Dept. of Electron. Eng., City Polytech. of Hong Kong.
IEEE Trans Image Process. 1992;1(3):312-21. doi: 10.1109/83.148605.
A technique for reducing the complexity of spatial-domain image vector quantization (VQ) is proposed. The conventional spatial domain distortion measure is replaced by a transform domain subspace distortion measure. Due to the energy compaction properties of image transforms, the dimensionality of the subspace distortion measure can be reduced drastically without significantly affecting the performance of the new quantizer. A modified LBG algorithm incorporating the new distortion measure is proposed. Unlike conventional transform domain VQ, the codevector dimension is not reduced and a better image quality is guaranteed. The performance and design considerations of a real-time image encoder using the techniques are investigated. Compared with spatial domain a speed up in both codebook design time and search time is obtained for mean residual VQ, and the size of fast RAM is reduced by a factor of four. Degradation of image quality is less than 0.4 dB in PSNR.
提出了一种降低空域图像矢量量化（VQ）复杂度的技术。用变换域子空间失真测度取代传统的空域失真测度。由于图像变换的能量集中特性，在不显著影响新量化器性能的情况下，子空间失真测度的维数可以大大降低。提出了一种结合新失真测度的改进 LBG 算法。与传统的变换域 VQ 不同，码矢量维数没有减少，并且保证了更好的图像质量。研究了使用这些技术的实时图像编码器的性能和设计考虑因素。与空域相比，平均残差 VQ 的码本设计时间和搜索时间都得到了加快，快速 RAM 的大小减小了四倍。PSNR 中的图像质量下降小于 0.4dB。
