Arbitrarily shaped sub-block motion prediction in texture map compression using depth information
Arbitrarily shaped sub-block motion prediction in texture map compression using depth information
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DOI：
10.1109/pcs.2012.6213301
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发表时间：
2012-05
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通讯作者：
Ismaël Daribo;D. Florêncio;Gene Cheung
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作者：
Ismaël Daribo;D. Florêncio;Gene Cheung
在传输所谓的“纹理+深度”的视频格式时，来自同一视点的纹理和深度贴图显示出高度的相关性。然后，来自一个映射的编码比特可以用作边信息来编码另一个映射。本文提出利用深度信息将纹理映射图中的相应块划分为任意形状的区域(子块)，分别用于运动估计和运动补偿。在H.264中，我们使用深度信息作为一种新的编码模式(z模式)，实现了我们提出的用于纹理映射编码的子块运动预测(MP)方法。然而，在实际实验中，人们可以观察到纹理和深度边缘之间的错位，或者纹理边界上的混叠效果。为了解决这个问题，z-MODE提供了两种MC类型：i)非重叠MC和ii)重叠MC。在后一种情况下，使用适当设计的滤波器对ME之后的重叠子块进行阿尔法混合。此外，使用相似深度的相邻块的MV的拉普拉斯加权平均来预测Z模式下每个子块的MV。实验结果表明，在高码率下，使用z模式，纹理映射的编码性能与原生H.264实现相比可以提高0.7dB。
When transmitting the so-called “texture-plus-depth” video format, texture and depth maps from the same viewpoint exhibit high correlation. Coded bits from one map can then be used as side information to encode the other. In this paper, we propose to use the depth information to divide the corresponding block in texture map into arbitrarily shaped regions (sub-blocks) for separate motion estimation (ME) and motion compensation (MC). We implemented our proposed sub-block motion prediction (MP) method for texture map coding using depth information as a new coding mode (z-mode) in H.264. Nonetheless, in practical experiments one can observe either a misalignment between texture and depth edges, or an aliasing effect at the texture boundaries. To overcome this issue, z-mode offers two MC types: i) non-overlapping MC, and ii) overlapping MC. In the latter case, overlapped sub-blocks after ME are alpha-blended using a properly designed filter. Moreover, the MV of each sub-block in z-mode is predicted using a Laplacian-weighted average of MVs of neighboring blocks of similar depth. Experimental results show that using z-mode, coding performance of the texture map can be improved by up to 0.7dB compared to native H.264 implementation at high bitrate.