src/main/java/net/sourceforge/jaad/aac/sbr/HFGeneration.java
private static void calc_prediction_coef(SBR sbr, float[][][] Xlow,
		float[][] alpha_0, float[][] alpha_1, int k) {
		float tmp;
		acorr_coef ac = new acorr_coef();

		auto_correlation(sbr, ac, Xlow, k, sbr.numTimeSlotsRate+6);

		if(ac.det==0) {
			alpha_1[k][0] = 0;
			alpha_1[k][1] = 0;
		}
		else {
			tmp = 1.0f/ac.det;
			alpha_1[k][0] = ((ac.r01[0]*ac.r12[0])-(ac.r01[1]*ac.r12[1])-(ac.r02[0]*ac.r11[0]))*tmp;
			alpha_1[k][1] = ((ac.r01[1]*ac.r12[0])+(ac.r01[0]*ac.r12[1])-(ac.r02[1]*ac.r11[0]))*tmp;
		}

		if(ac.r11[0]==0) {
			alpha_0[k][0] = 0;
			alpha_0[k][1] = 0;
		}
		else {
			tmp = 1.0f/ac.r11[0];
			alpha_0[k][0] = -(ac.r01[0]+(alpha_1[k][0]*ac.r12[0])+(alpha_1[k][1]*ac.r12[1]))*tmp;
			alpha_0[k][1] = -(ac.r01[1]+(alpha_1[k][1]*ac.r12[0])-(alpha_1[k][0]*ac.r12[1]))*tmp;
		}

		if(((alpha_0[k][0]*alpha_0[k][0])+(alpha_0[k][1]*alpha_0[k][1])>=16.0f)
			||((alpha_1[k][0]*alpha_1[k][0])+(alpha_1[k][1]*alpha_1[k][1])>=16.0f)) {
			alpha_0[k][0] = 0;
			alpha_0[k][1] = 0;
			alpha_1[k][0] = 0;
			alpha_1[k][1] = 0;
		}
	}
private static void calc_prediction_coef(SBR sbr, float[][][] Xlow,
		float[][] alpha_0, float[][] alpha_1, int k) {
		float tmp;
		acorr_coef ac = new acorr_coef();

		auto_correlation(sbr, ac, Xlow, k, sbr.numTimeSlotsRate+6);

		if(ac.det==0) {
			alpha_1[k][0] = 0;
			alpha_1[k][1] = 0;
		}
		else {
			tmp = 1.0f/ac.det;
			alpha_1[k][0] = ((ac.r01[0]*ac.r12[0])-(ac.r01[1]*ac.r12[1])-(ac.r02[0]*ac.r11[0]))*tmp;
			alpha_1[k][1] = ((ac.r01[1]*ac.r12[0])+(ac.r01[0]*ac.r12[1])-(ac.r02[1]*ac.r11[0]))*tmp;
		}

		if(ac.r11[0]==0) {
			alpha_0[k][0] = 0;
			alpha_0[k][1] = 0;
		}
		else {
			tmp = 1.0f/ac.r11[0];
			alpha_0[k][0] = -(ac.r01[0]+(alpha_1[k][0]*ac.r12[0])+(alpha_1[k][1]*ac.r12[1]))*tmp;
			alpha_0[k][1] = -(ac.r01[1]+(alpha_1[k][1]*ac.r12[0])-(alpha_1[k][0]*ac.r12[1]))*tmp;
		}

		if(((alpha_0[k][0]*alpha_0[k][0])+(alpha_0[k][1]*alpha_0[k][1])>=16.0f)
			||((alpha_1[k][0]*alpha_1[k][0])+(alpha_1[k][1]*alpha_1[k][1])>=16.0f)) {
			alpha_0[k][0] = 0;
			alpha_0[k][1] = 0;
			alpha_1[k][0] = 0;
			alpha_1[k][1] = 0;
		}
	}
/* calculate linear prediction coefficients using the covariance method