Showing papers on "Discrete cosine transform published in 1977"

A Fast Computational Algorithm for the Discrete Cosine Transform

Abstract: A Fast Discrete Cosine Transform algorithm has been developed which provides a factor of six improvement in computational complexity when compared to conventional Discrete Cosine Transform algorithms using the Fast Fourier Transform. The algorithm is derived in the form of matrices and illustrated by a signal-flow graph, which may be readily translated to hardware or software implementations.

Adaptive Coding of Monochrome and Color Images

Abstract: An efficient adaptive encoding technique using a new implementation of the Fast Discrete Cosine Transform (FDCT) for bandwidth compression of monochrome and color images is described. Practical system application is attained by maintaining a balance between complexity of implementation and performance. FDCT sub-blocks are sorted into four classes according to level of image activity, measured by the total ac energy within each sub-block. Adaptivity is provided by distributing bits between classes, favoring higher levels of activity over lower levels. Excellent performance is demonstrated in terms of mean square error and direct comparison of original and reconstructed images. Results are presented for both noiseless and noisy transmission at a total rate of 1 bit and 0.5 bit per pixel for a monochrome image and for a total rate of 2 bits and 1 bit per pixel for a color image. In every case the total bit rate includes all overhead required for image reconstruction and bit protection.

Adaptive transform coding of speech signals

Abstract: This paper discusses speech coding systems based upon transform coding (TC). It compares several transforms and shows that the cosine transform leads to a nearly optimum performance for almost all speech sounds. Various adaptive coding strategies are then investigated, and a coding scheme is proposed that is based on a nonadaptive discrete cosine transform (DCT), on an adaptive bit assignment, and on adaptive quantization. The adaptation is controlled by a short-term basis spectrum that is derived from the transform coefficients prior to coding and transmission and that is transmitted as side information to the receiver. The main result is that this adaptive transform coder performs better than all known nonpitch-tracking coding schemes; it extends the range of speech waveform coding to lower bit rates and closes the gap between vocoders and predictive waveform coders.

Interframe Cosine Transform Image Coding

Abstract: Two-dimensional transform coding and hybrid transform/DPCM coding techniques have been investigated extensively for image coding. This paper presents a theoretical and experimental extension of these techniques to the coding of sequences of correlated image frames. Two coding methods are analyzed: three-dimensional cosine transform coding, and two-dimensional cosine transform coding within an image frame combined with DPCM coding between frames. Theoretical performance estimates are developed for the coding of Markovian image sources. Simulation results are presented for transmission over error-free and binary symmetric channels.

Coding isotropic images

Abstract: Rate-distortion functions for 2-dimensional homogeneous isotropic images are compared with the performance of five source encoders designed for such images. Both unweighted and frequency weighted mean-square error distortion measures are considered. The coders considered are a) differential pulse code modulation (DPCM) using six previous samples or picture elements (pels) in the prediction--herein called 6-pel DPCM, b) simple DPCM using single-sample prediction, c) 6-pel DPCM followed by entropy coding, d) 8 \times 8 discrete cosine transform coding, and e) 4 \times 4 Hadamard transform coding. Other transform coders were studied and found to have about the same performance as the two transform coders above. With the mean-square error distortion measure, 6-pel DPCM with entropy coding performed best. Next best was the 8 \times 8 discrete cosine transform coder and the 6-pel DPCM--these two had approximately the same distortion. Next were the 4 \times 4 Hadamard and simple DPCM, in that order. The relative performance of the coders changed slightly when the distortion measure was frequency weighted mean-square error. From R = 1 to 3 bits/pel, which was the range studied here, the performances of all the coders were separated by only about 4 dB.

Side fringing fields and write and read crosstalk of narrow magnetic recording heads

Abstract: In magnetic recording systems the side fringing fields of magnetic recording heads are responsible for crosstalk from adjacent tracks and eventually for partial erasure of adjacent tracks, thereby limiting the attainable track density In this paper we derive analytical expressions for the magnetic field near the side of a recording head and calculate the cosine transform of the longitudinal field component, with the head side angle and gap length as parameters The field of a head of zero width is also considered Due to the side fringing field the written track is somewhat wider than the geometrical head width; the increase in width being approximately proportional to the maximum field strength in the recording medium and the head-to-medium distance The amplitude u of the read crosstalk signal from an adjacent, infinitesimally narrow track is calculated and it appears that it can be approximated by u/u_{0} = 05 \exp (-2\pi x/\lambda) , where u 0 is the on-track signal (with zero head-to-medium spacing), x is the distance between track and head side, and λ is the wavelength Maximum track densities are calculated for a specified crosstalk-to-signal ratio and a given head width and wavelength For a wavelength of 10 μm, a head width of 5 μm, and a crosstalk of -20 dB, the track density is limited to about 130 tracks/mm, assuming a track width equal to the head width When the track is taken to be 5 μm wider than the head to account for the effects of the write process, no guardband at all is needed for -20 dB crosstalk and the limit to the track density is 100 tracks/mn

On Interframe Transform Coding

Abstract: This paper is concerned with interframe coding of monochrome pictures using 3-dimensional transforms First, an algorithm which enables the vector processing of 3-dimensional arrays is derived Next, this algorithm is used in an interframe transform coding experiment Picture data (6 bits/pel) is processed in ( 4 \times 4 \times 4 ) blocks using the Walsh-Hadamard transform (WHT), and the discrete cosine transform (DCT) The corresponding reconstructed pictures (1 bit/pel) are included

