TELECOM Digest OnLine - Sorted: Re: Help Needed With WAV File

Re: Help Needed With WAV File

Robert Bonomi (bonomi@host122.r-bonomi.com)
Wed, 10 May 2006 22:37:40 -0000

In article <telecom25.174.4@telecom-digest.org>, <mike7411@gmail.com>
wrote:

> Is there any sort of program that will analyze a WAV file of modem
> sounds?

Yes.

At least 27,389 of them, in fact. *grin* No, I'm not going to list
them for you. :)

It all depends on *WHAT*YOU*WANT*TO*DO* with the file, which you
couldn't be bothered to specify.

Now, my crystal ball has been behaving somewhat erratically lately, so
what follows may not be at all relevant to what you "really" want to
do.

If you are hoping to be able to recover the 'bits' of the digital data
from a 'conversation' between two modems, this is
*virtually*impossible* for an 'standard' modem connection with an
analog-side speed above 2400 BPS. For _most_ 1200-2400 baud, it is
merely 'very difficult' -- unless it is a half-duplex
controlled-carrier communication. On the other hand, for the
'trivial' modulation systems commonly used at speeds below 500 baud,
it is fairly straihtforward to do. simple differtial analysis of the
output of a pair of properly tuned high-Q 'narrorow-bandpass' filters
(sometimes called 'notch' filters in a different application) will
extract the digital data.

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