Abstract
This paper proposes two optimal Cordic Loeffler based DCT (Discrete Cosine Transform algorithm) architectures: a fast and low Power DCT architecture and a high PSNR DCT architecture. The rotation parameters of CORDIC angles required for these architectures have been calculated using a MATLAB script. This script allows the variation of the angle’s precision from 10-1 to 10-4. The experimental results show that the fast and low Power DCT architecture correponds to the precision 10-1. Its complexity is even lower than the BinDCT which is a reference in terms of low complexity and its power has been enhanced in comparison with the conventional Cordic Loeffler DCT by 12 mW. The experimental results also show that the high PSNR DCT architecture corresponds to the precision 10-3 for which the PSNR has been improved by 6.55 dB in comparison with the conventional Cordic Loeffler DCT. Then, the hardware implementation and the generated RTL of some required Cordics are presented.
Highlights
The Discrete Cosine Transform DCT was developed by Ahmed et al in 1974 [1]
The first one consists on the enhancement of the quality of the DCT in terms of precision measured through the Peak Signal to Noise Ratio (PSNR) ([3], [4])
We present two optimal Cordic Loeffler based DCT architectures: a high PSNR architecture (Arch.Deg3) and a fast and low power architecture (Arch.Deg1)
Summary
The Discrete Cosine Transform DCT was developed by Ahmed et al in 1974 [1]. It is a robust approximation of the optimal Karhunen-Loeve Transform (KLT) [2]. The first one consists on the enhancement of the quality of the DCT in terms of precision measured through the Peak Signal to Noise Ratio (PSNR) ([3], [4]) The reference in this case is the Loeffler based DCT which is the most precise architecture since it doesn’t contain approximations. In [9], authors proposed a low-complexity CORDIC based DCT algorithm based on the Flow Graph Algorithm (FGA) which is the commonly used way to represent the fast DCT It requires only 38 add and 16 shift operations and consumes about 26.1 % less power compared to [13],with a minor image quality degradation of 0.04 dB. A new table of parameters is obtained with new choice of the elementary rotations Their experimental result shows that the Cordic-based Loeffler DCT consumes 16% of energy compared to [16] with a minor image quality degradation of 0.03 dB.
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