Java Sound for Linux Netscape

As far as I can tell, the Linux version of Netscape Navigator/Communicator (the latest release as of this writing was Netscape Communicator 4.6) does not support the playing of sound by Java applets.

I have hacked up a replacement for Netscape's implementation of (the Java class) sun.audio.AudioDevice (including some JRI native C code) which enables the Netscape Java VM to play sound.

News

• The server the signing certificates was on died, so the links to the certificates have been updated.
• My cheapskate self-generated signing certificate has expired again. You'll probably want to download the new one. (See below.)
• Libmmoss now supports EsounD. (See below.)

The Hacks

Here's a gzipped tar file with the source and binaries for my hacks:

• libmmoss-2.1a.tar.gz (approx. 60 kb)
  (Changes from previous versions are listed below.)

To use these hacks you (most probably) need:

1. Linux. Right now I'm running 2.2.9, I used to run with 2.0.xx and it worked then. As far as I know 2.1.xx should work fine too.
2. A supported sound driver. I'm using the stock OSS/Free driver which is bundled with the 2.2.9 kernel. Any modestly recent version of this driver (or the commercial version) should work. For awhile I used the new ALSA sound driver (version 0.2.0pre8) which seemed to work fine too. As of 2.0, libmmoss supports EsounD as well. It is important that you either have a working /dev/audio device file, or a working esd.
3. A soundcard. I'm using a cheapie ES1688 clone. Anything that works with your sound driver should be fine.
4. Netscape Communicator 4.xx. Older versions of this code worked with Navigator 3.01. I think this version should as well, but I haven't tested it with 3.01. (You can get netscape here.)

Installation

Precompiled binaries are included with this distribution, so no compilation should be necessary.

The kludge consists of three parts:

The compiled, hacked-up Java code.

This is contained in the libmmoss.jar JAR file. (Navigator 3.01 doesn't know about JAR files, if you are using 3.01, you will have to install the individual class files by hand. See below.)

The compiled native code.

This is in the shared library libmmoss.so.

A wrapper shell-script.

This sets up environment variables so that netscape can find the hacks, then runs the real netscape.

``Automatic'' Installation

If you're running Netscape Communicator 4.xx, the included Makefile should be able to install the hacks for you. (If it doesn't work, or if you'd like to install the hacks manually, see the next section. (If you are running Navigator 3.xx, see the old installation notes below.)

1. Inspect and edit the Makefile. Pay particular attention to the settings of MOZILLA_HOME which specifies where you have installed Communicator. Also check the settings of pkgdir and bindir, which control where the hacks will be installed.
2. Run `make'. This should generate the netscape wrapper, netscape.sh.
3. Inspect and edit netscape.sh. It may need modification, particularly if you have other fancy plugins (e.g. Acrobat Reader, RealAudio player, etc...) installed. There are notes at the end of netscape.sh regarding how I've dealt with these.
4. Important Note: Before you do the next step, know that 'make install' will install the wrapper script (by default) in /usr/local/bin/netscape. It will overwrite any wrapper script (or binary) you might already have installed there so make sure this is okay!
5. Run `make install' to install the hacks. You probably need to become root to do this, unless you've modified the paths in the Makefile to point to directories in which you have write permission.
6. Make sure your PATH includes bindir, the directory in which the wrapper was installed (default: /usr/local/bin).
7. You may want to load this CA certificate. (More on this below.)
8. Try it out. Run `netscape'. Then see the section on testing below.

Manual Installation

• The files libmmoss.so and libmmoss.jar need to be installed somewhere.
• Then you'll need to make a wrapper for netscape which will set environment variables so that netscape can find these files at the right time. Basically, libmmoss.jar should be mentioned in CLASSPATH, and libmmoss.so should be in a directory which is mentioned by LD_LIBRARY_PATH.
• It is important that libmmoss.jar is listed in CLASSPATH before netscape's JAR's, in particular java40.jar. This is because libmmoss.jar contains classes which shadow the classes in java40.jar.
• You may want to load this CA certificate. (More on this below.)

Annoying Popup Windows?

