Nokia is boasting about a significant deployment of its 5910 Video Service Appliance at Swisscom for its TV 2.0 installation. The system is usually installed in environments where either there is a high degree of network jitter or lost packets, and it speeds up Channel Change. It may also help where UHD TV channels are delivered under constrained conditions.
This is a bit like an ETSI standard equivalent of the D server in the original Microsoft Mediaroom set up, which facilitated fast channel change, although this does a lot more.
The fast channel change solution of Microsoft came about because in SD and HD, there were 12 or 15 frame GOPs (or groups of pictures), between each I-Frame. At 30 fps that meant up to half a second of video was sent in an IPTV multicast before the next I-Frame was delivered. This in turn meant that anyone pressing a channel change button on the remote had to wait until the next I-Frame came. So Microsoft issued a “join multicast” instruction, but also fetched an older I-frame from a buffer, in ultra-quick time, then scheduled the new frames in, once they could be rendered with reference to the I-Frame.
Mediaroom reached a channel change of around 200 milliseconds, worst case, and was compared in its heyday against a 3 to 4 second cable TV channel change. But very few IPTV customers outside of Mediaroom, ever installed anything like this. We know that Cisco came up with a pre-standard version in its Videoscape range, but we cannot point you to a single client who bought it.
Another of the benefits of this type of server is that during a multicast, if a packet resend request goes all the way back to the multicast router, then the entire network of thousands of homes, gets the packet resend. Which is why packet resend is not enabled in a multicast. This server intercepts these requests and sends a replacement only to the TV which requires that packet resend, finding the packet in its rotating buffer.
The Alcatel Lucent or rather Nokia 5910 goes further, and is used as a concentrator for localized advertising insertion too, whipping out frames with adverts in, and replacing them with locally mandated adverts.
Swisscom was originally a Mediaroom customer and so has locations within its network for these servers, but now it no longer uses Mediaroom, so needed an ETSI standardized version of the same. Another reason for using these servers in the run up to introducing UHD, is that when you use a codec like HEVC, the GOP length (gap between each I-Frame) gets longer in order to preserve bandwidth, but that can lead to a much larger channel change problem, unless you have this type of box in place. It will be interesting to see if many other IPTV customers adopt this approach as they implement UHD. We suspect they will.
Swisscom claims that with UHD, the 5910 will reduce the time to change channels to under a second. We would have thought it would be faster than that. The system is middleware independent, works across any last mile access technology and with any DRM, the company said. It is our understanding that Swisscom already used equivalent channel change servers from Alcatel in the past, when it had Mediaroom.
The system will be installed centrally in Swisscom’s two head-end data centers and made available to Swisscom’s entire subscriber base.