private void updateDt() {
        long tmp = System.currentTimeMillis();
        if(firstrun) firstrun = false;
        else {
            dt = ((float)(tmp - prevTime)) / 1000.0f;
            if(dt == 0.0f) dt = 0.01f;
            sampleFreq = 1.0f / dt;
        }

        prevTime = tmp;
    }