Zhang Yun, Zhu Linwei, Hamzaoui Raouf, Kwong Sam, Ho Yo-Sung
IEEE Trans Image Process. 2021;30:402-417. doi: 10.1109/TIP.2020.3036760. Epub 2020 Nov 23.
Mismatches between the precisions of representing the disparity, depth value and rendering position in 3D video systems cause redundancies in depth map representations. In this paper, we propose a highly efficient multiview depth coding scheme based on Depth Histogram Projection (DHP) and Allowable Depth Distortion (ADD) in view synthesis. Firstly, DHP exploits the sparse representation of depth maps generated from stereo matching to reduce the residual error from INTER and INTRA predictions in depth coding. We provide a mathematical foundation for DHP-based lossless depth coding by theoretically analyzing its rate-distortion cost. Then, due to the mismatch between depth value and rendering position, there is a many-to-one mapping relationship between them in view synthesis, which induces the ADD model. Based on this ADD model and DHP, depth coding with lossless view synthesis quality is proposed to further improve the compression performance of depth coding while maintaining the same synthesized video quality. Experimental results reveal that the proposed DHP based depth coding can achieve an average bit rate saving of 20.66% to 19.52% for lossless coding on Multiview High Efficiency Video Coding (MV-HEVC) with different groups of pictures. In addition, our depth coding based on DHP and ADD achieves an average depth bit rate reduction of 46.69%, 34.12% and 28.68% for lossless view synthesis quality when the rendering precision varies from integer, half to quarter pixels, respectively. We obtain similar gains for lossless depth coding on the 3D-HEVC, HEVC Intra coding and JPEG2000 platforms.
3D视频系统中表示视差、深度值和渲染位置的精度之间的不匹配会导致深度图表示中的冗余。在本文中，我们提出了一种基于深度直方图投影（DHP）和视图合成中允许深度失真（ADD）的高效多视图深度编码方案。首先，DHP利用立体匹配生成的深度图的稀疏表示来减少深度编码中帧间和帧内预测的残余误差。我们通过理论分析基于DHP的无损深度编码的率失真代价，为其提供了数学基础。然后，由于深度值和渲染位置之间的不匹配，在视图合成中它们之间存在多对一的映射关系，这就引出了ADD模型。基于此ADD模型和DHP，提出了具有无损视图合成质量的深度编码，以在保持相同合成视频质量的同时进一步提高深度编码的压缩性能。实验结果表明，所提出的基于DHP的深度编码在不同图像组的多视图高效视频编码（MV-HEVC）上进行无损编码时，平均比特率节省可达20.66%至19.52%。此外，当渲染精度分别从整数像素、半像素变化到四分之一像素时，我们基于DHP和ADD的深度编码在无损视图合成质量下，平均深度比特率分别降低了46.69%、34.12%和28.68%。我们在3D-HEVC、HEVC帧内编码和JPEG2000平台上进行无损深度编码时也获得了类似的增益。
