An industry group is seeking to address perceived concerns over channel changing delays associated with internet protocol television services. It comes in response to Microsoft promoting fast channel changing as a key benefit of its IPTV software platform, but it remains unclear to what extent this is a real issue.

The Internet Streaming Media Alliance, which promotes standards-based systems, has identified fast channel change as “a vital quality of experience issue potentially affecting consumer adoption of IPTV”.

Whether or not this is a real issue, there is no doubt that Microsoft, which has a proprietary ‘patent pending’ approach to achieving fast channel changing, has consistently identified this as a key feature of its platform.

In usability testing, Microsoft has found that their ‘instantaneous channel change’ feature can improve user perception of other aspects of application performance.

This may well be the case, but after a decade of experience with digital television, channel changing time has rarely been raised by viewers as a major problem. After all, viewers are mainly concerned with programming.

“Channel hopping” or “zapping” is generally a symptom of an irritation at lack of sufficiently engaging programming, a response to interruption by advertising, or a function of a poor programme guide.

In a world of digital video recorders and video on demand, viewers are increasingly selective in their viewing choices, rather than idly cycling through linear channels. Navigation, discovery and search are therefore of key importance, but channel changing is only one aspect of this.

Nevertheless, ISMA has begun work on a new specification addressing instantaneous and reliable channel acquisition and continues to solicit industry input on the topic. They have produced a paper on ‘Fast Channel Changing in RTP’ which is available from their web site and provides an excellent introduction to the technical issues involved and ways in which latencies may be reduced.

RTP, Real-time Transport Protocol, is a foundation of internet protocol television. As Nikolaus Farber of the Fraunhofer Institute and the technical chair of the ISMA points out, channel changing may be less of an issue than some have suggested.

“There is a general myth in the industry that RTP channel change is slow and erratic in principle,” he said. “But with the correct deployment, RTP is one of the most stable and effective technologies for IPTV, including fast and accurate channel tune-in.”

The initiative looks at the coding, transport and network layers, and proposes solutions based on correct RTP usage, RTP extension headers and distributed edge servers to support fast channel selection.