Internet protocol television was one of the hot topics at the ITU Telecom World conference in Hong Kong. Cisco announced what it described as Visual Quality Experience technology, designed to improve the viewing experience for video services delivered over data networks.
The Cisco system enables network-based rapid channel-change and video error repair. Microsoft has already made much of the ‘instant channel change’ capabilities of its video solution and it has come to be seen as a differentiating feature.
“Working in conjunction with set-top boxes to detect and accelerate channel-change requests, the Cisco VQE rapid channel-change technology reduces channel-change times from several seconds to less than one second by initiating video streams less than 100 milliseconds after a request is made,” says the Cisco press release.
This conveniently ignores any video decoding delays that typically represent the majority of any latency in changing channels.
The release quotes a representative of Telecom Italia saying: “A one to two second delay is unacceptable to anyone who is channel surfing and would be a significant barrier to adoption for many.”
The reality is that such delays are already experienced by viewers of digital broadcasts and are rarely cited as an objection by viewers. A fast and easily navigated electronic programme guide is arguably much more important once viewers are able to actively select channels and programmes rather than simply zapping between them.
The Cisco technology, which will be integrated into their intelligent network routers, will also apparently work with set-top boxes to detect and repair missing data packets within 100 milliseconds. Retransmission of lost or corrupt data is a standard approach in connected networks but it can be a problem with real-time media.
Digital broadcasting typically deals with data loss as a fact of life in an unreliable transmission medium by introducing a degree of redundancy in the signal, which requires more bandwidth. Such forward error correction techniques are available for delivering video over data networks, but it appears that they are currently rarely used as they require more network capacity.
Another feature that Cisco says will “improve the quality of video service and video experience” is known as video connection admission control. “This helps ensure a high-quality viewing experience even when demand for video results in network oversubscription, a scenario that will become increasingly common as IPTV systems are more broadly deployed and subscriber numbers increase.”
Effectively this seems to mean that viewers will get a busy signal when the system is overloaded. This may be preferable to a degraded service, but it is far from clear why technology or service providers might believe that this is an acceptable user experience.
Cisco says its will provide the network intelligence required to deliver “the most reliable and scalable Video 2.0 experiences”.
Building more intelligence into the network may well offer the opportunity to deliver a new generation of television and video experiences, but service providers may need to come up with more than fast channel changing and reliable video it they are to attract subscribers from existing forms of video distribution.