Johnston Filters and Optimal SNR in Maximally Decimated Filter Banks
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Abstract
In the design of maximally decimated filter banks, conventional practice is to use Johnston filters at both the analysis and synthesis ends. This paper proposes a two-step procedure: First, select suitable Johnston filters for the analysis side for good coding of the input; then design the synthesis filters to optimize the signal to reconstructed noise ratio SNR. A detailed example shows that one can do somewhat better than Johnston filters at the synthesis end. 1 Introduction This paper concerns the maximally decimated filter bank in Figure 1. The analysis filters are typically frequency selective: H 0 lowpass and H 1 highpass. Such systems are used in subband coding and decoding of speech, images, and video for transmission and storage. Subband coders have been adopted in many new international coding standards [1]. Even though the analysis and synthesis filters are linear time-invariant (LTI), the overall system is in general a linear periodically time-varying (LPTV) system because..