Cablevision, AT&T in Beef over IPTV Bitrates
A program access rift between Cablevision and AT&T over whether AT&T’s U-verse service can carry the cable operator’s regional sports networks in Connecticut highlights a tension between IPTV providers and TV programmers in regard to video compression technologies. Among Cablevision’s main gripes about U-verse is the low bitrate at which AT&T delivers content, a recent FCC filing shows. Cablevision’s Rainbow programming unit provides programming to distributors in MPEG-2 format, long the cable industry standard. It worries that if AT&T decodes that signal, re-encoding in the more- advanced MPEG-4 format, too much data will be lost, degrading picture quality. AT&T has claimed that Cablevision is withholding its programming available to squelch competition. Vendors said the dispute also raises network management issues that IPTV service providers face.
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AT&T never sends standard definition programming above 1.8 Mbps, Cablevision said in a recent status report on its talks with the carrier. AT&T told Cablevision it can’t go higher due to most favored nation clauses in contracts with other programmers, among other reasons, the report shows. AT&T uses a variable bitrate system, allowing it, when content permits, to send less information, easing stress on its network. Live sports events and other motion-intensive programming demands higher bitrates than does relatively static material like talking-head news. Cablevision doubts that 1.8 Mbps suffices to show its sports programming in high enough quality, it said.
More alarming is that AT&T may trim its bitrate to fit other network traffic such as VoIP and other activity in a subscriber’s home, Cablevision said. For instance, if a U- verse household has multiple set-top boxes simultaneously tuned to different channels, the multiple streams entering the house will be “competing with one another for bandwidth (as well as with other network activities such as VoIP and network control), thereby lowering the peak value of the variable bit rate of the streams and amplifying the quality concerns,” Cablevision said.
Sending sports programming at 1.8 Mbps is “pushing the limits of where the technology is right now,” said Matthew Goldman, Tandberg TV vice president of technology. “It might not be in a year, but it is now. 1.8 is not impossible. You're definitely being aggressive at 1.8 and anybody that’s worth their salt in doing network planning knows the challenge.” But if network managers have done their homework, subscribers might not notice picture problems, even at lower bitrates, he said. “If the 1.8 Mbps cap that AT&T put in is a reasonable cap, then you won’t see any glitches different than what you would see on cable, for example.”
Advances in MPEG-4 support aggressive compression, said Paul Connolly, vice president of business development for Scientific-Atlanta. “We have come down the learning curve more rapidly for MPEG-4 compression improvements than anyone would have predicted 2 years ago,” he said.
Next-generation codecs are rumored, but it probably will be five years before industry ditches MPEG-4/AVC for something radically different, he said. “As far as changing technology from MPEG-4 to the next system, it’s a long way off. There are some closed-loop propriety systems available today, but you need to have the coding technology universally accepted to get the chip prices down,” he said. “You're not going to keep uprooting compression systems every two years with the investment in set-top boxes.”
So programmers and distributors may continue to haggle over bitrates as they work out carriage deals. “This is an issue that the programmers and distributors must address together,” said Mike Donovan, senior vice president of engineering for Scripps Networks. “We are working with our distribution partners to understand their system architectures and develop a solution that ensures the quality of the product delivered to the customer. We don’t believe that requiring a commitment for a specific bit rate is the answer today because the technology is changing so fast.”
Ultimately, programmers’ and IPTV carriers’ goals are aligned; both want to deliver superior quality, Connolly said. “You'll always see that dynamic between the content owner wanting to make sure the programming is delivered to the end user in the best manner and the operator that’s trying to build an efficient network,” he said. “But I don’t think any operator wants to deliver sub-quality video.”