Demystifying H.264

Only a few short years ago, H.264 was likened to science fiction. But fast-forward less than five years, and the gamut of content and broadband applications has accelerated the need for a way to optimize bandwidth. Multiply the service provider’s interest in finding cost-effective ways to deliver high-definition television video and reduce the cost of carrying conventional standard-definition television video, while maintaining the interest of data and voice customers, and H.264 becomes an increasingly essential component for the development of the next-generation products and solutions.

MPEG-1 enabled video on a CD-ROM. MPEG-2 became the basis for DVDs and digital TV. Now the H.264 video-coding standard has the potential to revolutionize the whole video landscape. With its robust advantages, H.264 can ease the bandwidth burden of service delivery, as well as open the service provider market to new players. For devices that range from narrowband cell phones to broadband set-top boxes to broadcast HD televisions, H.264 provides high-quality video across the bandwidth spectrum.

The bandwidth efficiency of H.264 not only provides cable operators with a means to deliver substantially higher video quality using less bandwidth but also opens the door for data and voice service providers to add video to their service offerings. For example, H.264 allows data and voice service providers, which once were limited by their networks, to use the IP-based infrastructure to deliver DVD-quality video without sacrificing bandwidth. H.264 allows service providers to take advantage of expanding IP networks and therefore deliver the level of video quality that consumers have come to expect.

Consumers enthusiastically have embraced the idea of “television on their time.” No longer limited by set-in-stone linear broadcast television schedules, the interactivity of on-demand has created a new realm of opportunities — and bandwidth challenges. The advent of H.264 enables a scalable, customized experience in which the network bandwidth, type of playback device and input from the end user are all factors in determining how a given H.264 bit stream plays back in each individual situation.

The main objective of the H.264 video-coding standard is to provide a means to achieve substantially higher video quality compared to what can be achieved using any of the existing video-coding standards. H.264 provides an average bandwidth savings of at least 50 percent versus MPEG-2.

In a typical program lineup today, many SD MPEG-2 streams likely will require a peak bit rate between 4mbps and 5mbps to avoid visible artifacts at varying times during the programs. Choosing a lower bit rate potentially may jeopardize the viewing experience. Depending on the popularity of those programs, such low video quality would impact subscriber retention negatively. With H.264, the quality concerns are rested, but perhaps at the expense of additional hardware costs.

Although very simple, the approach just outlined can lead to the erroneous assumption that H.264 delivers a consistent efficiency gain of 50 percent or more over MPEG-2. The 50 percent benchmark is only an average; H.264 is a completely new video-coding standard, not just an optimized version of MPEG-2, and therefore the actual percentage gain can vary by double-digit percentage points in either direction for different video content. The H.264 encoder implementations are still in the infancy stages. As the technology matures, it likely will see gains in efficiency just as in the MPEG-2 case.

The high H.264 coding efficiency enables video to be compressed to such low bit rates that the compressed video now can be transferred through networks using a small amount of bandwidth. This has created an opportunity for data and voice service providers to offer television services as a part of their product portfolio. For such telco-type applications, H.264 video and the accompanying audio are put into an MPEG-2 transport stream, which can be sent directly over the User Datagram Protocol (UDP). Another method involves the use of real-time transmission protocol as an intermediate layer between UDP and the MPEG-2 transport stream. Working on top of the IP layer, UDP is used to provide a connectionless transport from the source to the destination(s).

The UDP layer introduces logical communication ports, allowing multiple UDP sessions to be handled between source and destination equipment. The provider of the IP connection must ensure that the quality of the IP link is high in order to minimize or eliminate dropped packets entirely. At the network layer, routing video to the end user from the source can be done through unicast or multicast IP packets. Unicast packets are sent from the source to one destination, whereas multicast packets are sent from one source to all destinations that are part of the multicast group.

The H.264 video-coding standard allows each genre of service provider to deliver, at reasonable costs, bandwidth-intensive video applications as well as create new service tiers and expand business opportunities while satisfying a demanding consumer segment.

Consumers are now in control. They have the ability to watch their favorite programs when they want and hit the pause button when desired. And they are becoming accustomed to picture quality that few could have imagined just a few short years ago. The consumer’s appetite for personalized and on-demand access to high-quality digital SD and HD video content has grown over the past few years, fundamentally transforming the future of the video market. Thanks to H.264, cable operators, DBS providers and telecom operators, as well as other service providers, will all be vying for the same consumer.

Faouzi Kossentini is director of technology at Scientific-Atlanta, a Cisco company. He can be reached at Faouzi.Kossentini@sciatl.com.

Share this article: Email, Slashdot, Digg, Del.icio.us, Yahoo!MyWeb, Windows Live Favorites, Furl
Add this article feed to: RSS, My Yahoo, Newsgator, Bloglines