Hi Konstantin,
This is probably not the best list for your questions, as this list is
concerned with Icecast development, but I'll try to help.
> if I'm planning to open a web-site that has a built-in player with
radio
> streaming server, what's the requirements for the hosting (besides
> unlimited traffic)?
Few streaming hosts are genuinely unlimited, as you may find once you
start using really large amounts of data :-)
> If there can be about 50000 users minimum, must it
> be VPS hosting, if the streaming hosting itself is reliable and allows
> this number of users?
At this scale, assuming you mean 50,000 concurrent users minimum rather
than 50,000 connections per month, you would probably not be serving all
the streams from a single virtual private server. More likely you would
have some sort of content delivery network (CDN) made of multiple
servers in different locations.
> Does it depend on the streaming server?
It's more dependent on the streaming technology and the bitrate. Icecast
is unicast, so each stream listener added scales up the bandwidth
requirement in a linear fashion. Assuming you are streaming across the
public Internet, you will need to do some serious planning to serve
50,000 concurrent users well, regardless of the server you use.
Cheers!
Daniel