Showing papers on "Hadamard code published in 1973"

Intraframe Image Coding by Cascaded Hadamard Transforms

Abstract: Various image coding schemes have been studied for digital transmission of videophone signals. The Hadamard transform, which is now studied for the transmission of pictures such as those from satellites, has been considered too complicated for public use, though the characteristics such as the ratio of bit-rate reduction are more desirable than those of differential pulse-code modulation (DPCM). We have found a very simple scheme of the transform, where digitized videophone signals are transformed to Hadamard components all digitally just by n digital adders and some shift registers for 2nth-order transform. For example, three adders are necessary for eighth-order transform. It is extendable to two-dimensional transform with ease. We have made an experimental model running in real time. Experiments and theoretical calculation have shown that 3 bits/sample are required for good picture quality in the case of two-dimensional (4 \times 2) th transform and 0.5 bits more for one-dimensional eighthorder transform.

Fast Hadamard Transform Using the H Diagram

Abstract: For the Hadamard matrix, a modified factorization procedure is developed that is likely as economical in storage requirements and in the number of computational operations as the conventional fast Hadamard transform. Using this specific factoring method, the procedure for obtaining the fast Hadamard transform may be interpreted as operations on an H diagram. The H diagram was originally derived by Marihugh and Anderson [1] to provide a graphical representation for logic functions.

Generator of pulse trains corresponding to walsh functions

Abstract: To generate pulse trains corresponding to the binary representation of numbers in the so-called Walsh code, the numbers ranging from 1 to m-1 where m 2k 1, a logic network RC1 with k+1 inputs and m outputs converts a selected binary number into the equivalent Walsh function whose bits are stored on associate flip-flops 501 - 516 forming respective stages of a dynamic memory. Another logic network RC2 determines the highestranking finite bit (1) of the selected binary number and, according to the rank thereof, selects one of k+1 subharmonically related pulse frequencies in the output of a frequency divider to step the dynamic memory at a cadence corresponding to that rank and to read out in series the contents of a corresponding number of pairs of memory stages, representing the stored Walsh function, the read-out recurring continuously until the next selection as the stored bits are recirculated in the memory 501 516.