High Definition Video Conferencing:

The Big Picture

Introduction:

Recently, high definition video conferencing equipment has been manufactured, demonstrated, and marketed by a growing group of vendors and is widely purported to be the next big step in the evolution of video conferencing technology. Since the first LifeSize high definition systems shipped in December of 2005, organizations have beengradually adopting the technology and a lot of interest has developed in the video conferencing community regarding the new high definition products from a range of vendors. In the midst of all of this activity, the video conferencing end user – particularly in the educational environment – is often left asking a lot of questions. What exactly is high definition video conferencing? How does it compare with the video quality of other systems currently being used? What resources are required to support high definition video conferencing? What direction is the industry headed in, and what further developments can we expect in the future? The purpose of this document is to answer these questions and educate users, support teams, and decision-makers about the end-to-end requirements and possible applications of high definition video conferencing technology. Additionally, many people will probably read this information and realize that high definition video conferencing is not something they need for the foreseeable future, but will have an interest in learning more about video standards and the different kinds of video conferencing formats that are available.

Background:

In the past, you may have read about various video formats, observed the statistics of video endpoints during calls, and seen terms such as CIF, SIF, 2SIF, QCIF, QSIF, 4CIF, and 4SIF. You may have also wondered why there are so many possible formats. The Common Intermediate Format (CIF) standard provides 352x288 pixels, or picture elements, of video resolution. You may have also seen a standard called Source Interchange Format (SIF), and this method of displaying video provides 352x240 pixels of video resolution. CIF and SIF are the most commonly used video formats in K-20 video conferences today. For those who are interested, the CIF video format is actually specified in the H.261 and H.263 video protocols, and began as an attempt to come up with a compromise between the NTSC (US) and PAL (European) video formats. SIF, on the other hand, is mentioned in Annex D of the MPEG-1video standard, and more closely matches the image format (aspect ratio) of the NTSC video standard commonly used in a number of countries, including the United States.

On some legacy systems, or while participating in MCU calls including endpoints that are legacy systems, you may notice the QCIF or QSIF format in use. QCIF, or Quarter CIF has a resolution of 176x144 pixels and QSIF has a resolution of 176x120 pixels, resulting in ¼ of the image resolution of CIF and SIF. These formats are generally used by video conferencing systems with very limited processing capability and/or over very low-bandwidth connections.

Going the other direction on the scale, 4CIF has a resolution of 704x576 pixels and 4SIF has a resolution of 704x480 pixels, providing much better picture quality than CIF and SIF on equipment that supports thesehigher-quality formats. 4CIF and 4SIF can be thought of as improved definition video conferencing, but not yet high definition. These improved definition formats require call data rates between 256 Kbps and 1 Megabit per second (Mbps). Also, even many modern video conferencing systems have very limited support for 4CIF/4SIF. For example, the Polycom VSX product line only supports 4CIF at a maximum of 7.5 frames per second (fps) when the codec is set to sharpness mode for a specific camera, so this feature would probably only be used for a device such as a document camera that supports 4CIF and doesn’t require the higher frame rates that make live video look more natural and lifelike. The VSX doesn’t have the digital signal processing resources to run 4CIF at the standard 30fps used for live video.

High Definition Defined:

True High Definition video conferencing typically consists of a video resolution of at least 1280x720 pixels at 30 fps at a call data rate of at least 1 Mbps and as high as 4 Mbps. You will generally see a ‘p’ after the 720, and that means the horizontal lines comprising the picture frame are drawn on the screen in sequence (progressively) rather than in an interleaved fashion as with some other(particularly NTSC-based) video formats. Video conferencing systems are now available that support the 1080p video format and they tend to be more expensive because they require increased digital signal processing to support the higher resolution. The image below shows a graphical comparison of five of the video conferencing formats in use today along with examples of screen resolutions for some commonly used devices:

One additional development to be aware of is the H.264 High Profile implementation announced some time ago by Polycom. Polycom claims this technology enables HD quality at call speeds as low as 512Kbps. Opinions are varied regarding how well this actually works and High Profile tends to require specific equipment on specific software versions on both ends of the conference in order to be fully supported. You will have to evaluate its merits and limitations based on your own experience and customer requirements. There is a link to a Polycom brief on H.264 High Profile at the end of this document.

