H.264 SVC – Seeing might be believing

ITU develops a new videoconferencing standard

Perhaps the biggest limiting factor keeping organizations from widespread deployment of high-definition videoconferencing is the need for high-bandwidth coupled with low latency across the WAN. Nemertes research participants consistently cite the need to add bandwidth, WAN optimization, or even deploy dedicated overlay networks to support high-definition video and telepresence systems.

For virtual workers, the lack of guaranteed low-latency bandwidth is particularly acute as teleworkers, mobile workers, and field forces often rely on public network services, such as residential Internet connections or mobile-data offerings. Even on cable/DSL services, where bandwidth is plentiful, there's no guarantee of low-latency or low packet loss, meaning videoconferencing, especially high- definition, is often unusable.

To address the need to deliver high-quality video over variably performing data-network services, the International Telecommunications Union (ITU) has developed a new videoconferencing standard, H.264 SVC (Scalable Video Coding). H.264 SVC is based on the idea of slicing individual frames into multiple layers, with each layer holding part of a single frame's image (and audio). Layers are transmitted between end points, which combine the layers as part of the decoding process to deliver video and audio to the conference participant(s).

By splitting frames into multiple layers, the loss of a single layer, or even a small percentage of layers, doesn't noticeably affect perceived video quality. End-points simply reconstruct frames based on whatever layers they receive. H.264 SVC sessions still provide high quality, even if end points are only able to exchange a small percentage of layered frames.

Demonstrations from vendors offering H.264 SVC solutions show noticeable change in video quality, even in networks with 10% or 20% packet loss. The current widely adopted standard for HD, H.264 AVC (Advanced Video Coding) lacks this layering ability, meaning that lost packets result in the loss of an entire frame, leading to choppy or unusable video.

Given its ability to provide high-quality video across unpredictable networks, I expect H.264 SVC to emerge as a key video technology for mobile devices and surveillance. Already, General Electric has introduced H.264 SVC-based video codecs for surveillance systems.

H.264 SVC also could pose a threat to Microsoft's proprietary RTvideo codec, currently promoted on its ability to support high-quality video across variably performing networks.

But with any technology advancement, there is small print. We're early in the H.264 SVC game. Only a handful of vendors have announced support for H.264 SVC and in most cases, their implementations aren't interoperable. The ITU only has standardized one part of the H.264 SVC process, the encoding and decoding of frames. Standards for frame transmission between end points and translation between H.264 SVC and AVC are still under development. Videoconferencing vendors, including Radvision and Vidyo (and their partners), already have introduced H.264 SVC solutions, but until final standards are established, interoperability among different H.264 SVC solutions isn't realistic.

One key area to resolve is interoperability between systems using H.264 SVC and H.264 AVC. Here again, vendor approaches will vary until the ITU defines the standards. Common approaches involve a gateway between SVC and AVC end points, or the use of a single MCU, able to translate between SVC and AVC. Either approach has drawbacks, such as introduction of additional complexity or latency. But they are necessary evils, as few organizations will find justification for a forklift migration to an all-SVC architecture and instead must support a mix of endpoints in the near term.

So what should videoconferencing managers do now? Here are a few steps:

1. Come up to speed on H.264 SVC. Learn about your vendor's plans for the technology, and understand its interoperability and migration strategies. Keep in mind that although options today are few, that may not be the case in six months or a year.

2. Evaluate H.264 SVC offerings on the market today, especially for mobile workers or teleworkers relying on unmanaged, public or residential Internet connectivity for access to your corporate network.

3. Look for backwards compatible options for H.264 AVC equipment that you are deploying today. Evaluate your vendors on their ability to get you to H.264 SVC down the road.

4. Address interoperability concerns early in the evaluation process.

5. Look to H.264 SVC solutions for non-videoconferencing video applications, such as video surveillance over low-speed or variably performing network services (such as cellular data).

Copyright © 2009 IDG Communications, Inc.

The 10 most powerful companies in enterprise networking 2022