There are HDMI over ethernet extenders for sale.
They transport the HDMI signal over two CAT5/6 cables max. 100 metres and back to HDMI.
That makes those CAT cables dedicated to that propriety extender/converter system, and
not integratable into network, like the guy asked.
... sort of an IP based monitor.
I looked for the same thing in 2010, and the only relyable system was, like mentioned above, attaching a computer to each screen.
Solutions are Rpi, NUC, Thinclients, MediaplayerPC, VesaBoxPc...
I had some bad expierience with streaming also, the reasons were problems with subtitles, unrecognised sub-MKV and VOB formats... and internet tells me I'm not alone. The new "solution" to a previously unexisting problem was called "server transscripting" but I lost a complete day there with... new problems and exceptions.
So my new requirement was: A system that plays video + has
real network access.
To not loose too much time again, I disregarded DLNA and XBMC etc, and went for a normal PC with normal Windows and normal VLC.
I'm sure those cisco guys will choose another solution here.
Now, 5 years later, I would maybe choose Rpi or NUC instead of a uATX.
I understand the difference between our situations, if you have much screens etc.
Maybe run Linux with a self starting script on it?
Can you give a very tight description of the video formats you want to stream?
Or do you want to show also PDF's or presentations?
Does every screen display the same thing at the same time?
Do you want to allow user control at the position a such monitor or is everything organised strictly centralised?
A thing to think about also is the number of sceens, and the expected bandwidth.
Many Pc's wanting to get videos over the network will give much more load than those PC's subscribing to a broadcast stream.