A locally adaptive perceptual masking threshold model for image coding

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1994.Includes bibliographical references (leaves 95-97).by Trac Duy Tran.M.S

Communication channel analysis and real time compressed sensing for high density neural recording devices

Next generation neural recording and Brain- Machine Interface (BMI) devices call for high density or distributed systems with more than 1000 recording sites. As the recording site density grows, the device generates data on the scale of several hundred megabits per second (Mbps). Transmitting such large amounts of data induces significant power consumption and heat dissipation for the implanted electronics. Facing these constraints, efficient on-chip compression techniques become essential to the reduction of implanted systems power consumption. This paper analyzes the communication channel constraints for high density neural recording devices. This paper then quantifies the improvement on communication channel using efficient on-chip compression methods. Finally, This paper describes a Compressed Sensing (CS) based system that can reduce the data rate by > 10x times while using power on the order of a few hundred nW per recording channel

Linear Phase Perfect Reconstruction Filter Banks: Theory, Structure, Design, And Application In Image Compression

This dissertation studies the theory, structure, design, and implementation of discretetime FIR linear phase perfect reconstruction filter banks with arbitrary M channels and arbitrary-length filters. The class of filter banks in consideration has high practical values, and the results reported are the most general solutions in the current literature. The approach consistently taken throughout the dissertation is to parameterize these systems by lattice structures based on the factorizations of the analysis and synthesis polyphase transfer matrices. The lattice robustly enforces the two most desirable properties, namely linear phase and perfect reconstruction, so that they are inherently retained regardless of the quantization of lattice coefficients to any desired level. The various lattices are proven to completely span the set of all possible solutions and to employ the least number of delay elements in the filter bank's implementation. The novel multi-band linear phase perfect reco..

A Locally Adaptive Perceptual Masking Threshold Model for Image Coding

This project involved designing, implementing, and testing of a locally adaptive perceptual masking threshold model for image compression. This model computes, based on the contents of the original images, the maximum amount of noise energy that can be injected at each transform coefficient that results in perceptually distortion-free still images or sequences of images. The adaptive perceptual masking threshold model can be used as a pre-processor to a JPEG compression standard image coder. DCT coefficients less than their corresponding perceptual thresholds can be set to zero before the normal JPEG quantization and Huffman coding steps. The result is an image-dependent gain in the bit rate needed for transparent coding. In an informal subjective test involving 318 still images in the AT&T Bell Laboratory image database, this model provided a gain on the order of 10 to 30 %. Thesis Supervisor: Robert J. Safranek Title: Member of Technical Staff, AT&T Bell Laboratory Thesis Supervisor:..

On-Channel Linear Phase FIR Filter Banks and Application in Image Compression

Abstract—This paper investigates the theory and structure of a large subclass of w-channel linear-phase perfect-reconstruction FIR filter banks—systems with analysis and synthesis filters of length v � a u�w C, where is an arbitrary interger, H ` w, and u � is any positive interger. For this subclass of systems, we first investigate the necessary conditions for the existence of linear-phase perfect-reconstruction filter banks (LPPRFB’s). Next, we develop a complete and minimal factorization for all even-channel linear-phase paraunitary systems (the most general lapped orthogonal transforms to date). Finally, several design examples as well as comparisons with previous generalized lapped orthogonal transforms (GenLOT’s) in image compression are presented to confirm the validity of the theory. I