IPTV media stream server suggestions?

[muz_j]

I'm curious if anyone who's more familiar in this space has any suggestions for an IPTV media streaming server - either software based, or perhaps an appliance (rack mounted) ?

I'm looking for something to host media files, that can stream those to approx 50 - 100 IP TV's via Ethernet (LG Smart TV's in this instance).
Initially I was thinking something like Plex, but that's functionally limited if internet access is not available.
I'd like something that works without needing the server or client devices to externally authenticate with an online server.

I've got a several ideas, but figured I'd see if anyone has a suggestion I should consider.
I'm open to open source or proprietary licensing and if it's something software based, it would need to run on a Windows or Linux server - and if it's Linux it needs to be a well supported distribution.

Appliance wise I've been looking at Edgeware orbit and Cisco solutions, but both of those are pretty expensive and I'm thinking something simpler is more appropriate given the size/scale of the environment.
Edgeware's Orbit appliance is shown here: http://www.techex.co.uk/edgeware/orbit-2x

Content wise, it would need to support as many common video formats as possible and handle at least 50 1080P streams as a minimum.

...I'm open to ideas, but bear in mind this is enterprise orientated.
Thanks