Adaptive sub-band DCT coding for HDTV signal transmission

摘要

This paper presents an adaptive sub-band DCT coding for high-quality HDTV signal transmission. In the coder, the first stage quadrature mirror filters (QMFs) decompose the input signal into two bands in the horizontal direction, while the second stage filters decompose the two bands into four bands in the vertical direction. An adaptive DCT is adopted for horizontal-low and vertical-low (LL) signal coding. To maximize bit-rate reduction efficiency, this paper proposed adaptive selection of the input signal mode to the DCT coding from the intra-field signal as well as the inter-field and motion compensated inter-frame signals. One-dimensional DPCM coding is applied to the signals on the same horizontal line of the LH band. The other-band signals are coded by PCM having a dead zone. To further reduce information bit-rates, variable length coding and run-length coding are applied to the quantized signal in each band. Computer simulation results are presented in terms of bit-per-pel and SNR of the reconstructed picture. This paper also presents codec characteristics when it is connected in tandem. It focuses mainly on causes of quantization-noise accumulation in digital tandem connections which are essential to coding algorithms. A coder configuration that reduces noise accumulation to less than 1 dB after three tandem links is proposed.