Energy-Efficient 8-Point DCT Approximations: Theory and Hardware Architectures

Due to its remarkable energy compaction properties, the discrete cosine transform (DCT) is employed in a multitude of compression standards, such as JPEG and H.265/HEVC. Several low-complexity integer approximations for the DCT have been proposed for both 1D and 2D signal analyses. The increasing demand for low-complexity, energy-efficient methods requires algorithms with even lower computational costs. In this paper, new 8-point DCT approximations with very low arithmetic complexity are presented. The new transforms are proposed based on pruning state-of-the-art DCT approximations. The proposed algorithms were assessed in terms of arithmetic complexity, energy retention capability, and image compression performance. In addition, a metric combining performance and computational complexity measures was proposed. Results showed good performance and extremely low computational complexity. Introduced algorithms were mapped into systolic-array digital architectures and physically realized as digital prototype circuits using FPGA technology and mapped to 45 nm CMOS technology. All hardware-related metrics showed low resource consumption of the proposed pruned approximate transforms. The best proposed transform according to the introduced metric presents a reduction in power consumption of 21–25 %.     

A multiplierless pruned DCT-like transformation for image and video compression that requires ten additions only

A multiplierless pruned approximate eight-point discrete cosine transform (DCT) requiring only ten additions is introduced. The proposed algorithm was assessed in image and video compression, showing competitive performance with state-of-the-art methods. Digital synthesis in 45 nm CMOS technology up to place-and-route level indicates clock speed of 288 MHz at a 1.1 V supply. The \(8\times 8\) block rate is 36 MHz. The DCT approximation was embedded into HEVC reference software; resulting video frames, at up to 327 Hz for 8-bit RGB HEVC, presented negligible image degradation.     

Foliar micromorphology and its role in identification of the Apocynaceae taxa

In the present study, we evaluate the importance of foliar epidermal micromorphological characteristics of Apocyanaceae for accurate identification and classification. The species were collected from the University of Peshawar's main campus in the spring season to observe its qualitative and quantitative features. The length and width of guard cells, stomatal pore and subsidiary cells, trichomes, and crypts on both sides of the leaf were examined. Many species were observed to be hypostomatic. Plumeria rubra, Raulfia serpentine, Thevetia peruviana, Trachelospermum lucidum, Alstonia scholaris, and Catharanthus roseus demonstrated hypostomatic leaves. Nearly all the investigated species had anisocytic type of stomata only or in combination with other types of stomata on the upper and lower epidermis. Carissa carandas had anomocytic, anisocytic, and cyclocytic type of stomata on the upper epidermis, and the lower epidermis showed variations in stomatal type, such as anomocytic, stephanocytic, brachyparacytic, and hemiparacytic. Nerium oleander had no specific shape of stomata but showed stomatal crypts in which the stomata were enclosed inside many trichomes. The taxonomic key based on stomatal types, epidermal cells, stomatal index value, and statistical analysis, along with the variations in the epidermal cells, shows the link between the selected plants species, which will provide a baseline for future anatomical studies. This study highlights many undocumented micromorphological characteristics. The anatomical characteristics observed in this study will be helpful for taxonomic identification and species delimitation of the family Apocynaceae.