Showing papers on "Discrete cosine transform published in 1974"

Discrete Cosine Transform

Abstract: A discrete cosine transform (DCT) is defined and an algorithm to compute it using the fast Fourier transform is developed. It is shown that the discrete cosine transform can be used in the area of digital processing for the purposes of pattern recognition and Wiener filtering. Its performance is compared with that of a class of orthogonal transforms and is found to compare closely to that of the Karhunen-Loeve transform, which is known to be optimal. The performances of the Karhunen-Loeve and discrete cosine transforms are also found to compare closely with respect to the rate-distortion criterion.

Comparative Study of a Discrete Linear Basis for Image Data Compression

Abstract: Transform image data compression consists of dividing the image into a number of nonoverlapping subimage regions and quantizing and coding the transform of the data from each subimage. Karhunen-Loeve, Hadamard, and Fourier transforms are most commonly used in transform image compression. This paper presents a new discrete linear transform for image compression which we use in conjunction with differential pulse-code modulation on spatially adjacent transformed subimage samples. For a set of thirty-three 64 × 64 images of eleven different categories, we compare the performancea of the discrete linear transform compression technique with the Karhunen-Loeve and Hadamard transform techniques. Our measure of performance is the mean-squared error between the original image and the reconstructed image. We multiply the mean-squared error with a factor indicating the degree to which the error is spatially correlated. We find that for low compression rates, the Karhunen-Loeve outperforms both the Hadamard and the discrete linear basis method. However, for high compression rates, the performance of the discrete transform method is very close to that of the Karhunen-Loeve transform. The discrete linear transform method performs much better than the Hadamard transform method for all compression rates.

Discrete cosine transform signal processor

Abstract: A processor for performing a discrete cosine transform of an input signal, suitable for real-time television image processing, specifically for obtaining an acceptable picture when the number of bits of information available for describing the picture and/or the channel bandwidth are severely limited, comprising: two complex read-only memories, an input and output read-only memory, each containing a predetermined number of data points arranged in a predetermined manner; two complex multipliers, an input and an output multiplier, each having an input from one of the read-only memories, an input which is connectable to the external signal of N data values which is to be transformed discretely and cosinusoidally; a complex transversal filter, having 2N-1 taps, the input to the filter being the output of the input multiplier; the output of the transform processor comprising the output of the output multiplier.

Image Transmission via Spread Spectrum Techniques

Abstract: : The report describes the progress on second phase of a program on image bandwidth reduction for application to the ARPA remotely piloted vehicle (RPV) problem of sending television images over spread spectrum channels The report details the first quarter of a hardware development and implementation phase Hardware was constructed to perform linear transformations on the television signal Both surface acoustic wave and charge transfer devices were built and tested It was decided to proceed with charge transfer devices for the final design The study of performance tradeoff as a function of block size and transform was continued It was determined that a Cosine transform together with a differential pulse code modulation (DPCM) transform in the second dimension offers near optimal performance A principal result of this quarter is the determination that the DPCM and Cosine mixed transform are an optimal performance system A second result is that charge transfer device hardware has been built which approximates the final prototy#e hardware