[Icecast] Variable bitrate and bandwidth usage

[Leo Currie]

Hi -

Suppose I have a Q-1 Vorbis stream being served from a machine on a 
low-bandwidth internet connection. I listen to the stream locally using 
Winamp, which shows the bitrate fluctuating between around 35-55 kbps, 
the average being 48k.

Now suppose I have 10 external listeners connected. How much bandwidth 
will they need/use? Common sense says:
average bitrate * 10 = 480kbps (plus any overheads)

Here's the question:
If I have 10 listeners connected, and the bitrate fluctuates up to 
55kbps, then is the actual bandwidth requirement at that instant 550kbps?
Or are the fluctuations more rapid than I can appreciate from the Winamp 
display?

Or to put it another way, over what period of time is the average 
bitrate calculated, and is this period significant in terms of average 
buffer size?

Also just quickly - could the external authentication mechanism be used 
to reject new connections when bandwidth usage reached some limit?


Thanks

Leo