My GStreamer-based application crashes on startup with errors about unfound schedulers on the command-line. I get undefined behaviour as soon as any GStreamer element is being initialized. Your registry is probably missing, or it is outdated (i.e. not updated after a recent upgrade). Fix this by running gst-register yourself: gst-register In the worst case, you might have to run it both as user and as root. Note that package managers are suggested to run this automatically during the post-installation. Our RPMs and Debian packages do just that. Some application is telling me that I am missing a plug-in. What do I do ? Well, start by checking if you really are missing the plug-in. gst-inspect (plug-in) and replace (plug-in) with the plug-in you think is missing. If this doesn't return any result, then you either don't have it or your registry cannot find it. If you're not sure either way, then chances are good that you don't have it. You should get the plug-in and run gst-register to register it. How to get the plug-in depends on your distribution. if you run GStreamer using packages for your distribution, you should check what packages are available for your distribution and see if any of the available packages contains the plug-in. if you run GStreamer from a source install, there's a good chance the plug-in didn't get built because you are missing an external library. When you ran configure, you should have gotten output of what plug-ins are going to be built. You can re-run configure to see if it's there. If it isn't, there is a good reason why it is not getting built. The most likely is that you're missing the library you need for it. Check the README file in gst-plugins to see what library you need. Make sure to remember to re-run configure after installing the supporting library ! if you run GStreamer from CVS, the same logic applies as for a source install. Go over the reasons why the plug-in didn't get configured for build. Check output of config.log for a clue as to why it doesn't get built if you're sure you have the library needed installed in a sane place. I get an error that says something like (process:26626): GLib-GObject-WARNING **: specified instance size for type `DVDReadSrc' is smaller than the parent type's `GstElement' instance size What's wrong ? If you run GStreamer CVS uninstalled, it means that something changed in the core that requires a recompilation in the plugins. Recompile the plugins by doing "make clean && make". If you run GStreamer installed, it probably means that you run the plugins against a different (incompatible) version than they were compiled against, which ususally means that you run multiple installations of GStreamer. Remove the old ones and - if needed - recompile again to ensure that it is using the right version. Note that we strongly recommend using Debian or RPM packages, since you will not get such issues if you use provided packages. The GStreamer application I used stops with a segmentation fault. What can I do ? There are two things you can do. If you compiled GStreamer with specific optimization compilation flags, you should try recompiling GStreamer, the application and the plug-ins without any optimization flags. This allows you to verify if the problem is due to optimization or due to bad code. Second, it will also allow you to provide a reasonable backtrace in case the segmentation fault still occurs. The second thing you can do is look at the backtrace to get an idea of where things are going wrong, or give us an idea of what is going wrong. To provide a backtrace, you should run the application in gdb by starting it with gdb (gst-application) (If the application is in a source tree instead of installed on the system, you might want to put "libtool" before "gdb") Pass on the command line arguments to the application by typing set args (the arguments to the application) at the (gdb) prompt Type "run" at the (gdb) prompt and wait for the application to segfault. The application will run a lot slower, however. After the segfault, type "bt" to get a backtrace. This is a stack of function calls detailing the path from main () to where the code is currently at. If the application you're trying to debug contains threads, it is also useful to do info threads and get backtraces of all of the threads involved, by switching to a different thread using "thread (number)" and then again requesting a backtrace using "bt". If you can't or don't want to work out the problem yourself, a copy and paste of all this information should be included in your bug report.