VI.

This chapter discusses typical videoconferencing software and hardware that can be used to deliver distance learning via videoconferencing from a desktop computer over an IP-based network. This chapter does not endorse any particular software application(s), but is merely providing some examples of common tools currently available. This chapter also provides the recommended standards when employing desktop videoconferencing.

Although most of the newer routers and switches are configured to support IP multicast, many of them are, by default, not enabled. Also, many current software applications are unicast and must also be modified to interface with the multicasting capabilities of TCP/IP stacks, which in turn, join and leave multicast groups by using IGMP [Hurwicz, 97]. Because companies realize that there is great potential in videoconferencing, these issues have not inhibited application developers from eagerly creating new products.

Bandwidth and picture quality is still a major impediment, but other barriers like standardization, costs, and installation costs continue to decrease. Microsoft has embedded its collaboration tool, NetMeeting, in its free Internet Explorer 4.0 browser. Netscape Communicator 4.0, which is also free, packages an analogous tool, Netscape Conference. Microsoft also has released a UNIX version of Internet Explorer 4.0. The MBone also used uses free videoconferencing desktop applications (vic, vat, sdr, wb) that are proven and reliable. Unfortunately, many of the commercial desktop applications, which are PC based, are not fully compatible with the MBone tools, which are mostly UNIX based.

Delivering synchronous/asynchronous video and audio streams to sea not only requires a network architecture, but it also requires software tools that are capable of providing quality content to the student. Even so, quality content delivery does not replace the need for occasional student/instructor collaboration. Today’s desktop videoconferencing tools can generally be broken down into two categories. First are standards-based collaboration applications, which provide complete information-sharing solutions that span the spectrum from one-to-one to fully interactive meetings. Secondly, there are streaming applications that broadly distribute one-way, live or stored presentations. Desktop collaborating applications enable users to communicate with a small number of others, such as for desktop videoconferencing. Streaming applications are much more scalable, making it possible to reach a virtually unlimited audience.

Streaming applications will generally have both client and server software, whereas collaboration applications can be client-to-client. To inititalize multipoint sessions, collaborative application users register their contact information with a location server. Four11 and Microsoft’s Internet Location Server (ILS) are two examples. These servers are based upon Lightweight Directory Access Protocol (LDAP).

Because audio is the most critical and sensitive aspect of videoconferencing, applications should provide features that allow audio adjustments to compensate for non-guaranteed bandwidth. Applications must support different audio codecs in order to allocate certain amounts of the data stream for different bandwidths. Chat room software can be used as an option when voice and video are bandwidth constrained. The ability to tune audio during transmission, and embedded Forward Error Correction (FEC) or redundancy schemes, used in CU-SeeME and the MBone's rat tool, can help minimize poor audio reception.

Desktop videoconferencing collaboration applications also need a combination of document management capabilities, such as file sharing, white board, and snapshot tools, which allow users to capture whole windows or parts of windows for cutting and pasting to the whiteboard. Standard e-mail applications can be used for administrative purposes, such as setting up time for point-to-point conferencing when additional help is required.

Multicasting videoconferencing applications use basically a straightforward extension to BSD 4.3 Berkley Socket API, which is supported by operating systems such as UNIX, and Windows 95 and NT. As these API’s become cross-platform capable, and more readily supported by Winsock 2, they will be ready for widespread use on PC’s, running OS’s such as Windows.

H.323 and H.324, T.120, along with multicast protocols, such as IGMP, RTP, RTCP, and RSVP make up the primary standards for desktop videoconferencing systems. As an extension of H.320, H.323 addresses multipoint videoconferencing over ISDN, POTS, as well as LANs and the Internet. H.324 is the standard for real-time multimedia standards over POTS. When using application from different vendors, ensure that each completely implements the standards it claims. For example Microsoft NetMeeting and Netscape Conference are both "H.323 compliant," but they do not have any common audio codecs, rendering them unable to talk with each other. Even with these misinterpretations, the standards-based support and deploying an application base required for most desktop videoconferencing is no longer an inhibitor. As in the past, network bandwidth and interoperability across different platforms are still the major problems. Dial-up with modems over POTS still continues to be a choke point for delivering and receiving videoconferencing. As H.324 matures, manufacturers will begin to build more H.324 compliant chip sets into hardware. As of now, H.324 is acceptable for point-to-point collaboration, but not for supporting IP multicast.

Although the ITU-T has provided the baseline codec standards for videoconferencing there are several de facto standards that have emerged. Microsoft Video for Windows and Apple QuickTime are common video codecs. QuickTime is compatible with both Windows and Macintosh environments and has been accepted by ITU-T as the basis for MPEG-4. The use of hardware codecs can alleviate some of the CPU usage, but today’s multimedia capable processors are more than capable.

One of the first companies to market a product fully based upon IETF standards that relate to real-time video and audio streams, and ITU-T standards for data compression and decompression was Precept Software. Its Flashware Server software and IP/TV viewer client were initially available for Wintel based systems. Because of the implementation nonproprietary standards, this product can receive MBone group sessions, giving it the capability to interoperate with UNIX platforms. Until more companies adopt universal standards, this is one of the few options for cross-platform capability between UNIX and PC users.

	LAN/WAN,Internet, H.323	POTS, H.324
Video	H.261,H.263	H.261,H.263
Audio	G.711,G.7.22,G.728, Full-Duplex	G.723,Full-Duplex
Whiteboard	T.120,JPEG,GIF TIFF, Postscript, Still Frame Capture, File Transfer	T.120, JPEG, GIF, TIFF,Postscript, Still FrameCapture, File Transfer
Additional Features	Chat Functions, Application Sharing	Chat Functions, Application Sharing
Multicasting	RTP, RTCP, (RSVP,RTSP when adopted),Multiple Simultaneous Sessions
Controls	BW Controls(Frame- Rate, Image Size)	BW Controls
Asynchronous Support	Yes	Yes
Additional Support	Firewall Configuration,Trial Copies for testing	Trial Copies for testing
Router Support	MOSPF, PIM

Today’s desktop computers provide most of the hardware components needed for videoconferencing. A good camera and video capture card, which can cost as little as $200, is all of the upgrading that is normally required. This is a markedly low price in comparison to roll-about and room-based systems. The release of its newer, faster multimedia based processors is sealing the fate of expensive hardware codecs. This is the recommended desktop system hardware requirement to support desktop videoconferencing:

Cameras that connect to video capture boards are recommended. Parallel cameras are unacceptable because of inadequate data throughput, and because they require excessive CPU cycle time.

The ITU-T and IETF standards will likely gain broad acceptance since they are based upon videoconferencing over the commonly existing network architectures. In order for videoconferencing to gain full acceptance, H.320, H.323 and H.324 must work together integrated applications.

Although desktop videoconferencing is becoming more capable, the frame rates and and small picture size of streaming videoconferencing applications are still lacking. If used in conjunction with collaborative software such as whiteboards, shared application and shared control, there is adequate functionality to conduct meaningful learning.