Decimation

Abstract: The basic concepts and building blocks in multirate digital signal processing (DSP), including the digital polyphase representation, are reviewed. Recent progress, as reported by several authors in this area, is discussed. Several applications are described, including subband coding of waveforms, voice privacy systems, integral and fractional sampling rate conversion (such as in digital audio), digital crossover networks, and multirate coding of narrowband filter coefficients. The M-band quadrature mirror filter (QMF) bank is discussed in considerable detail, including an analysis of various errors and imperfections. Recent techniques for perfect signal reconstruction in such systems are reviewed. The connection between QMF banks and other related topics, such as block digital filtering and periodically time-varying systems, is examined in a pseudo-circulant-matrix framework. Unconventional applications of the polyphase concept are discussed. >

Abstract: 1. Sampling and Reconstruction. 2. Quantization. 3. Discrete-Time Systems. 4. FIR Filtering and Convolution. 5. z-Transforms. 6. Transfer Functions. 7. Digital Filter Realizations. 8. Signal Processing Applications. 9. DFT/FFT Algorithms. 10. FIR Digital Filter Design. 11. IIR Digital Filter Design. 12. Interpolation, Decimation, and Oversampling. 13. Appendices. References. Index.

Abstract: The concepts of digital signal processing are playing an increasingly important role in the area of multirate signal processing, i.e. signal processing algorithms that involve more than one sampling rate. In this paper we present a tutorial overview of multirate digital signal processing as applied to systems for decimation and interpolation. We first discuss a theoretical model for such systems (based on the sampling theorem) and then show how various structures can be derived to provide efficient implementations of these systems. Design techniques for the linear-time-invariant components of these systems (the digital filter) are discussed, and finally the ideas behind multistage implementations for increased efficiency are presented.

Abstract: This paper deals with applications of Quadrature Mirror Filters (QMF) to coding of voice signal in sub-bands. Use of QMF's enables to avoid the aliasing effects due to samples decimation when signal is split into sub-bands. Each sub-band is then coded independently with use of Block Companded PCM (BCPCM) quantizers. Then a variable number of bits is allocated to each sub-band quantizer in order to take advantage of the relative perceptual effect of the quantizing error. The paper is organized as follows: - First, splitting in two sub-bands with QMF's is analysed. -Then, a general description of a splitband voice coding scheme using QMF's is made. -Finally, two coding schemes are considered, operating respectively at 16 KBps and 32 KBps. Averaged values of S/N performances are given when encoding both male and female voices. Comparisons are made with conventional BCPCM and CCITT A-Law. Taped results will be played at the conference.