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A CU-Level Rate and Distortion Estimation Scheme for RDO of Hardware-Friendly HEVC Encoders Using Low-Complexity Integer DCTs

机译:使用低复杂度整数DCT的硬件友好型HEVC编码器RDO的CU级速率和失真估计方案

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In this paper, a low complexity coding unit (CU)-level rate and distortion estimation scheme is proposed for High Efficiency Video Coding (HEVC) hardware-friendly implementation where a Walsh–Hadamard transform (WHT)-based low-complexity integer discrete cosine transform (DCT) is employed for distortion estimation. Since HEVC adopts quadtree structures of coding blocks with hierarchical coding depths, it becomes more difficult to estimate accurate rate and distortion values without actually performing transform, quantization, inverse transform, de-quantization, and entropy coding. Furthermore, DCT for rate-distortion optimization (RDO) is computationally high, because it requires a number of multiplication and addition operations for various transform block sizes of 4-, 8-, 16-, and 32-orders and requires recursive computations to decide the optimal depths of CU or transform unit. Therefore, full RDO-based encoding is highly complex, especially for low-power implementation of HEVC encoders. In this paper, a rate and distortion estimation scheme is proposed in CU levels based on a low-complexity integer DCT that can be computed in terms of WHT whose coefficients are produced in prediction stages. For rate and distortion estimation in CU levels, two orthogonal matrices of and , which are applied to WHT that are newly designed in a butterfly structure only with addition and shift operations. By applying the integer DCT based on the WHT and newly designed transforms in each CU block, the texture rate can precisely be estimated after quantization using the number of non-zero quantized coefficients and the distortion can also be precisely estimated in transform domain without de-quantization and inverse transform required. In addition, a non-texture rate estimation is proposed by using a pseudoentr- py code to obtain accurate total rate estimates. The proposed rate and the distortion estimation scheme can effectively be used for HW-friendly implementation of HEVC encoders with 9.8% loss over HEVC full RDO, which much less than 20.3% and 30.2% loss of a conventional approach and Hadamard-only scheme, respectively.
机译:本文针对高效率视频编码(HEVC)的硬件友好实现提出了一种低复杂度编码单元(CU)级速率和失真估计方案,其中基于Walsh-Hadamard变换(WHT)的低复杂度整数离散余弦变换(DCT)用于失真估计。由于HEVC采用具有分层编码深度的编码块的四叉树结构,因此在不实际执行变换,量化,逆变换,解量化和熵编码的情况下,估计准确的速率和失真值变得更加困难。此外,用于速率失真优化(RDO)的DCT在计算上很高,因为它需要对4、8、16和32阶各种变换块大小进行许多乘法和加法运算,并且需要递归计算才能确定CU或变换单元的最佳深度。因此,完全基于RDO的编码非常复杂,尤其是对于HEVC编码器的低功耗实现而言。在本文中,提出了一种基于低复杂度整数DCT的CU级速率和失真估计方案,该DCT可以根据WHT来计算,而WHT的系数是在预测阶段产生的。对于CU级别的速率和失真估计,两个正交矩阵和应用于WHT,这两个矩阵仅通过加法和移位运算才以蝶形结构重新设计。通过基于WHT和新设计的变换在每个CU块中应用整数DCT,可以在量化后使用非零量化系数的数量精确估计纹理率,并且还可以在变换域中精确估计失真,而无需进行需要量化和逆变换。另外,通过使用伪密码来获得准确的总速率估计,提出了一种非纹理速率估计。所提出的速率和失真估计方案可以有效地用于HEVC编码器的硬件友好实现,其损失要比HEVC完整RDO损失9.8%,分别远低于传统方法和仅Hadamard方案的20.3%和30.2%损失。 。

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