Tips and Training >> Definitions >> H.239
What is H.239 / Dual Video / People+Content?
Simultaneous communication through multiple channels in a single communications session is the capability defined by the H.239 standard. Most users consider H.239 as a capability to split a video conference into two video connections: one for live video and the other for PC images. In practice this is the most common implementation, however, the ability to split a video conference session into two distinct video channels has some benefits and drawbacks that are generally not well understood.
Tandberg (now a Cisco organization) developed a technology that was later merged into the H.239 standard, which they called Duo Video. This, as the name implies, allowed users to send two video channels between video conferencing endpoints.
Polycom/PictureTel developed their own version of this two video channel technology, which they call "People+Content".
Today, H.239 is widely available in video conferencing systems and each manufacture's equipment implements the technology with distinct features.
Advantages of H.239
H.239 enables video conference meeting participants to both see people and to share images from another video source (typically a PC or Mac) at the same time. The result is that a group of people in location A can see and hear the people in location B while all participants in both location A and B see and interact with a presentation.
Disadvantages of H.239
Getting PC images to display well on displays at different locations simultaneously can be difficult because aspect ratios of monitors vary. For example, some displays present image in 4:3 mode and others present images in 16:9. Still others display images in 16:10 aspect ratios. These display parameters must be matched with the display capabilities of the video conferencing systems in order to produce images the way a user intends. This can be difficult.
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