In AOMedia Video 1 (AV1), directional intra prediction modes are applied to model local texture patterns that present certain directionality. Each intra prediction direction is represented with a nominal mode index an...
详细信息
ISBN:
(纸本)9781728176055
In AOMedia Video 1 (AV1), directional intra prediction modes are applied to model local texture patterns that present certain directionality. Each intra prediction direction is represented with a nominal mode index and a delta angle. The delta angle is entropy coded using shared context between luma and chroma, and the context is derived using the associated nominal mode. In this paper, two methods are proposed to further reduce the signaling cost of delta angles: cross-component delta angle coding, and context-adaptive delta angle coding, whereby the cross-component and spatial correlation of the delta angles are explored, respectively. The proposed methods were implemented on top of a recent version of libaom. Experimental results show that the proposed cross-component delta angle coding achieved average 0.4% BD-rate reduction with 4% encoding time saving over all intra configurations. By combining both methods, an average 1.2% BD-rate reduction is achieved.
HEVC utilizes 35 intra prediction modes to predict each luma block. To ensure the selected mode for a luma block is signaled with minimal overhead, HEVC defines a set of three most probable modes (MPM), which are deri...
详细信息
ISBN:
(纸本)9781538663189
HEVC utilizes 35 intra prediction modes to predict each luma block. To ensure the selected mode for a luma block is signaled with minimal overhead, HEVC defines a set of three most probable modes (MPM), which are derived based on the modes of its two neighbors. If the intra prediction mode is not one of these three most probable modes, it is coded as one of the remaining modes using a longer codeword. To improve the efficiency of intra prediction modecoding further, this paper presents a method to derive a second set of most probable modes, by using neighboring reconstructed samples. One line of reference samples is used as the original pixels and predicted by another line of reference samples. The sum of absolute differences (SAD) is employed as a measurement to select several modes with minimum SADs as the second MPM set. Experimental results show that for all intra configurations, the proposed method achieves on average 0.54%, 0.34%, and 0.34% BD-rate reductions for Y, U and V, respectively.
In VVC, the intra prediction mode of a block is encoded using the most probable mode (MPM). For this purpose, possible candidate modes for MPM are maintained in the MPM candidate list. The list is constructed differen...
详细信息
ISBN:
(数字)9781510679931
ISBN:
(纸本)9781510679931;9781510679924
In VVC, the intra prediction mode of a block is encoded using the most probable mode (MPM). For this purpose, possible candidate modes for MPM are maintained in the MPM candidate list. The list is constructed differently depending on the number of neighboring angular intra prediction modes. While it is important to maintain a proper MPM candidate list, but how to encode the selected list index is also important. In this paper, we investigate on context coding of the MPM candidate list index instead of the current bypass-coding in VVC. The proposed method achieves a BDBR gain of 0.08% in the Y channel, and 0.10% and 0.06% respectively in the Cb and Cr channels.
暂无评论