How to write a LineIn Audio Play-Through Utility

How to write a LineIn Audio Play-Through Utility

Post by V00gRGV2ZW » Fri, 31 Oct 2008 10:37:01


How do I write LineIn Audio Play-Through Utility? To clarify I want
automatically play an audio signal feed in on line-in port. The input will
come from a device that generates tones. The program will be started and run
in background. Any sounds generated by device will play on PC with no
intervention required by me. Any examples? I would like to use C# preferably
but will also use C++.

There is a catch, my notebook does not have LineIn so I was hoping to use
Microphone input.

Thanks!
 
 
 

How to write a LineIn Audio Play-Through Utility

Post by Chris P » Fri, 31 Oct 2008 22:25:31


To get line-in/mic-in to play through the speakers all you have to do is
set the playback mixer to unmute that input. On XP run "sndvol32". On
Vista the mixer may or may not allow it depending on the soundcard in which
case you would have to write an app to capture the input and echo it back
out. To connect a line level signal to a mic input you will need a special
cable that has resistors in series in order to drop the voltage level from
1V p-p to 50-100mV p-p. The signal will also become mono.

--
http://www.yqcomputer.com/
[MS MVP for DirectShow / MediaFoundation]

 
 
 

How to write a LineIn Audio Play-Through Utility

Post by V00gRGV2ZW » Fri, 31 Oct 2008 22:56:08

have values to use for resistors?
 
 
 

How to write a LineIn Audio Play-Through Utility

Post by Chris P » Sat, 01 Nov 2008 01:50:07


It will depend somewhat on the level out you are getting from your
tone-generator. Fortunately you have some control over the input level
that you can adjust within a certain range. I would guess that a value of
between 50K and 100K Ohm should do the trick.

On the mic input connector wire only to the tip and the shield. The ring
contact is a 5V supply line for powering microphones.

--
http://www.yqcomputer.com/
[MS MVP for DirectShow / MediaFoundation]
 
 
 

How to write a LineIn Audio Play-Through Utility

Post by V00gRGV2ZW » Tue, 04 Nov 2008 02:55:01


Could I use a potentiometer? I would use the centertap and one of the end
points. and I guess a 100K ohm would be adjustable from 50K ohm to 100k ohm?
I would use a mini pc board type pots with very low wattage --
http://www.yqcomputer.com/

Thanks,