RealVideo tries its hand at videoconferencing -

If you can't afford dedicated videoconferencing, the next best thing might be Progressive
Networks' RealVideo 4.0.

This client-server system streams audio and video over TCP/IP networks. With
28.8-kilobit/sec modems to do the transmitting, RealVideo can display a quality,
10-frame/sec, small-screen video. It really shines on 56-kilobit/sec and faster networks.

RealVideo pulls this off with video coder-decoder algorithms that play video clips as
fast as your system can download. It works with the company's proprietary RealVideo
Standard, a discrete cosine transform algorithm, or the RealVideo Fractal codec from
Iterated Systems Inc. of Atlanta.

RealVideo must use low resolution and frame rates. It compensates for this by analyzing
the network stream and adjusting for lost packets.

To get the display from server to client, RealVideo supports the Real-Time Streaming
Protocol (RTSP), proposed to the Internet Engineering Task Force as an open standard by
Netscape Communications Corp. and others.

Some vendors oppose RTSP as a move to pre-empt the real-time audio and video
multicasting market. But for now, RTSP is the de facto multimedia streaming standard for
TCP/IP networks.

On the client side, users can download the RealPlayer 4.0 viewer free from
Progressive's World Wide Web site at http://www.real.com.
  To get more control over the video and audio reception, you'll have to pay $29.95
for the RealPlayer Plus viewer.

Either way, the player requires 2M free on the hard drive, 16M of RAM and a TCP/IP
network connection, plus Microsoft Windows 95 or Windows NT 3.51 or 4.0. There's another
version for Apple Power Macintosh.

Practically speaking, any machine that runs the player should have at least 32M RAM and
a 100-MHz or faster processor. RealVideo is real demanding. If you have the equipment,
though, RealVideo works well.

You can view only RealVideo-encoded materials--not Motion Picture Experts Group or
Apple QuickTime video. That's not too limiting, because many Internet sites have adopted
RealVideo for their audio and video offerings. The video isn't going to knock your socks
off. The audio more approaches CD sound quality.

At slower speeds, video and audio components do well. When the program gets stuck with
a low-speed connection, or when network delays make a connection slow, the program
downloads more of an audio or video clip before playing it back. The result is
better-quality multimedia than you might expect.

On the server side, Progressive Networks offers two choices: ProSolution and EasyStart.
Each server package can run under IBM AIX, Digital Unix, FreeBSD, Hewlett-Packard HP-UX,
Silicon Graphics Irix, Linux, SunSoft Solaris or NT. In theory, you need only the minimum
memory requirements for each OS plus 20K per RealAudio and 60K per RealVideo session.

However, in practice you can expect the server to take at least 32M RAM. If you plan on
streaming more than five feeds at once, you'll need more RAM and a dedicated system. Even
if your plans are small, never install the server software on an even moderately loaded
box. RealServers do remarkably well at husbanding hardware resources, but they can't
perform miracles.

If you plan to broadcast RealVideo to the Internet, you'll want at least a fractional
T1 at your disposal. My recommendation would be to start with a 384-kilobit/sec
connection. For serious transmission, consider a full T1.

One thing you don't have to worry about is the effect of firewalls on transmission of
the multicasts. Most commercial firewalls now support the Real standards. If your firewall
doesn't, you can configure a packet-filtering firewall to allow multicast transmissions.
Progressive makes source code available for building transparent or application-level
firewall proxies.

The differences between the two server products are primarily in support and
expandability. With the ProSolution server line, you get more technical support and the
ability to multicast to up to 400 simultaneous users.

On the EasyStart side, you get only e-mail support and a maximum of 60 users. EasyStart
also has fewer options. For example, you can narrowcast only to a certain domain, range of
IP addresses or selected addresses.

On the Pro side, you get bundled RealAudio/Video Encoders. You can download Encoders
for EasyStart, but they're not packaged with the server. Last but not least, Pro servers
come with server management and audio-editing and translation programs.

For a would-be Net broadcaster, the Pro package has everything you need to go into
production out of the box. The EasyStart is the harder start of the two, but its freeware
version does give you a chance to try out Real broadcasting before buying anything.

The player will be a useful, almost necessary, addition to every Internet user's
collection of programs. Real servers, however, shine only when they're used by an
organization with a clear message to present. If your agency has a constant stream of
projects where narrowband or multicast audio or video would help get the message across,
then investing in such a server makes sense.

Steven J. Vaughan-Nichols is a computer journalist in Lanham, Md.