SIP videophones fall short of the Interop mark

Our testing of five videophone products - softphones from Nortel and Xten (on Macintosh and Windows platforms) and hard phones from InnoMedia and Leadtek - was not a pretty picture.

As with our other SIP testing, basic connectivity for voice calls between the videophones worked well. But we ran into substantial problems when we tried to use the video features.

Of the 25 cases we tested, only six of them gave acceptable video quality between phones, specifically only the single-vendor phone-to-phone calls. Going between vendor devices - despite having a completely switched 100M bit/sec network - was a recipe for complete failure, only one-way video, or just plain horrible video quality. For example, when connecting between the Xten and Leadtek videophones, we got a two-way video connection but the quality of the video at high speeds was so poor that we had to reduce bandwidth to 128K bit/sec or less to even see semi-continuous motion. Videophones turned into a Catch-22: Setting speed up to 512K bit/sec, high enough for acceptable video quality, locked up and crashed phones or kept them from making connections at all. Turning the speed down gave us better interoperability, but reduced the video to something akin to Neil Armstrong's 1969 moon walk.

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Our testing of five videophone products - softphones from Nortel and Xten (on Macintosh and Windows platforms) and hard phones from InnoMedia and Leadtek - was not a pretty picture.

As with our other SIP testing, basic connectivity for voice calls between the videophones worked well. But we ran into substantial problems when we tried to use the video features.

Of the 25 cases we tested, only six of them gave acceptable video quality between phones, specifically only the single-vendor phone-to-phone calls. Going between vendor devices - despite having a completely switched 100M bit/sec network - was a recipe for complete failure, only one-way video, or just plain horrible video quality. For example, when connecting between the Xten and Leadtek videophones, we got a two-way video connection but the quality of the video at high speeds was so poor that we had to reduce bandwidth to 128K bit/sec or less to even see semi-continuous motion. Videophones turned into a Catch-22: Setting speed up to 512K bit/sec, high enough for acceptable video quality, locked up and crashed phones or kept them from making connections at all. Turning the speed down gave us better interoperability, but reduced the video to something akin to Neil Armstrong's 1969 moon walk.

A closer analysis of the SIP protocol messages flying between the phones showed that different vendors were picking very different parameters for their videostreams - and most of these parameters were not under the control of the end user

Cool SIP video gadgets

But lack of SIP interoperability does not preclude these phones from being fun gadgets to have on your desk. Here is a list:

• Pick up your iSight or USB camera and you're rolling with Xten's eyeBeam softphone. This lets you make calls to any Internet-connected SIP device.
• It looks like a cell phone, but it's not; the UTStarcom Wi-Fi phone is compact yet has a full set of SIP features.
• Although the Azatel Wi-Fi SIP phone was running beta code, people will be crawling all over each other for the large, clear color screen.
• The Zultys 4x5 has one extremely cool feature: compatibility with Bluetooth headsets.

Return to "Advanced SIP interoperability is slow in the making"

Read more about voip & convergence in Network World's VoIP & Convergence section.