JMF with Native Libraries as Signed Applet

Question

Hello
After spending a few days hunting through forums, digging into JMF source code and hacking in the dark I'm about to give up, but thought I'd start yet another thread on this. It's a long, sad story...
Problem: Deploying a JMF based program that relies on native libraries (in this case the FOBS4JMF bindings) as an applet: how to get jmf.properties and the native libraries loaded properly.
Partial Solution: the native libraries packaged in a signed jar file, added to the applet's archive property, extracted using getResourceAsStream(), and loaded using System.load(). This is how FOBS4JMF loads it's native library anyway (via the com.moesol.NativeLibraryFinder):
Class classInApplet; // name of a class loaded by the applet
File outputFile; // location for extracted library
InputStream is = classInApplet.getResourceAsStream(resource);
copyStream(is, outputFile);
System.load(outputFile.getAbsolutePath());Why this doesn't really work:
(a) JMF (com.media.util.Registry) only searches for jmf.properties (which contains the instructions to use the FOBS4JMF plugin) in real folders (i.e. not jars) on the classpath of the local machine. I could extract the jmf.properties to a folder on the local machine, but have no way of making sure that folder would be on the classpath. Calls to "System.getProperty("java.class.path") give varying results - including an empty string on FF/OSX. Even if i could get the classpath somehow, chances are that it wouldn't contain any folders writable under Vista's UAC, which would leave me out of luck.
JMF also looks for a file called ".jmfdir" in various platform specific locations, and appends the contents of this file to the classpath, so if i could write to that file i'd be golden. This seems like it would work on non windows platforms, because JMF looks for that in "user.home"). However, from what i can tell, on windows, JMF uses a native call to a function called nGetUserHome() to determine where to find .jmfdir - which leads to the second problem...
(b) the JMF native libraries are loaded through calls to System.loadLibrary(), not System.load(), which means that they have to be on the "java.library.path" in order to be found - and again, I have no way of extracting the libraries to a directory on that path (at least not one writable under Vista UAC). This wouldn't be a problem, as I could pre-load the libraries myself with System.load(), except that JMF throws an exception if it can't find one, and stops trying to do whatever it thinks it needs the library for. Again, not a problem if I use only the FOBS4JMF native code (though i would like to use the DirectAudio renderer on windows) - except that the nGetUserHome() function described above is in a native library (jmutil.dll). So, when com.media.util.Registry.getJMFDir() tries to find ".jmfdir" it first tries to load "jmutil.dll" using System.loadLibrary(). This throws an exception inf "jmutil.dll" is not on the "java.library.path", and com.media.util.Registry.getJMFDir() returns null. Here's the relevant code from com.media.util.Registry.getJMFDir() - with my annotations
All of these problems are fixable by relatively minor tweaks to the JMF source - but I don't think that's allowed under the SCSL. So if anyone has any, i mean ANY other suggestions, please BRING 'EM ON.
thanks
-chris
EDIT: just for kicks, i checked to see where JMF expects to find .jmfdir on windows - ie the result of nGetUserHome(). At least on XP this seems to be c:\WINDOWS. if it's the same on Vista, then fixing the loadLibrary problem won't help bc I still won't be able to write to this file.
Edited by: wodenx on May 7, 2010 9:46 AM

Answer 1

Hi-
Thanks for responding so quickly.
As far as the natives go, you might try using the new JNLP embedded applet ability in the plugin2 architecture.I was going to look into that, but decided it wasn't necessary since I can get the FOBS native code to link properly. It's really the registry that's the problem, since without solving that I can't get JMF to USE the FOBS code.
Can you get it all to work if the JMF installer is invoked? If so, perhaps if you add an installer-desc that calls the normal JMF setup.exe (though that final warning to reboot is both unnecessary and odious).I don't think it would work even with the JMF installer, bc I need to point JMF at the FOBS specific jmf.properties. I might be get it to work by invoking my own installer though, to place my jmf.properties somewhere in the native class path, so that's worth looking at. Thank you. Problem there is that on Vista users would have to elevate to run the applet, which is not ideal.necessary and odious).
Why do you particularly want to embed media in a web page?The customer may want it. I might be able to convince them to go with JNLP/WebStart, but I think I might have the same problem there. Please correct me if I'm wrong...
I've also read that there are problems with JMF and JNLP owing to the fact that JMF doesn't recognize the security manager invoked by JNLP, and so gives your program no permissions. Haven't tried it myself yet.
Thanks again!
Edited by: wodenx on May 7, 2010 12:07 PM