Efficient design of a parallel graphic equalizer

Accurate design of a parallel graphic equalizer involves the construction of a complex target frequency response, which is obtained by interpolating smoothly between command gains and by assigning minimum-phase characteristics, followed by a least squares filter design. This work proposes two methods to simplify the computations involved in the design. First, the magnitude and phase response of the target is computed as a combination of minimum-phase basis functions, which leads to the easier evaluation of the total frequency response. The second improvement consists in using the QR decomposition to simplify a matrix inversion required in the design. A comparison with the previous method shows that the accuracy of the proposed design method is not compromised significantly, whereas the computational cost is radically reduced, making the new algorithm highly attractive for interactive audio applications. The method has been tested on an ARM-based System-on-Chip Cortex-A7, which is currently used in mobile devices.