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Developed for Davnet under an exclusive contract with InnoMedia, the IP VideoPhone incorporates a 4-inch diagonal, high-quality TFT (thin film transistor) display and a CCD (charge coupled device) camera, which can be unsnapped from the base unit and operated via a supplied 5-foot extension cable. On the back of the base unit, small RCA sockets are available for video in/out and audio in/out for an auxiliary camera or feeding an external monitor or VCR.

There's a COM port to attach a 3.5-foot cable, also supplied, with a DB-9 connection to a computer serial port for software upgrading. Two RJ-45 jacks are provided -- one for connection to the IP network, the other to hub your freestanding PC or laptop.

InnoMedia is evolving its software upgrade and configuration procedures for the VideoPhone. Production versions have simple Web hosting built into the firmware. Simply point a Web browser at the VideoPhone's assigned IP address. It replies with an HTML home page that contains a link to InnoMedia's corporate support site, where you can get the latest product information. There's another link to a password-protected update engine in the phone that will accept file transfers and install new versions of the firmware.

H.323 Interoperability?

I obtained two IP VideoPhones and ran tests using the late-stage beta software InnoMedia deployed in late winter. Just before press time, I obtained the latest software -- version 3.01 -- found in VideoPhones that Davnet started shipping at the end of March. I worked with one unit in my home office in Wisconsin; the other unit was shipped to a colleague who is responsible for advanced development and integration of H.323 applications and systems for the Lawrence Berkeley National Laboratories' Energy Sciences Network (ESnet).

We found that the IP VideoPhone is H.323 version 2-compliant. When necessary, it can function as a voice-only IP telephone. The G.723 audio codec implementation provides good sound quality with VAD (voice-activity detection) and comfort noise generation--features usually found in higher-quality IP phones. VAD reduces the number of packets being sent when no one is talking, yet generates a very low background noise so the line doesn't sound completely dead.

Any H.323 IP end-user device must be able to register with a gatekeeper. The VideoPhone appears to be following the appropriate RAS (registration/access/ security) protocol. A beta problem we discovered in accepting DHCP assignment from a RADvision NGK-100 Gatekeeper was reported to InnoMedia, and it was fixed in the latest software release.

In direct Davnet-Davnet connections, the IP VideoPhones worked very well together. Native video resolution is QCIF (176x144 pixels), which looks good on the base unit's small, tiltable screen. InnoMedia implements the H.263 video algorithm with its own video-processing technology.

Four function buttons are provided on the base unit. Pressing either F1 ("sharper") or F2 ("faster") causes an arrow to move on a quality scale at the bottom of the screen while internal motion estimation and background extraction parameters are changed in the codec. The fastest setting produces refresh rates greater than 15 frames per second. The sharpest setting displays slower frame rates, but picture elements are better defined. Toggling F3, the privacy mode, stops or restarts video transmission to the far end. F4 allows a selection between internal and external video source. You'll also find a mute key on the right of the VideoPhone base unit.

I devoted most of my testing to determining how well the Davnet IP VideoPhone interoperates with other H.323 videoconferencing systems. With a good desktop picturephone, you should be able to call into a corporate videoconferencing network and join a meeting. And InnoMedia notes that this capability is an important goal for the device. However, the performance of even the latest software suggests there's room for improvement.

In tests with a Polycom ViaVideo (version 1.5), I found that the ViaVideo generated full CIF video, and the Davnet could display it. But while negotiating the audio connection, the ViaVideo chose G.711u, and the Davnet settled on G.711a. That's like two speakers being unable to communicate because they use different dialects of a common language.

By contrast, in calls between Davnet and NetMeeting, both sides settled on G.723.1 and provided very good audio. Unfortunately, though the Davnet displayed video from NetMeeting, the NetMeeting PC showed a blank video screen. Something similar happened between the Davnet and a PC running Intel Corp.'s ProShare videoconferencing system. Both sides negotiated very good G.723.1 audio, but video from the Davnet painted only half of one frame on the ProShare, then froze. Video from the ProShare showed up on the Davnet screen in mottled green.

And a Sorenson Vision EnVision videoconferencing system generated QCIF video that appeared on the Davnet screen, but video from the Davnet painted one or two frames, then the EnVision crashed.

Industrywide Problem

Interoperability continues to vex the videoconferencing industry. Unfortunately, H.323 is a very broad standard that provides a variety of options to implementers of audio and video codec algorithms. Systems from different manufacturers can rightfully claim to be H.323-compliant but fail to communicate because of flaws in the complicated negotiation process that takes place during every call setup.

InnoMedia's speed vs. sharpness enhancement for Davnet-Davnet calls is permitted under the standards. But to claim to be H.323-legal, the encoder must generate a bitstream that any H.323 decoder can process without choking. InnoMedia claims that the Davnet VideoPhone generates legal H.263 video bitstreams, and the problems I saw might have been caused by the foreign systems' failure to ignore some of Davenet's negotiation messages; special "faster/sharper" information is traded in H.245 sideband messages. It's still an H.323 fact of life that there's likely to be a lot of finger-pointing among manufacturers when you attempt to make different systems and gatekeepers interoperate.