基于非均匀量化的小波域分布式深度图视频编码

针对分布式多视点加深度格式(DMVD)的视频编码中深度图视频解码质量问题,提出一种结合子带层及子带系数的小波域分布式深度视频非均匀量化方案,通过给边缘分配更多比特来提升深度图的边缘质量。结合深度图经小波变换后系数分布特性,对第N层的低频小波系数采用均匀量化方案,对其他层高频小波系数采用非均匀量化方案。针对高频系数的非均匀量化,对处于"0"左右的高频系数采用较大的量化步长,随着高频系数幅度值的增大,量化步长逐渐减小,量化逐渐精细,从而提升深度图中的边缘细节质量。实验结果表明,对于边缘较多且变化较明显的"Dancer"和"PoznanHall2"深度序列,该算法能够有效地提高二者的边缘信息质量从而提高其率失真(R-D)性能,最高可达1.2 dB;而对于边缘区域较小且较为模糊的"Newspaper"和"Balloons"深度序列,系统的R-D性能也能被提升0.3 dB左右。

Wavelet domain distributed depth map video coding based on non-uniform quantization

In order to improve the decoding quality of depth map video in Distributed Multi-view Video plus Depth (DMVD) coding, a new non-uniform quantization scheme based on the sub-band layer and sub-band coefficients was proposed in wavelet domain Distributed Video Coding (DVC). The main idea was allocating more bits to pixels belong to the edge of depth map and consequently improving the quality of the depth map. According to the distribution characteristics of the wavelet coefficients of depth map, the low frequency wavelet coefficients of layer-N kept the uniform quantization scheme, while the high frequency wavelet coefficients of all layers used the non-uniform quantization scheme. For the high frequency wavelet coefficients around "0", larger quantization step was adopted. As the amplitude of the high frequency wavelet coefficients increased, the quantization step decreased, with finer quantization and the quality of the edge was improved consequently. The experimental results show that, for "Dancer" and "PoznanHall2" depth sequence with more edges, the proposed scheme can achieve up to 1.2 dB in terms of the Rate-Distortion (R-D) performance improvement by improving the quality of edges; for "Newspaper" and "Balloons" depth sequences with less edges, the proposed scheme can still get 0.3 dB of the R-D performance.