A new standard for sharing video, voice and data over a single phone line.

Overview
Video phone products and technology are not new to the marketplace. However, initial products often required the use of ISDN phone lines (digital phone lines) to carry video phone signals at data rates higher than what is available on common analog telephone lines to be used for video phone calls.

Since the introduction of 33,600 bps (bits-per-second) modems, there have been a number of first generation video phone products introduced that connect over single analog telephone lines. Unfortunately, a product from one company cannot place a video telephone call to a video phone product from another company. This lack of interoperability and the fact there has been no defined standard for video quality and connectivity has prevented consumers from buying video phones in large volumes.

The H.324 Standard
H.324 is a new standard that provides a foundation for interoperability and high quality video, voice and data based phone calls. This standard has been recently adopted by the International Telecommunications Union (ITU).

The H.324 standard specifies a common method for video, voice and data to be shared simultaneously over high speed modem connections. H.324 is the first standard to specify interoperability over a single analog line. This means that the next generation of video phone products will be able to talk to one another and provide a foundation for market growth.

How Does H.324 Work?
The H.324 standard uses a normal 33,600 bps modem connection between callers. This is the same type of modem connection that is used today to connect PC-users to the Internet and other on-line services.

Once a modem connection has been established, the H.324 standard specifies how digital video and voice compression technologies are used to convert sounds and facial expressions into a digital signal. The H.324 standard defines how these signals are compressed to fit within the data rate allowed by analog phone lines and modem connections.

The maximum data rate allowed by modems is up to 33,600 bps. The voice is compressed down to a rate of around 6,000 bps. The video picture is also compressed, and uses the rest of the bandwidth allowed by the modem connection.

What types of products will the H.324 standard?
H.324 capability will be added to new phones in a variety of shapes and sizes. The following are examples of video phone products consumers will see over the next couple of years:

There will also be PC-based video phone products available that will run on slower PC's. These products will be more expensive than software-based video phones and use add-in boards with advanced digital signal processors (DSPs) to compress audio and video and perform modem functions.

What type of quality can I expect?
Although the video quality is much better than in earlier versions of analog video phone products, it is not "TV" quality. The voice will sound like a normal phone call, but the video picture will vary depending on what screen size is used. For example, if an image is displayed inside a 176 x 132 pixel window on both ends of a video phone connection, the video picture can be delivered up to 15 frames per second. This rate is roughly half of the frame rate used for television.

The H.324 standard states that video phone products can deliver up to 15 frames per second. The actual frame rate for a video phone will vary depending on the size of the video window selected and the movement of participants during a video phone call.

Can I use any 28.8 modem for video phone calls?
Modem products require support for an industry protocol known as V.80 to interface to H.324 video phone applications. This protocol does not exist in most PC-based modems and will be available in future product releases.

Ask a modem dealer for a V.80 modem to be video phone ready.

What is Voice-Call-First?
Voice-call-first is the simplest way to connect with someone who has a video phone.

Video phones plug into the same phone jacks available in side any home. When someone wants to place a video phone call, they actually start by placing a normal phone call. Once answering a call, a user can elect to go into video phone mode. To see the other person, simply press a connect icon on your PC screen and touch the physical "connect" button on a stand-alone video phone. It's simple!

Note: Phone lines will mute for five to ten seconds while the modems connect to the current telephone call, then the video phone mode is initiated.

What are some important features of H.324 video phones?
Interoperability - Products should comply with the H.324 international standard. Voice-Call-First - Makes dialing a video phone call as simple as a normal phone call. Low Cost - PC software-based video phones will add H.324 video phone capabilities to new Intel Pentium Processor-based PCs.

H.324 Glossary