sgsmix_set_headphone_vol
sgsmix_set_headphone_vol(sc->sc_sgsmix,
sgsmix_set_headphone_vol(sc->sc_sgsmix, 0, 0);
sgsmix_set_headphone_vol(sc->sc_sgsmix, left, right);
void sgsmix_set_headphone_vol(void *, int, int);