Design of multichannel filter banks for subband coding of audio signals using multirate signal processing techniques

Aditya Goel

doi:10.1117/12.732301

8 October 2007 Design of multichannel filter banks for subband coding of audio signals using multirate signal processing techniques

Aditya Goel

Author Affiliations +

Proceedings Volume 6700, Mathematics of Data/Image Pattern Recognition, Compression, Coding, and Encryption X, with Applications; 670005 (2007) https://doi.org/10.1117/12.732301
Event: Optical Engineering + Applications, 2007, San Diego, California, United States

Abstract

This paper presents a design technique for multi channel filter banks for subband coding of audio signal. In sub-band coding, the speech is first split into frequency bands using a bank of bandpass filters. The individual band pass signals are then decimated by a factor 'N' and encoded for transmission. A filter bank is a collection of bandpass filters, all processing the same input signal. The important parameters in sub-band coders are the number of frequency bands and the frequency range of the system, and the sub-band coding technique. The total number of filters required are 2N. The sub-band signals can be reconstructed perfectly with linear-phase FIR filters. The filter bank is designed so as to overcome the effect of non-ideal transition-band and stop-bands filtering. With real-world filters, the non-zero signal energy in the transition and stop bands is reflected back into the pass-band during the interpolation process at the receiver causing aliasing. This aliasing is canceled in the filter bank during reconstruction of the signal. This paper deals with the designing of 8 band filter banks and coding the subband signals at various bit rates using DPCM technique. In this we used a sampling rate of 44.1Khz. The first two bands are coded at 8 bits/sample, next three bands are coded at 4bits/sample and last 3 bands are coded at 2 bits/sample. Lower frequency spectrum is encoded at higher bit rate, as more energy is concentrated in the lower range. Simulated results using MATLAB Software shows that a compression ratio of 3.76:1 is achieved with perceptual quality. Beyond this we find that the signal quality degraded to reasonable extent, which is not recommended. There has to be a tradeoff between the compression ratio and Quality of transmitted signal.

Citation Download Citation

Aditya Goel "Design of multichannel filter banks for subband coding of audio signals using multirate signal processing techniques", Proc. SPIE 6700, Mathematics of Data/Image Pattern Recognition, Compression, Coding, and Encryption X, with Applications, 670005 (8 October 2007); https://doi.org/10.1117/12.732301

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