Hello,
After hours searching in the forum, I can't find anything usefull for this. What I have to do is find a command line application that takes mp3 mono files and converts them into stereo mp3 composed of the mono mp3 in one of the channels, and all silence in the other (the channel where the mono file goes should be chooseable).

I can do all this process through AUDACITY, but I am trying to find a command line program.

Thanks.

...i'm assuming there is some sort of playback limitation?

why would you do that?

The thing is I have to thow two different audio streams at the same time through only one stereo output. The soundcard is on a systems that goes into a bus. No hardware modification can be done, and I need to reproduce a voip call with de driver, and at the same time some audio messages to the passengers. Obviously both are independent.

I don't know of such a tool, but you might want to take a look at the thread I started about Convolver here: http://www.hydrogenaudio.org/forums/index....showtopic=41944

It is an example of how to swap stereo channels in a stereo WAVE file.
The filter for your case would be like this:
(save as mono2stereo.txt)
where C:\_\MonoIR.wav is a Dirac impulse file created by generate_dirac_delta.exe as explained in forementioned thread.
More details about filter (painful) syntax here.

This was for the one-time setup.
To apply the IR filter to your file, use C:\Program Files\Convolver\convolverCMD.exe

e.g.
"C:\Program Files\Convolver\convolverCMD.exe" 0 0 mono2stereo.txt input.wav output-stereoleft.wav

If you want the mono channel to be mapped on the right channel:

and
"C:\Program Files\Convolver\convolverCMD.exe" 0 0 mono2stereoR.txt input.wav output-stereoright.wav

Granted, convolverCMD crashes at exit and leaves wisdom.fftw everywhere, but it does the job, until you find something better.
Hope this helped.

Rasqual