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What is Resolution?

One of the least understood and most vexing areas of video communications relates to what is often referred to generally as "resolution". Resolution is generally accepted to imply the clarity with which one sees a video image that is presented electronically. In the realm of video communications, there are many factors that affect this and these factors interplay in such a way as to make improving video resolution or clarity a challenge.

There are three key areas to consider when tuning a video conference image:

A. Resolution Pixel, Spatial, Temporal
B. Aspect Ratio
C. Motion handling

Resolution Pixel, Spatial, Temporal

Video conferencing systems can be configured to output varying Pixel Resolutions and this must be matched to the presentation setting on the monitor being used such as 1024x768. In addition to this pixel resolution, the ability of a monitor to uniquely address each pixel (Spatial Resolution) will affect the clarity of the images presented. Spatial resolution can be vastly different between monitors and this is something that can dramatically affect image clarity. In addition to Pixel and Spatial resolution, Temporal resolution which is affected by the frame refresh rate of the codec can affect the clarity of moving images.

Aspect Ratio

Video conference images can appear either stretched or squashed depending on the aspect ratios of the video conferencing codec and the display to which it's connected. Aspect ratios of 16:9 are common for High Definition system and this selection should be made in the monitor setting. For Standard Definition video conferencing systems images are best displayed in a 4:3 aspect ratio.

Motion Handling

Compression techniques for video communications include H.261, H.263 and H.264 among others. Generally H.264 is considered to be the most efficient compression technique of these and therefore video images are likely to show a greater level of clarity when transmitted and decoded using the H.264 algorithm.

Fixed and unchanging images such as those presented by a document camera may not require H.264 and these images may appear equally clear using other algorithms. Moving images, however, greatly benefit from the use of an efficient algorithm and the real time clarity of moving images is widely preferred using the H.264 codec.

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