3G Codecs and IPTV
Mar 17, 2007 8:00 AM
Implementation details
Data rates must be carefully controlled to avoid choking the delivery channel; therefore, CBR (constant bit rate) or capped VBR (variable bit rate) techniques are used. Each technique guarantees that the maximum capacity of the delivery channel will never be exceeded. Limiting bit rates, however, can introduce the potential for artifacts when coding complex video scenes.
Program assembly is facilitated via MPEG PSI (Program Specific Information) rather than ATSC PSIP. PATs (Program Allocation Tables), PMTs (Program Map Tables) and CATs (Conditional Access Tables) are simpler to implement and consume less bandwidth than PSIP, and for this reason, they are better suited for DTV over the Internet.
IPTV consortiums
Implementing an IPTV system is a huge undertaking. As a result, aggregation and distribution of content requires cooperation among multiple players. Each member of a consortium provides its expertise, be it the space segment, compression technology or customer management software, to create a one-stop shop for those seeking to roll out IPTV services.
One example is the SES Americom (http://www.ip-prime.tv/ipprime/index.php) IPTV system, IP-PRIME. The system has been enabled by a partnership consisting of Globecomm, Harmonic, NDS, Scientific-Atlanta, International Datacasting and Siemens. The cooperative effort has created an end-to-end service with encoder, middleware, scrambling/descrambling, content protection, conditional access, satellite receivers, service management and integration services.
Another major player, Cisco's NGN (Next-Generation Network) also offers an end-to-end IPTV service. The service is targeting rural areas with more than 290 channels, including 20 HD services, and uses AVC encoding for video compression. Features include Scientific Atlanta's ROSA system management and AMC-9, a C-band satellite.
Real-world numbers
So, how has IPTV fared in real-world deployment? The numbers are cloudy because the service is just taking off.
AT&T U-verse rosily predicted passing 18 million homes, but faced a reality check when the envisioned number was reduced to 8 million. Some sources state that AT&T's Q4 report cited 3,000 subscribers.
The largest IPTV implementation so far is in Hong Kong, where PCCW claims 650,000 subscribers. During the next five years, IPTV is expected to grow to 80 million subscribers worldwide from about 6 million IPTV households today.
The future
Interactivity is a given with IPTV and may be the application that captures consumer attention. All the technological pieces are in place. Perhaps the time is finally right for the long-awaited convergence of the PC and TV.
Traditional OTA broadcasters are in a winning position. IP distribution of DTV programming is yet another distribution channel that, properly managed, can produce additional revenue. Whether this is an opportunity or problem depends on one's personal viewpoint.
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