What hardware platforms support the audio and video applications?

Most of the applications have been ported to the DEC 5000, DEC Alpha, HP 9000/700, SGI Indy and Indigo, and Sun SPARCstation. Some applications are also supported on IBM RS/6000 and on Intel 486 platforms running BSD UNIX. No additional hardware is required to receive audio and video on those systems that have audio built in because the rest is done in software. To send audio requires a microphone; to send video requires a camera and video capture device which are only built-in on a few of the systems. For example, the VideoPix card has been used on the SPARC, but is no longer for sale. The newer SunVideo card is supported under Solaris 2.x, but there is no device driver for SunOS 4.1.x (at least not yet). See the descriptions of video applications below for a list of the capture boards supported by each program.

For the camera, any camcorder with a video output will do. The wide-angle range is most important for monitor-top mounting. There is also a small (about 2x2x5 inches) monochrome CCD camera suitable for desktop video conference applications available for around $200 from Howard Enterprises Inc, 545 Calles San Pablo, Camarillo, CA 93102, phone 805-383-7444. Subjectively, it seems to give a picture somewhat less crisp than a typical camcorder, but sufficient for 320x240 resolution software video algorithms. There is also a color model and an infrared one for low light, with an IR LED for illumination.

What operating system support is required?

You can run the audio and video applications point-to-point between two hosts using normal unicast addresses and routing, but to conference with multiple hosts, each host must run an operating system kernel with IP multicast support. IP multicast invokes Ethernet multicast to reach multiple hosts on the same subnet; to link multiple local subnets or to connect to the MBONE you need a multicast router as described above.

IP multicast is included in the standard IRIX kernels for SGI machines, in Solaris 2.3 and later, and in OSF/1 2.0. You can pick up free IP multicast software and add it to AIX 3.2, HP-UX, SunOS 4.1.x and Ultrix as described above. For PC machines running DOS or Windows, IP multicast support is included in the current release of the PCTCP package from FTP Software, but the application programs are still in development. No IP multicast support is available yet for NeXT or Macintosh.

The IP multicast kernel software releases for AIX, HP-UX, SunOS, and Ultrix include a patch for the module in_pcb.c. This patch allows demultiplexing of separate multicast addresses so that multiple copies of vat can be run for different conferences at the same time.

If you run a SunOS 4.1.x kernel, you should make sure that the kernel audio buffer size variable is patched from the standard value of 1024 to be 160 decimal to match the audio packet size for minimum delay. The IP multicast software release includes patched versions of the audio driver modules, but if for some reason you can't use them, you can use adb to patch the kernel as shown below. These instructions are for SunOS 4.1.1 and 4.1.2; change the variable name to amd_bsize for 4.1.3, or Dbri_recv_bsize for the SPARC 10: 

	adb -k -w /vmunix /dev/mem
	audio_79C30_bsize/W 0t160	(to patch the running kernel)
	audio_79C30_bsize?W 0t160	(to patch kernel file on disk)
If the buffer size is incorrect, there will be bad breakup when sound from two sites gets mixed for playback.

What is the data rate produced by the audio and video applications?

The audio coding provided by the built-in audio hardware on most systems produces 64 Kb/s PCM audio, which consumes 68-78 Kb/s on the network with packet overhead. The audio applications implement software compression for reduced data rates (36 Kb/s ADPCM, 17 Kb/s GSM, and 9 Kb/s LPC including overhead).

For the slow-frame-rate video prevalent on the MBONE, the compression, decompression and display are all done in software. The data rate is typically 25-128 Kb/s, with the maximum established by a bandwidth limit slider. Higher data rates may be used with a small TTL to keep the traffic within the local area. Support for hardware compression boards is in development.

Where can I get the audio applications?

The most popular application on the MBONE is the LBL audio tool "vat". A beta release of vat is available by anonymous FTP from ftp.ee.lbl.gov in the directory conferencing/vat where you will find tar files for the various systems supported: 
	decalpha-vat.tar.Z	DEC Alpha
	decmips-vat.tar.Z	DEC 5000
	hp-vat.tar.Z		HP 9000/700
	i386-vat.tar.Z		intel 386/486 BSD
	sgi-vat.tar.Z		SGI Indy, Indigo
	sun-vat.dyn.tar.Z	SPARC, dynamic libraries
	sun-vat.tar.Z		SPARC, static libraries
Included in the vat tar files are a binary and a manual entry. The authors, Van Jacobson and Steve McCanne, say the source will be released "soon". Either SPARC version will run SunOS 4.1.x. The dynamically linked version works better than the statically linked version on Solaris 2 since it will adhere to the name service policy that the user has configured. There is a problem with vat in unicast mode on Solaris 2.3 (it works fine in multicast mode). This will be fixed in the next Solaris release. In the mean time, there is a work around for the problem available by FTP from playground.sun.com in the tar file pub/solaris2/unicast-vat-workaround.tar.

MBone software for Digital Alpha workstations running OSF/1 V2.0 and newer is available at 

	http://chocolate.pa.dec.com/mbone
	ftp://chocolate.pa.dec.com/mbone
In addition, a beta release of both binary and source for the UMass audio tool NEVOT, written by Henning Schulzrinne, is available by anonymous FTP from gaia.cs.umass.edu in the pub/hgschulz/nevot directory (the filename may change from version to version). NEVOT runs on the SPARCstation and on the SGI Indigo and Indy. NEVOT supports both the vat protocol and RTP protocol.

What hardware and software is required to receive video?

The video we used for the July 1992 IETF was the DVC (desktop video conferencing) program from BBN, written by Paul Milazzo and Bob Clements. This program has since become a product, called PictureWindow. Contact picwin-sales@bbn.com for more information.

For the November 1992 IETF and several events since then, we have used two other programs. The first is the "nv" (network video) program from Ron Frederick at Xerox PARC, available from parcftp.xerox.com in the file pub/net-research/nv.tar.Z. An 8-bit visual is recommended to see the full image resolution, but nv also implements dithering of the image for display on 1-bit visuals (monochrome displays). Shared memory will be used if present for reduced processor load, but display to remote X servers is also possible. On the SPARCstation, the VideoPix card is required to originate video. Sources are to available, as are binary versions for the SGI Indigo and DEC 5000 platforms.

Also available from INRIA is the IVS program written by Thierry Turletti and Christian Huitema. It uses a more sophisticated compression algorithm, a software implementation of the H.261 standard. It produces a lower data rate, but because of the processing demands the frame rate is much lower and the delay higher. System requirements: SUN SPARCstation or SGI Indigo, video grabber (VideoPix Card for SPARCstations), video camera, X-Windows with Motif or Tk toolkit. Binaries and sources are available for anonymous ftp from avahi.inria.fr in the file pub/videoconference/ivs.tar.Z or ivs_binary_sparc.tar.Z.