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[This post is taking part in our Designing Hardware for HD series. Be sure to check it out!]

Mazal Tov! You have decided to develop an HD Videophone. You want it simple, easy to use and working properly. But do you know how many video streams you will need to handle?

One In, One Out

In its most simple form, a videophone requires only two video windows: one for the camera you connect into the system and another one for the output to the display, which is from the video coming off the remote videophone.

This kind of design will be limited to a small set of products. Mainly a desktop videophone, where there are no additional video requirements.

One In, One Out

In most cases – it is not what you need.

The Additional Stream

Sometimes, there will be a need for an additional video stream for the device you are planning. This additional stream doesn’t take part in the call itself, but is required as part of the end product.

Need an example? Think of a videophone hardware that is targeted at consumers. You connect it to your set-top-box and your television and it essentially allows you to watch television while on a conference call, doing both activities at the same time and splitting the screen to accommodate both streams on the same layout.

The Additional Stream

You can think of it as a videophone that doubles as a video multiplexer. We’ve had several requests in that direction by customers.

Data Sharing

In data sharing, there is a need to get the stream from the additional stream (a secondary video source) and encode it as part of the device itself. Usually this is done for data sharing purposes, where you want a PC to be connected to the device and its display shared with the remote end of the call.

Here, there’s a need for a secondary video input that can be encoded, and usually for running two decoders at the same time (to be able to decode primary and secondary video from a remote videophone). This added complexity needs to be taken into account when designing the hardware, as raw video data and encoded video data need to be passed between chips in the system.

Data Sharing

This is a common design requirement for enterprise video conferencing solutions.

Dual Screen

Data sharing can be further enhanced: if we can deal with dual inputs, why not dual outputs? Have two monitors, each displaying different kinds of content?

Dual Screen

This kind of a solution fits well in video conferencing room systems, where a presentation is usually part of a conference call. It is also quite common these days, so if you’re designing for a large display in an enterprise setting, you should be thinking of having dual video outputs.

Anything Else?

This is most definitely not an exhaustive list of the options (TelePresence systems, for example, might require a lot more video inputs and outputs), but it should fit the majority of videophones and also serve as a baseline to think about what exactly your needs are. It will also greatly affect how your hardware design should look like, but it is not the only aspect. For my next post in this series I’ll try to cover the issue of layouts – what exactly is shown on the display(s).