/../../../../arm-none-linux-gnueabi/bin/ld: cannot find -lcv

HELP!

We did not use any tools to change doubles to fixed point operation.
We rewrote the big part of opencv manually.

Unfortunately, it had not given significant improvement in performance on our target ARM platform.

So, if you need fixed point operations for your DSP of whatever your target platform is, you will probably have to rewrite a part of opencv code yourself.

Start with running a profiler on your target platform to understand which code takes most of the execution time.
Then, using opencv source code, try to understand how it works and start replacing double precision variables and operations with fixed point ones. In our experiments, we even had been able to rewrite some code to use 32 bit integers only. It affected precision in some cases, but until overall quality is acceptable, you can do such trade-offs.

Hope this helps,

Best regards,
Yuri