Analysis/synthesis systems in the presence of quantization

The authors have experimented with a variety of analysis/synthesis systems in the presence of quantization. The systems were block discrete Fourier transform (DFT), block DFT with trapezoidal windowing, block discrete cosine transform, Hanning windowed short-time Fourier transform (STFT) oversampled by a factor of two, Kaiser windowed STFT oversampled by a factor of four, quadrature mirror filter (QMF) banks, perfect-reconstruction QMF banks, pseudo-QMF banks, and Princen-Bradley filter banks. All systems were evaluated for speech compression; a subset was evaluated for image compression. It is shown that for speech the more sophisticated systems (e.g., QMF) provide the best objective performance, but comparable subjective performance can be obtained at a fraction of the complexity using simpler systems (e.g. pseudo-QMF and Princen-Bradley filter banks). For images, a tree-structured QMF bank did not perform well for 16*16 frequency bands when compared to block-oriented analysis/synthesis systems.<
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