Low-Complexity Loeffler DCT Approximations for Image and Video Coding

This paper introduced a matrix parametrization method based on the Loeffler discrete cosine transform (DCT) algorithm. As a result, a new class of eight-point DCT approximations was proposed, capable of unifying the mathematical formalism of several eight-point DCT approximations archived in the literature. Pareto-efficient DCT approximations are obtained through multicriteria optimization, where computational complexity, proximity, and coding performance are considered. Efficient approximations and their scaled 16- and 32-point versions are embedded into image and video encoders, including a JPEG-like codec and H.264/AVC and H.265/HEVC standards. Results are compared to the unmodified standard codecs. Efficient approximations are mapped and implemented on a Xilinx VLX240T FPGA and evaluated for area, speed, and power consumption.

Block-Parallel Systolic-Array Architecture for 2-D NTT-based Fragile Watermark Embedding

Number-theoretic transforms (NTTs) have been applied in the fragile watermarking of digital images. A block-parallel systolic-array architecture is proposed for watermarking based on the 2-D special Hartley NTT (HNTT). The proposed core employs two 2-D special HNTT hardware cores, each using digital arithmetic over $\mathrm{GF}(3)$, and processes $4\times4$ blocks of pixels in parallel every clock cycle. Prototypes are operational on a Xilinx Sx35-10ff668 FPGA device. The maximum estimated throughput of the FPGA circuit is 100 million $4\times4$ HNTT fragile watermarked blocks per second, when clocked at 100 MHz. Potential applications exist in high-traffic back-end servers dealing with large amounts of protected digital images requiring authentication, in remote-sensing for high-security surveillance applications, in real-time video processing of information of a sensitive nature or matters of national security, in video/photographic content management of corporate clients, in authenticating multimedia for the entertainment industry, in the authentication of electronic evidence material, and in real-time news streaming.