Sound Card <-> Sound Card Via Data 
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 Sound Card <-> Sound Card Via Data

G'Day All....

After a late night a couple of us started talking about sound cards. In
particular taking  audio from the input of the card and passing it via a
serial port or network connection to another sound card on another
machine. I have seen a commercial product which does this however the
data comes and goes half duplex. (only one way at a time).

Some of the questions I have are:

Can the sound card be full duplex?

Can it be turned into a data stream for real time 2-way audio communication?

Could this be handled by Vbasic (with the external modules if necessary)?

If I stay up late looking at the possibility doing voice over a LAN when
I have a perfectly good phone on my desk should I "Get a life"

Best Regards & Thanks for any input.

Peter VERNON

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Sun, 19 Oct 1997 03:00:00 GMT  
 Sound Card <-> Sound Card Via Data

Quote:

> G'Day All....
> Some of the questions I have are:
> Can the sound card be full duplex?
> Can it be turned into a data stream for real time 2-way audio communication?
> Could this be handled by Vbasic (with the external modules if necessary)?
> If I stay up late looking at the possibility doing voice over a LAN when
> I have a perfectly good phone on my desk should I "Get a life"

Peter,
Try this link:
http://www.cs.ta-berlin.del/~jutta/toast.html
It has source code in C for real time voice data compression,
something like 64kps(4hz(voice BW) X 2(mim Sampling rate) X 8(8level
PCM) to less then 10kps.  It has dos versions of the algorithm.

They have other links to related projects:
Global phone
RealAudio - real time audio files over the net
and some others That I can't remember.
I pretty sure that this has already been done, so you should be able
to find something specific about it.

I think the jest of it would be capturing the *wav files generated
when recording(on the fly), compressing this into fixed length small
cells(when recording starts grab the wav info every N seconds) then
send over the LAN with a file transfer protocol.  At the other end rebuild the
compressed(not sure exactly how the compression algorithim works)
cells and send these as wav files to the sound card to play.  For this
to work you would have to manually "record" via a command button(or
keystroke).   There would probably be lots of delay and such, in order
for it to be a really robust(finally worked that word into a
conversation) system you would want to be able to detect silence, and
act accordingly, ie not sample and waste time compressing sampled silence.
Goodluck!
P.S. if you do any work on it, let me(us) know how it goes.
----------------------------------------------------------------------
Greg Carter
Fourth Year Electrical Engineering
Carleton University
Ottawa, Ontario, Canada


Take a look at my home page on the
World Wide Web: http://chat.carleton.ca/~gcarter
----------------------------------------------------------------------



Mon, 20 Oct 1997 03:00:00 GMT  
 
 [ 2 post ] 

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