Fast ISP Coding Mode Optimization Algorithm Based on CU Texture Complexity for VVC

Abstract

In lately published video coding standard Versatile Video Coding (VVC/ H.266), the intra sub-partitions (ISP) coding mode is proposed. It is efficient for frames with rich texture, but less efficient for frames that are very flat or constant. In this paper, by comparing and analyzing the rate distortion cost (RD-cost) of coding unit (CU) with different texture features for using and not using ISP(No-ISP) coding mode, it is found that CUs with simple texture can get better coding performance in No-ISP coding mode. Based on this observations, a fast ISP coding mode optimization algorithm based on CU texture complexity is proposed, which aims to determine whether CU needs to use ISP coding mode in advance by calculating CU texture complexity, so as to reduce the computation complexity of ISP. The experimental results show that under All Intra (AI) configuration, the coding time can be reduced by 7%, while the BD-rate only increase by 0.09%.

Machine Learning-Based Early Skip Decision for Intra Subpartition Prediction in VVC

“…In the class F, which is screen content videos, TABLE 12. Performance comparison of the proposed method with existing works [19], [20] against anchor VTM11.0. many blocks select Intra-Block Copy (IBC) and Transform skip Mode which are not integrated with ISP [45].…”

“…To understand the performance of our proposed method more fairly, we also compare it with the existing works [19], [20]. Table 12 shows the overall performance comparison between our work in this paper and the existing methods in [19], [20], which were implemented on VTM11.0.…”

“…In other words, if a block is not predicted using closer reference samples by ISP, its ISP mode test is skipped to make the encoder faster. An optimization scheme for fast ISP coding mode is also proposed based on the CU texture complexity [20], [21], [22]. They measure the CU block texture complexity to determine whether a CU needs to use the ISP mode or not, so as to achieve faster encoding.…”

“…They measure the CU block texture complexity to determine whether a CU needs to use the ISP mode or not, so as to achieve faster encoding. We note that previous fast ISP decision approaches [19], [20], [21], [22] can reduce the overall encoding time by effectively avoiding unnecessary rate distortion optimization (RDO) processes by fast intra mode decision through characterization of the information of each block. However, we also note that those previous approaches [19], [20], [21], [22] considered only the intra prediction direction and the texture of the block itself; that is, they missed due consideration of the benefit of performing separate transforms for each subpartition.…”

“…Dong et al [22] used decision tree (DT) [37] model for designing a fast ISP mode skip method. But only CU texture complexity is considered as in previous works [19], [20], [21]. While the goal of this paper is to design a fast ISP search scheme (the same goal as previous approaches), the proposed ISP Early Skip Decision (ISP-ESD) scheme also makes early determinations on whether or not to test ISP mode in the RDO process by considering the efficiency facilitated by ISP prediction and transforming each subpartition individually.…”