Guessing stream codec?

I am trying to automate the maintenance of a directory of Internet
Radio streams.  I want to get stream bitrate and codec type
automatically.  Most stations don't put this info in the HTTP header.

I can guess bitrate by streaming a big chunk of data (a meg or more?),
timing it, and dividing bits by seconds.  If the stream is a true
radio station and not a file (aka podcast), this guess should be close
to the actual bitrate, modulo some startup burstiness.  Unfortunately
I'm not yet sure how to tell a true radio station apart from a
podcast.

The thousand or so stations in my directory all return Content-Type
fields that are in this list:

  text/plain                      audio/x-mpegurl
  text/html; charset=ISO-8859-1   audio/x-ms-wax
  text/html                       audio/x-scpls
  text/html; charset=utf-8        audio/x-scpls pls
  text/plain; charset=iso-8859-1  video/x-ms-asf
  text/plain; charset=ISO-8859-1  video/x-ms-asx
  text/plain; charset=UTF-8       video/x-ms-wmx
  application/octet-stream        video/x-ms-wvx
  application/x-mplayer2

This doesn't give me the details about the codec that I want (is it
mp3?  flac?  wma?  encrypted?).  So I think I need to get a chunk of
data and feed it into some sort of decoder to guess the codec.  Can
anyone suggest such a decoder/guesser that runs (or can be ported to)
linux?

Thanks,
Dave