With Communicator 4.xx (and later), when my code loads, you will get a dialog box which requests permission to load a native library. You'll have to grant permission for the hacks to work. As of libmmoss version 2.0, you'll also be asked to grant permission to make network connections. You only really need to grant this if you want the EsounD support.

Since, I'm not about to pay money to obtain a certified signing certificate, if you want to be able to verify the signature on the libmmoss.jar file, you'll have to download (and trust) this certificate. You only need to do this if you want the ``Remember This Decision'' checkbox on the popup dialog to work. (Note that my old certificate and the one before that even have expired, so even if you've downloaded the certificate(s) for previous versions of libmoss, you'll still have to download the new one.) (FWIW, the fingerprint of the certificate is 6D:7D:D6:AD:9C:E0:30:EE:CC:26:DD:24:AA:0A:9C:6A.)

EsounD

Libmmoss can now output sound through esd, the EsounD sound daemon. You do not need to do anything special to enable esd support, libmmoss will, if possible, output to esd and fall back to /dev/audio output, if not.

The ESPEAKER environment variable, if set, is used to find the esd. Esd support can be disabled by setting ESPEAKER to none.

Currently the esd support works okay but not great for me. Problems include:

• Audio output hiccups and burps, particularly if esd is running at an output rate other than it's default of 44.1 khz.
• Lousy fidelity. Mostly due to the less than ideal algorithm esd's uses to resample from the 8 khz stream I send it to the 44.1 khz it plays. Hopefully this will get fixed on the esd side some day.
• I suspect things will not go so well if you are trying to play audio to a remote esd over a anything but a pretty-fast LAN connection.

I'd appreciate feedback on how well the esd support is working for you. Drop me a note with any comments or suggestions.

Testing

Javasoft has a dog-barking, train-whistling demo in their tutorial. (You have to find the applet, and then hit some buttons.)

They also have a more vocal demo here.

Troubleshooting

If you have trouble getting libmmoss to work, the first thing you should do is take a look at Netscape's Java Console while trying to play sounds. (In Communicator 4.x, you can get to the Java Console via the menubar: select Communicator->Tools->Java Console.)

The first time you try to play a sound, libmmoss will print an identifying message on the Java Console. If you do not see something like

Loading Libmmoss-2.0
    Java sound for Linux Netscape
    by G. T. Dairiki 
    (see  http://www.alumni.caltech.edu/~dairiki/libmmoss/ )

Once you get past the ``Loading Libmmoss'' message, libmmoss should spew various messages which may or may not help determine why you're not getting any sound.

If you get really stuck, feel free to e-mail me. If possible, include whatever Java Console output you get in your note.

Appendix A - Installation for Navigator 3.01

Since Navigator does not know about JAR files, you must install the individual class files, of which there are now four:

• sun/audio/AudioDevice.class
• sun/audio/AudioDevice$AudioException.class
• sun/audio/AudioDevice$AudioBusyException.class
• sun/audio/AudioDevice$NoAudioDeviceException.class

The environment variables LD_LIBRARY_PATH, and CLASSPATH should probably be set something like:

export LD_LIBRARY_PATH=/usr/local/netscape/lib
export CLASSPATH=/usr/local/netscape/java/classes

Appendix B - Netscape Crashes

Netscape Navigator 3.01 tends to crash frequently (particularly when using Java) unless one is using an older version of libc.so. Netscape apparently attempts to free() invalid memory pointers. (Either NULL pointers, or pointers to memory which has already been free()ed.) It seems the newer libc's are more intolerant of this behaviour.

These crashing problems seem to be fixed in Communicator 4.03. So this section does not apply if you are running Communicator.

Fixes:

I ran netscape on libc.so.5.0.9, and it seems to work pretty well. (I have it installed in /lib/old/libc.so.5.0.9, and made a symbolic link /usr/local/netscape/lib/libc.so.5 -> /lib/old/libc.so.5.0.9. Then I run netscape with LD_LIBRARY_PATH=/usr/local/netscape/lib.) The cleanest fix seems to be just to preloading an older, less finicky version or the malloc/free code. I have recently switched over to using this kludge - it seems to work too. More details on this scheme can be found here.

The gnumalloc.so I use can be found in gnumalloc.tar.gz. Which was apparently contributed by Doug Ridgeway. Thanks Doug!