Linear Signal Processing Architectures

Abstract: A large portion of the computational load for many signal processing problems consists of the computation of linear transforms. For time-invariant linear transforms such as cross convolution or matched filtering, the transversal filter provides a highly parallel computational module with high throughput and minimal control overhead. This paper will show how similar computational modules can be configured to provide similar computational advantages for a large class of timevariant linear transforms including one-dimensional and multi-dimensional discrete Fourier transforms and one-dimensional and two-dimensional discrete cosine transforms. Furthermore, time-variant transform modules may be combined to implement high capacity time-invariant linear transforms. The implementation of these techniques using surface acoustic wave (SAW) and charge coupled device (CCD) technology permits the real-time solution of several important signal processing problems including image data compression, spectrum analysis, convolutional array scanning and beamforming. Advanced digital and integrated analog/digital architectures will permit these fast processing techniques to be extended to high accuracy and adaptive processing tasks.

Adaptive coding of monochrome and color images

Abstract: An efficient adaptive encoding technique using a new implementation of the Fast Discrete Cosine Transform (FDCT) for bandwidth compression of monochrome and color images is described. Practical system application is attained by maintaining a balance between complexity of implementation and performance. FDCT sub-blocks are sorted into four classes according to level of image activity, measured by the total ac energy within each sub-block. Adaptivity is provided by distributing bits between classes, favoring higher levels of activity over lower levels. Excellent performance is demonstrated in terms of mean square error and direct comparison of original and reconstructed images. Results are presented for both noiseless and noisy transmission at a total rate of 1 bit and 0.5 bit per pixel for a monochrome image and for a total rate of 2 bits and 1 bit per pixel for a color image. In every case the total bit rate includes all overhead required for image reconstruction and bit protection.

Convergence of certain cosine sums in the metric space l

Abstract: We consider here the Ll convergence of Rees-Stanojevic cosine sums to a cosine trigonometric series belonging to the class S defined by Sidon and deduce as corollaries some previously known results from our result.

Fast two dimensional fourier transform device

Abstract: Two dimensional optical or electrical images are processed through a storage tube designed to yield the correlation function between the input images and stored images. By generating a series of stored images representing sine and cosine components of the Fourier transform, a fast, two-dimensional transform of the image is obtained.

Digital Hardware for Sine-Cosine Function

Abstract: The design of a high-speed digital processor for the sine and cosine functions is discussed. The hardware provides a significant speed advantage over software calculations of these functions. The special processor provides floating point results of 35 bit accuracy within 40 μs after the argument is loaded. This is faster by a factor of 5 over the minicomputer software formerly used. The hardware has the further feature that both the sine and the cosine of the argument are calculated simultaneously.

Microprocessor System For TV Imagery Compression

Abstract: Applying a new algorithm for the Discrete Cosine Transform superior to any published to date, it is shown that an off-the-shelf microprocessor chip, the Am 2901 4-bit bipolar slice, can be employed in a 12-bit configuration to perform TV imagery data compression in real time. The method of compression is the hybrid technique due to Habibi -- DCT along a 32-pixel segment of a TV line and Differential Pulse Code Modulation line to line, thus processing only one eighth of each field at one time. The significance of the new algo-rithm is that it permits an all-digital implementation of a TV data compression system for Remotely Piloted Vehicles and spacecraft using "off-the-shelf" circuitry.© (1977) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A comparison of the visual effects of two transform domain encoding approaches

Abstract: Rate-distortion theory using the mean squared error criterion is often used to design digital image coding rules. The resulting distortion is, in theory, statistically equivalent to omitting components of the image from transmission. We compare a rate-distortion simulation using the discrete cosine transform to a method which is statistically equivalent to adding uncorrelated random noise to the image. This latter method is based on a PN (pseudo-noise) transform, which is generated from a Hadamard matrix whose core consists of the cyclic shifts of a binary maximum length linear shift register sequence. Visual comparisons of the two approaches are made at the same mean squared error. In all cases, the images encoded using the PN transform method showed superior definition of detail and less geometrical distortion at transform block boundaries than the images encoded using the discrete cosine method. The results of this experiment suggest that image appearance may be improved by designing transform coefficient quantization rules to approximate the effects of additive noise rather than to omit low energy image components, as dictated by conventional rate-distortion theory.© (1977) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Book reviews - Orthogonal transforms for digital signal processing

Abstract: digital and digital-to-analog conversion techniques and the circuitry for implementation are explored in Chapter 14. The concluding chapter of the book presents various timing circuits for monostable and astable multivibrators. Timing circuit operation is illustrated for CMOS, ECL, and TZL gates, and for use with the 555 timer. In evaluating this bo.ok a s a course textbook or for self study, this reviewer gives it very high marks. The explanations are clear and well illustrated with example calculations and problems. There are more than 400 homework problems provided, and a solution manual and an answer book are also available to instructors. Also, the authors state in the Preface that they"wil1 be happy to furnish a set of laboratory experiments currently used at CCNY (City College of the City University of New York) in conjunction with this text." In summary, the combination of'the topical content and the clarity of explanation in this book when mixed with proven technical writing successes of the authors over the last 30 years assures this reviewer that this volume will become a well-recognized text for practical engineering in digital integrated electronics.