ClearOne Digital Media - Manual (Page 29)

Because HDMI and the EDID specification were not originally conceived to be used for
multi-point installations or applications, problems may be introduced in systems typical
of what AV professionals design, install or maintain, where display devices will not show
content. Since HDMI switches are required for large multi-source and multi-display systems,
and these same switches are responsible for collecting the display’s EDID and providing
a unified version to the source, it must be noted neither the HDMI nor EDID specifications
suggest how to do this task reliably. Which is why different HDMI switches and repeaters
often behave in unpredictable ways as each manufacturer implements the standards
differently.
As illustration, consider the following system.
Your client wishes to connect a 1080p projector with a surround sound processor in the
media room or home theater, and a 720p / 1080i display in the master bedroom using the
internal speakers for audio. So the question is how should the HDMI switch combine the
EDID information so each display shows the optimum image, or in some cases shows any
image at all, and audio is correctly passed to each environment?
It is our experience that certain devices on the market solve this problem by simply copying
the EDID from the first output. However in our scenario this would mean1080p video and
surround sound audio is sent to the family room which neither supports1080p or surround
sound audio.
Another approach some HDMI switches take is to create a merged EDID that limits the
content to only what both rooms can support. Unfortunately this means our media room /
home theater is now artificially limited to 720p video and stereo audio. Once we expand this
scenario to multi-point installations with multiple rooms, source devices and displays it is
easy to see why HDMI in many systems is problematic and why many AV professionals have
“defaulted” back to analog interconnection schemes. After all with analog you are ensured
to have picture and sound on every screen in every room. Of course never mind the quality
our customers paid for is never fully realized. At least it is nearly guaranteed to work every
time or so is the rationalization of this approach. However with ClearOne’s StreamNet digital
media solution there is now a way to not only provide your customers the very best picture
and sound, and do so reliably.
pg 29 StreamNet Digital Media and System Design Reference Guide
Digital File Security and DRM