A Scalable Approximate DCT Architectures for Efficient HEVC Compliant Video Coding
A Scalable Approximate DCT Architectures for Efficient HEVC Compliant Video Coding
Abstract:
An approximate kernel for the discrete cosine transform (DCT) of length 4 is derived from the 4point DCT defined by the High Efficiency Video Coding (HEVC) standard, and used that for the computation of DCT and inverse DCT (IDCT) of powerof2 lengths. There are two reasons to consider the DCT of length 4 as the basic module. Firstly, it allows to compute DCTs of length 4, 8, 16, and 32 prescribed by HEVC. Moreover, the DCTs generated by 4point DCT not only involve lower complexity but also offer better compression performance. Full-parallel and area-constrained architectures for the proposed approximate DCT are proposed to have flexible trade-off between area and time complexities. Also, a reconfigurable architecture is proposed where 8point DCT can be used for a pair of 4point DCTs. Using the same reconfiguration scheme 32point DCT could be configured for parallel computation of two 16point DCTs or four 8point DCTs or eight 4point DCTs. The proposed reconfigurable design can support real-time coding for high-definition video sequences in the 8K UHDTV format (76804320 @ 30 fps). A unified forward and inverse transform architecture is also proposed where the hardware complexity is reduced by sharing of hardware between DCT and IDCT computation. The proposed approximation has nearly the same arithmetic complexity and hardware requirement as those of recently proposed related methods, but involves significantly less error energy, and offers better PSNR than the others when the DCTs of length more than 8 are used. A detail comparisons of complexity, energy efficiency, and compression performance of different DCT approximation schemes for video coding are also presented. It is shown that the proposed approximation provides better compressed image quality than the other approximate DCT. The proposed method can perform HEVC-compliant video coding with marginal degradation of video quality and slight increase in bit-rate with a fraction of computational complexity of the latter.
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