Appendix C - ChangeLog

Current version is libmmoss-2.1a.tar.gz

Changes from libmmoss-2.1.tar.gz
Released 6 Jul, 1999.

• The server the signing certificates was on died, so the links to the certificates have been updated. The latest certificate is here. (There have been no changes to the code, and hence no need to upgrade from release 2.1.)

Changes from libmmoss-2.0.tar.gz
Released 14 Jun, 1999.

• Made my code less picky about getting the right number of output fragments (buffers) from the OSS (or ALSA) driver. This should fix and ``java.io.IOException: /dev/audio: number of fragments: requested 2, got 3.'' errors you've been seeing. (Thanks to Reinhard Schulz for the bug report!)
• My new old quasi-bogus signing certificate expired. If you want to avoid the annoying pop-up security alerts, you need to download this latest quasi-bogus certificate.

Changes from libmmoss-1.4a.tar.gz
Released 8 Jun, 1999.

• Added support for EsounD output. This works pretty well for me, but there's still some room for improvement of audio quality, especially if esd is running at a sample rate other than the default value of 44.1 khz. Switching between esd and regular OSS /dev/audio output should be automatic.
• Since adding EsounD support entailed pretty much a whole new implementation of the AudioDevice class, I took the opportunity to do some pretty extensive restructuring/rewriting of the code. It's highly likely that I've introduced some bugs which didn't used to be there. Let me know when you find them.

Changes from libmmoss-1.4.tar.gz
Released 25 May, 1999.

• Reblock InputStream's from 400 bytes up to 512 bytes.

  Sun's sun.audio.AudioDevice reads from it's InputStream's in 400 byte blocks. Libmmoss reads in 512 byte blocks. Some (broken) Java code does not like producing audio in anything but 400 byte blocks (here's an example pointed out by Pete Wyckoff).

Changes from libmmoss-1.3.tar.gz
Released 16 March, 1999.

• Fix bug whereby /dev/audio never got released once opened.

Changes from libmmoss-1.2.tar.gz
Released 6 October, 1998.

• Made the check for getting the correct sample frequency more lenient. Sometimes when a sample rate of 8000hz is requested, one actually gets e.g. 8034hz. This was causing libmmoss to crap out.
• My old quasi-bogus signing certificate expired. If you want to avoid the annoying pop-up security alerts, you need to download this new quasi-bogus certificate.
• Fixed netscape.sh to ensure that LD_LIBRARY_PATH and NPX_PLUGIN_PATH get exported.
• Minor README updates.

Changes from libmmoss-1.1.tar.gz
Released 14 October, 1997.

• Removed the sanity(?) check which was resulting in ``mu-law unsupported'' error messages.
• Figured out how to sign JAR files, so now the annoying popup-dialog when libmmoss loads can be avoided. (You must load and trust this CA certificate if you want to be able to avoid the popup dialog.)
• Rewrite of the Makefile(s), and of the wrapper script.
• Major update of this README.

Changes from libmmoss-0.4.tar.gz
Released 16 June, 1997.

• Now I am primarily supporting Netscape Communicator 4.03. (This is mostly because, for some reason I have not been able to fathom, Java has completely stopped working for me in Navigator 3.01.) I believe this code should still work fine, though, with 3.01.
• The native code now uses Netscape's JRI interface rather than the JDK 1.0.2 JNI interface. Maybe this will minimize some of the funny problems people have been reporting with ``Bad dev'' and ``ioctl(SNDCTL_GETOSPACE)'' errors. Who knows?
• The native code now reports errors using genuine exceptions. This makes the Java code in AudioDevice.java(.in) cleaner, and might make the error messages more interpretable.

Changes from libmmoss-0.02.tar.gz
Released 28 May, 1997.

• Fixes so that EBUSY and ENODEV errors which occur while opening /dev/audio do not permanently do us in. This should alleviate the 'no audio dev' problem that I and others have been experiencing. (It may not fix the problem completely, but at least you shouldn't have to restart Netscape to recover from it anymore.)
• Various other minor efficiency fixes which may or may not help minimize unwanted clicks and belches.