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High-definition video conferencing vs. bandwidth capacity

Video service quality can make or break a collaboration session. But high-definition video conferencing, in particular, requires a robust network and plenty of bandwidth.

As high-definition and 4K televisions become pervasive in the consumer world, more employees are expecting high-quality...

video at work. Delivering an equivalent high-definition video conferencing experience means understanding and addressing network bandwidth needs.

Video conferencing quality can make or break a deployment. If users have a negative first experience with a video conferencing system, they will not want to use it again, and the return on investment will be lost.

The underlying network infrastructure is critical to video conferencing quality. In general, the higher-definition video you want to provision, the more network bandwidth you'll need to buy.

Before you tackle HD video conferencing and invest in equipment, services or network upgrades, make sure you understand your video conferencing requirements. For instance, choose the right system for your company, select the appropriate video-signaling infrastructure and position your multipoint control unit (MCU) where it will scale cost-effectively.

Additionally, consider cloud-based virtual meeting rooms to offload internal MCU needs, reduce WAN bandwidth demand and support conferences with external participants. Fiscal constraints might limit your options, so you must harmonize your priorities with your budget to find the right service for your situation.

Understanding video conferencing quality

With video conferencing quality, the first major decision is to define the video quality your users need. Two key factors affect video image quality: resolution, meaning the number of bits in the image, and frame rate, the number of image refreshes per second.

Boosting either the resolution or frame rate increases the network traffic burden. Although video compression algorithms do a good job of reducing bandwidth consumption, they can only do so much.

For example, an HD 720p image that refreshes at 30 frames per second creates about 664 Mbps of data -- 1280 x 720 image size x 24 bits of color and intensity information x 30 frames per second. This 664 Mbps is typically compressed down to between 2 Mbps and 4 Mbps for transport over the network.

The table below shows typical bandwidth requirements for the resolutions and frame rates shown, using an H.264 AVC codec. Note: The emerging H.265 encoding standard reduces these bandwidth requirements by about 40%, while 4K video can eat up 1 Gbps or more.

Transport bandwidth required

Resolution

Frame rate

128 Kbps

CIF

15 fps

384 Kbps

CIF

30 fps

512 Kbps

4CIF

15 fps+

768 Kbps

4CIF

30 fps

1 Mbps

HD720

15 fps+

2 Mbps

HD720

30 fps

3 Mbps

HD720

60 fps

4 to 6 Mbps

HD1080

30 fps

6 to 7 Mbps

HD1080

60 fps

Resolution and bandwidth requirements

How much resolution do you need for adequate video conferencing quality? A good way to think about resolution is pixels per face. A primary benefit of HD video conferencing is you can see other participants' body language -- particularly their facial expressions -- so you need sufficient resolution to see facial detail.

Today, thanks to HDTV in the home, workers will not tolerate anything less in the office. The resolution required for a room-based environment with four or more people in one camera image is much higher than a personal video conference with only one person in the image. Personal video conferencing often includes a head-and-shoulders image of one person, with the face consuming 20% or more of the image real estate. In this case, CIF resolution -- 352 x 288 pixels -- would deliver about 20,000 pixels per face.

In contrast, a room-based system with four participants is likely to display a much broader view of a conference room, and an individual face may only cover 2% of the screen. In this situation, an HD 720p image will deliver about 18,000 pixels per face. Although the pixels per face are roughly equivalent to the personal video conference, the room-based system needs to deliver 2 Mbps to 4 Mbps of bandwidth, whereas the personal system only needs to deliver 512 Kbps to achieve the same result.

Frame rate and bandwidth requirements

Frame rate determines how often the image will be updated and, thus, affects video conferencing quality in terms of how well the system displays motion. You can configure video systems to use a higher-pixel resolution by dropping the frame rate. Although this tradeoff can work well for static images, it degrades the quality for dynamic images of people moving and talking.

Slow frame rates deliver jerky video images that detract from the conference experience. So, if bandwidth is limited, it makes sense to ensure a full 30 fps, even at the expense of some resolution.

Video resolution settings should also take into account content sharing. On a PC desktop, most systems will share resolution equivalent to the screen resolution of the PC. But in a video conference room, resolution may need to display a range of detail. For example, less resolution is needed for PowerPoint presentations with big font sizes than for detailed architectural or engineering diagrams or spreadsheets.

Much of this article assumes video is being used to connect participants in a conference. If HD video conferencing is being used for clear images of small details, resolution and motion support must be sufficient to make the application work well. It's a good idea to try the application in its intended environment to ensure the resolution and motion handling will deliver the needed results before you buy a high-definition video conferencing system.

Next Steps

Does your organization need high-definition audio conferencing?

How to assess video conferencing equipment

Discover the benefits of HD video conferencing

How to calculate video conferencing bandwidth requirements

Dig Deeper on Business Video Conferencing and Telepresence Technology

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