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Compression
Published in John Watkinson, An Introduction to Digital Audio, 2013
The bandsplitting process is complex and requires a lot of computation. One bandsplitting method which is useful is quadrature mirror filtering.15 The QMF is a kind of twin FIR filter which converts a PCM sample stream into to two sample streams of half the input sampling rate, so that the output data rate equals the input data rate. The frequencies in the lower half of the audio spectrum are carried in one sample stream, and the frequencies in the upper half of the spectrum are carried in the other. Whilst the lower-frequency output is a PCM band-limited representation of the input waveform, the upper frequency output isn’t. A moment’s thought will reveal that it could not be so because the sampling rate is not high enough. In fact the upper half of the input spectrum has been heterodyned down to the same frequency band as the lower half by the clever use of aliasing. The waveform is unrecognizable, but when heterodyned back to its correct place in the spectrum in an inverse step, the correct waveform will result once more.
Compression
Published in John Watkinson, The Art of Digital Audio, 2013
The bandsplitting process is complex and requires a lot of computation. One bandsplitting method which is useful is quadrature mirror filtering.15 The QMF is is a kind of twin FIR filter which converts a PCM sample stream into to two sample streams of half the input sampling rate, so that the output data rate equals the input data rate. The frequencies in the lower half of the audio spectrum are carried in one sample stream, and the frequencies in the upper half of the spectrum are carried in the other. Whilst the lower-frequency output is a PCM band-limited representation of the input waveform, the upper frequency output isn't. A moment's thought will reveal that it could not be so because the sampling rate is not high enough. In fact the upper half of the input spectrum has been heterodyned down to the same frequency band as the lower half by the clever use of aliasing. The waveform is unrecognizable, but when heterodyned back to its correct place in the spectrum in an inverse step, the correct waveform will result once more.
Audio signal processing
Published in John Watkinson, The Art of Sound Reproduction, 2012
The band-splitting process is complex and requires a lot of computation. One band-splitting method which is useful is quadrature mirror filtering (QMF).15 The QMF is a kind of twin FIR filter which converts a PCM sample stream into two sample streams of half the input sampling rate, so that the output data rate equals the input data rate. The frequencies in the lower half of the audio spectrum are carried in one sample stream, and the frequencies in the upper half of the spectrum are carried in the other. Whilst the lower frequency output is a PCM band-limited representation of the input waveform, the upper frequency output is not. A moment's thought will reveal that it could not be because the sampling rate is not high enough. In fact the upper half of the input spectrum has been heterodyned down to the same frequency band as the lower half by the clever use of aliasing. The waveform is unrecognizable, but when heterodyned back to its correct place in the spectrum in an inverse step, the correct waveform will result once more.
A new method for designing multiplierless two-channel filterbank using shifted-Chebyshev polynomials
Published in International Journal of Electronics, 2019
During the last four decades, a two-channel filterbank has been classified as the basic component in multirate signal processing due to its feature of dividing a signal into two sub-sets of signals for individual processing or compositing these sub-set signals into a single one. It is also known as a quadrature mirror filter (QMF) bank and hence most widely preferred in numerous applications of signal and image processing. All these applications rely on the design accuracy and hardware requirement of a filterbank. Therefore, several attempts have been made for efficient design of a filterbank during the past research (Kong, Xia, Jiang, & Gao, 2014; Kumar, Singh, & Anand, 2011; Lin, 2017; Poudereux, Hernández, Mateos, Pinto-Benel, & Cruz-Roldán, 2016), and it is still an open-end research problem. A generalized representation of a two-channel filterbank is depicted in Figure 1 (Kumar, Singh, & Anand, 2013). In this structure, H0(z) and H1(z) stand for the low-pass and high-pass analysis filters, respectively, while G0(z) and G1(z) represent the low-pass and high-pass synthesis filters, respectively.
Wavelet OFDM-Based Non-orthogonal Multiple Access Downlink Transceiver for Future Radio Access
Published in IETE Technical Review, 2018
The main difference between discrete Fourier transform (DFT) and CMT based OFDM lies in the fact that in DFT filter-bank, , whereas for CMT filter-bank, . For a critically sampled CMT, where , the modulated copies of filter-banks are generated as [19]where is the prototype filter. The demodulated filter-bank with reference to modulated filter-bank is given as [19]For our proposed transceiver, wavelet filter-banks as CMT are implemented in the form of octave spaced or two channel tree structure. In tree structure, low pass filter (LPF) and high pass filter (HPF) are used to decompose the incoming data into two sub-bands and then down-sampled by two. The low passed data is iterated through the same filtering process. Such structure is also called quadrature mirror filter-bank (QMF) because of the complementary relation between LPF and HPF. Thus, for our proposed architecture, to achieve the low complexity of the design process, PR-QMF with cosine modulation is proposed. Filter-banks are implemented with different types of MA techniques to encounter multipath effects on the data transmission.
Quadrature mirror filter bank design based on hybrid bee colony technique
Published in Automatika, 2021
Hitendra Singh, Atul Kumar Dwivedi, Deepak Nagaria
The design of QMF bank received the attention due to their importance in the numerous applications of digital signal processing. In signal processing systems, QMF bank provides number of advantages such as removal of aliasing distortion, wider bandwidth and lower bit rates without degrading quality of output signal. Because of these advantages, QMF bank is used in multi-tone modulation systems [1], sub band coding of speech [2], analog to digital conversion [3], image processing [4], multiplexers [5], two-dimensional short time spectral analysis [6], design of wavelet bases [7, 8], antenna system [9], biomedical signal processing [10], wireless communication for noise cancellation [11] and wide-band beam-forming forsonar [12].