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Optoelectronics/Displays??

IPTV rollouts put premium on codec flexibility

Posted: 03 Apr 2006 ?? ?Print Version ?Bookmark and Share

Keywords:michael stich? charlie gonsalves? texas instruments? ti? home networking?

Telcos are marshalling their forces for a battle with cable-TV providers that will shape the landscape of television, high-speed Internet and telephone service in the next decade. Cable multiple service operators (MSOs) have scored an enormous hit by using their hybrid fiber/coaxial cable infrastructures and leased lines to deliver triple-play video, cable-modem-based data services and voice services to customers. Now, the telcos are responding by beefing up their DSL infrastructures and using bandwidth-efficient video codecs to add IPTV, a killer application for ubiquitous broadband penetration, to provide their own triple play. A key prerequisite to their success will be the delivery of multiple HDTV streams to channel-hungry US consumers. This in turn requires next-generation STBs that can support today's MPEG-2 codec and more advanced codecs such as H.264 and VC-1 that increase bandwidth efficiency.

Conserving bandwidth
One of the most attractive features of IPTV is that it overcomes cable's limitation of having to deliver every available channel to every customer. This limitation means that MSOs are continually limited by their network's bandwidth capability, forcing them to drop a channel every time they add a new one. IPTV solves this problem by using packet-based Internet technology to stream only the channels that the viewer is currently watching, conserving network bandwidth and enabling various new programming options. IPTV enables on-demand viewing and makes it possible to embed a limitless array of information inside the video stream. IPTV is also the killer app for ubiquitous broadband penetration, since without it, broadband market penetration is limited to households with PCs.

Selecting technologies
Because TV can be found in nearly every home, IPTV can enable telcos to generate new revenue from customers connected to their broadband networks. Nevertheless, before they can realize those revenues, telcos have to select the appropriate technologies to support IPTV. Telcos can use xDSL/ADSL 2+ or UDSL to transmit IPTV triple-play content to their customers. The content is delivered to a home gateway or STB, which is likely to feed the content it receives from the DSL pipe to a home-networking device that could be wired, wireless or a combination of both.

As broadband moves to a mass-market multiservice model, STBs are evolving as much more powerful multiservice devices. At the higher end, they are evolving into residential gateways, connecting a wide range of household devices through a single broadband connection. Residential gateways are characterized by functionality such as dynamic routing, firewalls and support for multiple home-networking technologies. Personal video recorder (PVR) functionality is also beginning to appear in higher-end STBs. As this trend develops, features such as DVD-RW and the ability to transfer content to portable media players (PMPs) will become important. Another important consideration in STBs will be the ability to support upstream and downstream data flow to enable applications such as videophones and security.

Telcos must determine if they want to use a distributed or centralized hard-drive architecture to deliver PVR functions to all the TVs in a home. In the distributed method, a hard drive could be located at every TV (or each TV's STB) in the home. Using the centralized method, the PVR function could be allocated in a master IP STB's hard drive, which could be used to serve all the TVs in the house. Regardless of how PVR is implemented at home, QoS, security/authentication and content protection must be supported to each customer appliance attached to the home-networking gateway.

Piracy, DRM and the end-user experience are also critical issues that must be addressed before IPTV can succeed. But even with the construction of advanced fiber-to-the-neighborhood (FTTN) and fiber-to-the-premises (FTTP) networks, the most critical issue will be providing the bandwidth needed to support multiple IPTV channels that most customers will demand. While the telcos' new networks provide a very fat pipe, HDTV and SDTV can quickly fill it.

HDTV content requires 20Mbps, while SDTV content requires 4Mbps of bandwidth when delivered in MPEG-2. With many households expected to demand three or four channels of HDTV content, telcos need to find ways to deliver content to their customers efficiently. Fortunately, advanced codecs such as H.264 format of MPEG-4 part 10 and VC-1 offer 2.5-3x bandwidth-efficiency improvement over traditional MPEG-2 codecs.

Delivery range
Another factor used to determine the bandwidth needs of end-users on an IPTV triple-play network is the number of channels and the distance between end-users' locations and the digital subscriber line access multiplexer (DSLAM) or DSL remote terminal. How the network is implemented helps determine which codec will best serve the objectives of the operator. The benefits of reduced bandwidth requirements include the ability to deliver service to more households. There are different bandwidth/distance thresholds for different scenarios. Simply put, advanced codecs are preferred in IPTV networks because they cost-effectively extend the reach of those networks. Greater reach increases the number of potential customers from which telcos can collect new revenues.

VC-1 and H.264 are currently engaged in a format war. It appears that the MPEG-4 part 10 standard has gained a significant lead, since it was officially sanctioned by the ISO in 2004, while VC-1 has only recently reached the final committee draft stage at the Society of Motion Picture and Television Engineers. However, the potential exists for VC-1 to rapidly close the gap. Since VC-1 is based on the Windows Media 9 compression system, there is less room for disputes over interpretations of specifications than what existed with MPEG-4. Another important factor in VC-1's favor is that many telcos have announced support for Microsoft's IPTV platform. While H.264 can be deployed over the Microsoft IPTV platform, there will be a strong inclination for telcos that have adopted Microsoft IPTV to implement a completely integrated Microsoft solution. The process for ensuring interoperability with VC-1 is also potentially simpler because Microsoft is the final arbiter of the standard, as opposed to H.264, which is subject to different interpretations by many suppliers.

Performance benchmarks
Obviously, system developers would like to have as much information as possible about how DSPs and other processing elements can perform H.264/MPEG-4 compression and decompression. But the success of the new standard in improving performance is also the source of difficulty in providing benchmarks for it.

As the pace quickens toward commercial IPTV implementation on a large scale, the pressure intensifies on equipment suppliers to deliver affordable next-generation STBs. At the same time, however, the industry's inability to agree on which of the different advanced codecs will become the dominant technology for IPTV systems introduces an element of caution. The onus is clearly on STB manufacturers to quickly bring to market highly flexible platforms that can be quickly and inexpensively upgradedespecially as the market stabilizes and grows behind fewer and more robust video standards.

Michael Stich
Director of Service Provider Strategy, DSP Systems
Charlie Gonsalves
Business Development Manager, Streaming Media Group
Texas Instruments Inc.




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