I am trying to use a combo of oxfOpenCv and OpenCv calls. I am also using the gstreamer videograbber so kindly provided by arturo here. I am on Ubuntu 9.04 and Code::Blocks.
I have managed to narrow down my problem and reproduce it in the following way.
If I take the movieGrabber example as provided in the link above it works perfectly with my webcam. If however I add -lhighgui to Build Options … Linker Settings … Other linker options, it stops working.
The message is
‘GstAppSink’ has no property name ‘emit-signals’ and gives a segmentation fault.
If I run this in the debugger it stops in file ofGstUtils in this function.
void ofGstDataLock(ofGstVideoData * data){
pthread_mutex_lock( &(data->buffer_mutex) );
}
on the pthread_mutex_lock call(line 29). There is more info in the call stack. This makes me think something in highgui is messing with the mutex, even though I am not even making any calls to anything in highgui, I don’t even have any headers included, nothing from highgui should be running as I see it. The example is complete unchanged except for the -lhighgui at link time.
I’ve been able to combine a libdc1394 grabber with highgui on linux successfully before but I haven’t tried the Gstreamer one.
However, in your case perhaps there’s some namespace corruption. Try moving changing the order of the linking…i.e. put -lhighgui right at the end of the linking so that it doesn’t get picked up first.
In my mission to set the link order, I decided to fill the library in the link libraries of the project as highgui rather than as an extra setting in the form of -lhighgui. And now the problem has gone! So it must have been something with the order, I couldn’t see the order in the build messages or build log nor could I find it in the Makefile but since it is working I am not going to mess with it.
I have exactly the same problem with pthread_mutex_lock and changing libraries order in gcc link command does not seems to have any effect. I haded -pthread to the compilers flags and -lpthread to the linker flags.
i try to run opencvExample on ubuntu 10.04 with openframworks on codebloks, i have “segmentation fault”, someone talk about changing the linker, how can i do it. i don’t see build options on main menu.
thanks folks!
