changing balance of output sound

[Henkalex]

For a workshop I have to control some kind of cruise control system. The motor is controlled with the line out of a soundcard. With changing the balance of the right channel the motor is controlled.

Does someone know which function i can use for changing that balance? (I use soundcard.h) And if someone knows one, is it able to change the balance at a scale of 0 to 100?

[Ashcrow]

This is a pretty unique question. Which soundcard.h are you talking about (kernel header or a specific apps header)?