You may have noticed HD monitors have a wider image than the traditional TV monitor, and thepicture is shaped more like a movie theater screen. This difference has to do with the aspect ratio of various video formats. For decades, the main television format used in this country was NTSC, with an aspect ratio of 4:3 as shown below:

Modern HD monitors and movie theater screens use a 16:9 aspect ratio, creating a differentformat than the 4:3 approach.These aspects ratios are compared in the following graphic:

One final comment about display resolutions and aspect ratios: You may have done the math for the 720x480 DV NTSC resolution shown above and realized that content at this resolution does not calculate to 4:3, although it is often displayed on 4:3 screens. The best way to explain this is to tell you that the pixels in different display formats are not always square and leave it at that. Generally, you will not have to worry about this detail in the video conferencing or computer realms, but it is good to be aware that some in some formats the pixels are square, while in others they are rectangular.

Resources Needed to Support High Definition:

One challenge of high definition (HD) video conferencing is the need to provide an end-to-end solution in order to effectively support and use the technology. There are a number of components that you will need to have in place and correctly configured in order to support HD video conferencing as follows:

  • HD-capable camera
  • HD-capable video device (codec)
  • Plenty of high-quality bandwidth
  • Interfaces and cables that support HD
  • Monitors and/or projectors that support HD (resolution, aspect ratio, size)
  • Components that support all of the above at the remote site(s)
  • In a multi-point call, all of the above plus an MCU that supports HD and is configured/enabled as required

Additionally, there are a few other considerations as follows:

  • The codec will need to be backward compatible so that it works with all the legacy video equipment, call speeds,and protocols out there!
  • Once users become accustomed to HD, better audio components and stereo capability may be needed to bring the audio up to the same standards as the video.
  • Although not true HD, improved definition technologies such as 4CIF and 4SIF may require upgraded equipment in order for you to take full advantage of their capabilities.
  • Even non-HD video formats often looks better on a modern, high resolution monitor, because the anti-aliasing/up-sampling process used in newer monitors increases the perceived image quality.

As with other types of video conferencing equipment, users are encouraged to evaluate high definition video conferencing systems before they buy to ensure that the equipment will work properly with their peripheral equipment, network infrastructure, and other K-20 video conferencing systems. This is particularly true with HD equipment, because it is so new to the market and the hardware and software are not as thoroughly tested in live environments as systems that have been on the market for a longer period of time. K-20 MCU resources have recently been expanded to include HD video conferencing support based upon end-user needs.While testing is ongoing, institutions may opt to have video conferences requiring HD support placed on the new Tandberg/Cisco MSE8000 MCUs by contacting the MCU support staff at 888-934-5552. Keep in mind you are also able to conduct true high definition calls either in point-to-point mode or using embedded MCU features (if so optioned) on any HD endpoints you acquire as long as the remote site(s) also have HD capable devices that are configured correctly and available bandwidth exists to support the HD call from end-to-end. Lastly, remember that you can expect to pay a higher price for HD equipment because of the more advanced codec,camera,and peripheraldevices needed to support the technology.

The Future:

As mentioned earlier, various vendors can be expected to introduce a variety of HD endpoint equipment with higher resolutions and other features at lower cost in the future. Also, modern MCU products from a variety of vendors will support more advanced features such as mixed HD and non-HDendpoints in calls, continuous presence support in HD mode, and probably additional capabilities as well.

Additionally, some developers are already experimenting with far higher resolution video formats as well as optical media capable of Terabyte storage densities and displays that create 3D effects in an attempt to introduce a greater sense of realism into the HD experience. There are several items to remain mindful of related to these developments:

  • Even with today’s advanced algorithms and encoding/decoding techniques, increases in definition require considerably more bandwidth to supporthigh-quality calls.
  • Higher resolutions and greater realism are expensive features that may or may not be worth the cost in a specific video conferencing environment.
  • With the monitor sizes utilized by many personal computer users and smaller video conferencing room installations, the perceived quality improvement of HD video isn’t as noticeable as it is on a larger(greater than or equal to 32”) monitor with a wide, 16:9 aspect ratio.
  • Monitor technology can be expected to produce improved quality and increased feature sets at decreasing cost in the future.

Supplemental Links:

A Paper on Tandberg's Native Resolution Technology - This document contains some interesting information about video formats as well as a description of Tandberg’s Native Resolution feature.

Polycom PDF about HD Video and Optimal Viewing Distances - This article addresses the topic of optimal viewing distance for different screen sizes and resolutions within a larger discussion about the evolution of HD video conferencing.

A Polycom Application Brief about H.264 High Profile - This document provides some information about Polycom’s H.264 High Profiletechnology.

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NTSC Video Working Group 12/11/2012