Looking for Information About Streaming Audio Formats

[Andor Demarteau]

On Fri, 7 Jan 2005, Martin McCormick wrote:

 > 	Has anyone run across any information that describes how
 > the protocols used by common streaming audio services work?
no in a snce, although msot of it should be available somehwere.
However, I suspect that specs for RTP and RSTp probably are available in
rfs.

There are ofcourse  2 parts, the network-connection used (which protocol)
and ofcourse the audio-format used.

 > 	I think one might be able to figure out some of what happens
 > by placing a Linux system running snort in full capture mode on an
 > Ethernet switch port with a Windows box as it makes a connection to a
 > radio station's web site or something similar.
sniffit may work even better or tcpdump maybe.
But that's protocl-stuff not data-analyses directly.

 > 	Has anyone run across any discussion of the nuts and bolts of
 > how these streams are decoded?
no, but sofar I know mplayer does a fine job of doing so.
If you really want to get into the details, read their source-code.
Alsthough some stuff is binary.

 > 	There are actually two issues that must be resolved; One is
 > how the data communications are set up with the remote server to start
 > the stream and, of course, how to turn that stream in to audio after
 > it is being received.  The snort capture would probably tell you
 > enough about the communications protocol to figure out how it works,
 > but the data decoding part of the puzzle is probably the hardest.
well yes. HOwever, most network protocols are listed in rfcs so are
available.
As most will use eitehr tcp or udp that's not interesting.
You'd have to look at the application-layer which sometiems simply uses
http.

Decoding the audio is somewhat more ticky and amy even be very hard if you
don't know how it was encoded in the first place.
This hwoever is either realaudio, windows-media foramt or mp3 in my
experience.

 > 	Any ideas are appreciated.
look at http://www.mplayerhq.hu and simply use that program.
Why try to figure it out if there's probably software around doing that
already for you.

 > Martin McCormick WB5AGZ  Stillwater, OK
 > OSU Information Technology Division Network Operations Group
 >
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 > Blinux-list at redhat.com
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 >

-- 
Andor Demarteau                 E-mail: andor at nl.linux.org
student computer science        www: http://www.nl.linux.org/~andor
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chairman Stichting Studiereizen Storm 2002-2004
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