Phone companies do. At least any of those that don’t happen to be Verizon…
I mentioned in my previous post that “IPTV” as a technology for consumers isn’t all that important…from their perspective. On the other hand, it’s a vital technology as competition for consumers’ communication dollars increases.
For years, the cable companies (and more recently, satellite providers) have been the principal sources for video content. They’ve had control of both “live” (often referred to in IPTV vernacular as “linear TV”) and on-demand media. When the Internet (specifically the World Wide Web) began to gain popularity, phone companies and video providers alike decided they needed to be there. The cable folk had a largely analog pipe in the form of their coax infrastructure, while the Telcos had an enormous network of switched twisted-pair connections to virtually every home in the country. Neither was truly prepared for the ‘Web. Both saw an opportunity. Both needed to upgrade their infrastructure to meet the demand.
Cable began the transition to a hybrid fiber-coax configuration and the Docsis standard, while Telcos began earnest development of a mechanism that provided digital transport while protecting their analog voice services, in the form of xDSL. Both succeeded in building a basis for best-effort delivery of Internet data services. Consumers declared “It is good”.
“But wait!” “Why should we stick with simple Internet service when with a little extra work, we can also provide voice service?”, asked the cable companies. Why not do a bit more and provide the “triple play” of voice, video and data so that a consumer will be inclined to get all their communications services from one player? With that, the cable folk began implementing voice services across their IP infrastructure in the form of VoIP. Once they had this capability, they could offer it all in a nice package that a consumer would be motivated to purchase. Hey, when you have a big pipe, you can offer lots of neat stuff. Consumers declared “It is good”.
Phone companies began to sweat it. They were only able to offer voice services and best-effort Internet data capabilities. What to do now? How to offer video to consumers that appears to be the same as traditional cable TV, except use that xDSL/IP infrastructure to deliver it? Why not indeed? Let me tell you why.
xDSL (ADSL, ADSL2+, V.SHDSL, VDSL, VDSL2, etc.) is a constraints-burdened solution for providing digital transport. Given that the un-shielded, twisted pair architecture of the telephone system wasn’t designed for frequencies much above about 4 KHz, it’s pretty hard to push a high-bandwidth signal through a pipe as skinny as that. The various flavors of DSL have been developed to push higher and higher speeds through that same skinny tube. Still, the practical achievable data rates for DSL are limited. In order for telco’s to be capable of providing what appears to be traditional video service, some restrictions had to be understood and dealt with:
- All the possible channels can’t be present “on the wire” at the same time. This implies that a particular channel can only be delivered when the consumer wants it, unlike the old-style cable model where all channels are available at all television sets, all the time.
- Since many households watch more than one channel at a time, the effective bandwidth of the DSL delivery scheme has to be used in the most effective way possible so that all services can run simultaneously without interfering with each other.
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These constraints have driven the current structure of the IPTV services presently available. Specifically:
- IPTV-based video services are designed to deliver only the channels currently being watched. This saves bandwidth of the xDSL delivery. Remember, there’s more going on here than just TV. There’s Internet service, and sometimes VoIP (although that’s less popular with Telco’s just now).
- Video compression is used extensively in order to ensure that any given channel will use the least amount of bandwidth while maintaining the percieved quality of the video and audio.
What really helped the situation for the telco’s was the development of the H.264 (AVC) MPEG codec. It achieves extremely high compression rates while maintaining good video quality, compared to MPEG 2 compression at the same resolution/bit rates, etc. This means a few things:
- More channels can be on the wire at one time, translating to more people being able to watch different channels in the same household, at the same time.
- High definition channels become more likely to be delivered.
There’s always a price to pay when you start squeezing more into less space and this is true for xDSL-delivered video. Next time, we discuss the trade-offs and what this all means to both telco’s and consumers.