US error correction leader Digital Fountain has landed a large tier 2 European telco in Tele2 Netherlands, its second major IPTV customer, to use its Toughstream forward error correction system for IPTV. Digital Fountain won its first IPTV customer back in 2004 when it first introduced commercial products which used its Raptor codes which were incorporated into Sumitomo Electric StreamCruiser IP set-top box for NTT’s Theater video-on-demand service.
The ToughStream system which Tele2 has opted for is a full solution including software and servers from Italy’s Neptuny all pre-configured to fit into existing IPTV services. Digital Fountain only introduced the ToughStream server at last year’s IBC, and built it with high availability and technology from Milan based Neptuny on standard Linux servers. After prolonged trials ToughStream is now live on Tele2’s IPTV network.
Digital Fountain told us last year that High Definition services in particular were having issues with lost packets, since the data volumes were so much higher, and that it was getting a call from IPTV operators within weeks of them switching on HD services.
There are only a handful of ways to deal with packet loss in IPTV, which can be very destructive, especially if it affects one of the core reference frames called an I-Frame. Many systems like Microsoft’s Mediaroom and Cicso’s VQE, prefer to resend lost packets. This increases buffer size at the set top and leads to more servers in the network and some hand-coding to make it happen. So it can be expensive. The original Fastweb IPTV service in Italy, a long standing reference platform for others in Europe, had packet resends carried out in high level application code.
Packet resends can’t be used in a multicast, because a lost packet for one set top will mean the packet is retransmitted to everyone, and since most packet losses occur once the streams separate after the DSLAM, that would mean resending virtually every packet, with the resulting chaos. So they all use multicast and then some kind of unicast back channel to deal with the resends.
Digital Fountain’s Raptor codes use an outer code to transform packets of data, and effectively a piece of each packet is sent in multiple other packets so that packet reconstruction is easily carried out. The codes are linear so that to recreate 20% of missing or corrupted packets, the system needs to send 120% of the original number packets, 5% needs 105%, and so on.
Digital Fountain has already been selected as the FEC of choice for DVB-H and MBMS, two mobile TV standards, and is used on Satellite Radio in the US, and it is now being pushed into IPTV.
Being very early to IPTV NTT ended up with a lot of quality problems, and gave the codes a test in their Sumitomo set top, back in 2004. The company found that even when packet loss was quite low, viewing times doubled when the Raptor FEC was used.
In the Netherlands Tele2 found its IPTV had interference created by the electromagnetic interference from the tram system, and its suppliers had never considered this in their designs.
The Digital Fountain Raptor codes can be arranged to correct a different amount of loss for each line that is linked to a DSLAM, without change to the set top software, with an automatic setting at the Toughstream server. In this way the FEC can be applied to meet the packet loss expectations of individual lines. In the end Tele2 decided not to opt for this approach and have installed a system that can cope with a 9% packet loss, which suits their system.
The Tele2 IPTV system goes out to roughly 100,000 homes, and despite KPN saying that it has 414,000 Pay TV customers, up 77,000 last quarter, Tele2 reckons that because KPN lumps its DVB-T Pay TV service in with its IPTV service numbers, that in fact it is the largest IPTV system in The Netherlands, a country dominated by cable TV offerings, especially from UPC.
But like NTT, it has a pretty non-standard style of IPTV, built by Samsung, with proprietary Korean middleware and set top, and a content feed from a national shared head end. So it couldn’t address the FEC issue at the head end which it doesn’t control, only from the DSLAM downwards in the network, making the Digital Fountain approach a natural choice to attack the high churn rates that it was experiencing, believed to be above 20% per annum.
Alex Hayward, Director of IPTV at Digital Fountain told Faultline, ‘The customers service calls fell by 50% once we installed the system, and the churn rate has also fallen dramatically,’ be he couldn’t go into the Tele2 numbers in any details. Tele2 now believes that it is on track to ramp its growth rate to 35,000 per quarter.