public void coeff(double[][] dct_coef, int n) {
		double sqrt_1 = 1.0 / Math.sqrt(2.0);
		for (int i = 0; i < n; i++) {
			dct_coef[0][i] = sqrt_1;
		}
		//Initialize coefficient 
		for (int i = 1; i < n; i++) {
			for (int j = 0; j < n; j++) {
				dct_coef[i][j] = this.a* Math.cos(i * Math.PI * (j + 0.5) / ((double) n));
			}
		}
	}