[CQ-Contest] RES: Live audio during WW Phone

Dave Pascoe davekm3t at gmail.com
Tue Oct 25 13:21:30 EDT 2005

On 10/25/05, PY5EG <py5eg at inepar.com.br> wrote:
> Hi Randy:
> Excellent . Congratulations. This is really something I would like to have.
> After contest I would like to talk with you on this regard.
> 73
> Oms PY5EG

Hi Oms-

Since this is likely to cause a number of technical questions to come
up, I thought I would head those questions off with this posting.

The system uses MP3 streaming via a network of Icecast2
(www.icecast.org) servers (running on Linux, & FreeBSD, but Icecast2
runs fine on Windows, too) that I run for my www.liveatc.net site. 
This is how the whole idea oringinated...Randy and I were sitting
around talking about the contest and I was telling him about my web
site since he mentioned his son is interested in aviation.  So he
thought it would be cool to broadcast the contest and I agreed.

The whole system is based on replicated unicast:

broadcaster -> central Icecast2-->slave servers->listeners
(k5zd)             server

The broadcasting machine uses a version of Stream Transcoder
(http://www.oddsock.org/tools/streamTranscoder/) to feed a central
server running Icecast2 (from www.icecast.org).

Listeners connect to the central Icecast2 server, which runs a custom
instance of Icecast running on a special port for load balancing.  The
listener is then redirected to one of the replicated (slave) servers. 
The slave server then "pulls" the requested stream from the central
Icecast2 server (i.e., only the requested streams are replicated).
It's proven to be a very reliable system.

But it all boils down to having access to bandwidth.  CPU/RAM are
pretty irrelevant since Icecast has a pretty small footprint and CPU
requirements.  All the encoding is done on the broadcaster end -
Icecast is just "passing the stream."

The system is limited to about 1,000 listeners, mainly to conserve
bandwidth, but it scales to thousands of simultaneous users.  And it's
standards-based so any client software capable of receiving MP3 audio
streams can tune in.  This is in stark contrast to proprietary systems
that require Real Player or Windows Media Player, for example.

Hope this helps explain the system.  It's not rocket science but it's
fairly reliable.  Many internet radio stations run using Icecast2 and
I believe it to be the best all-around system out there, and it's

Another option to investigate if you don't have access to (free,
cheap) raw bandwidth is Peercast: http://www.peercast.org/   Peercast
allows you to broadcast one stream and have it relayed between
listeners in a P2P fashion.

If this experiment is successful, I may consider opening this up to a
wider audience of "broadcasters" for CQWW CW, if anyone is interested.


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