Showing papers on "Encoder published in 1987"

Oversampled Sigma-Delta Modulation

Abstract: Oversampled sigma-delta modulation has been proposed as a practical implementation for high rate analog-to-digital conversion because of its simplicity and its robustness against circuit imperfections. To date, mathematical developments of the basic properties of such systems have been based either on simplified continuous-time approximate models or on linearized discrete-time models where the quantizer is replaced by an additive white uniform noise source. In this paper, we rigorously derive several basic properties of a simple discrete-time single integrator loop sigma-delta modulator with an accumulate-and-dump demodulator. The derivation does not require any assumptions on the correlation or distribution of the quantizer error, and hence involves no linearization of the nonlinear system, but it does show that when the input is constant, the state sequence of the integrator in the encoder loop can be modeled exactly as a linear system in an appropriate space. Two basic properties are developed: 1) the behavior of the sigma-delta quantizer when driven by a constant input and its relation to uniform quantization, and 2) the rate-distortion tradeoffs between the oversampling ratio and the average mean-squared quantization error.

Optimal quantizer design for noisy channels: An approach to combined source - channel coding

Abstract: We present an analysis of the zero-memory quantization of memoryless sources when the quantizer output is to be encoded and transmitted across a noisy channel. Necessary conditions for the joint optimization of the quantizer and the encoder/decoder pair are presented, and an iterative algorithm for obtaining a locally optimum system is developed. The performance of this locally optimal system, obtained for the class of generalized Gaussian distributions and the binary symmetric channel, is compared against the optimum performance theoretically attainable (using rate-distortion theoretic arguments), as well as against the performance of Lloyd-Max quantizers encoded using the natural binary code and the folded binary code. It is shown that this optimal design could result in substantial performance improvements. The performance improvements are more noticeable at high bit rates and for broad-tailed densities.

Encoding of correlated observations

Abstract: An important class of engineering problems involves sensing an environment and making estimates based on the phenomena sensed. In the traditional model of this problem, the sensors' observations are available to the estimator without alteration. There is .growing interest in {\em distributed} sensing systems in which several observations are communicated to the estimator over channels of limited capacity. The observations must be separately encoded so that the target can be estimated with minimum distortion. Two questions are addressed for a special case of this problem wherein there are two sensors which observe noisy data and communicate with a single estimator: 1) if the encoder is unlimited in complexity, what communication rates and distortions can be achieved, 2) if the encoder must be a quantizer (a mapping of a single observation sample into a digital output), how can it be designed for good performance? The first question is treated by the techniques of information theory. It is proved that a given combination of rates and distortion is achievable if there exist degraded versions of the observations that satisfy certain formulas. The second question is treated by two approaches. In the first, the outputs of the quantizers undergo a second stage of encoding which exploits their correlation to reduce the output rate. Algorithms which design the second stage are presented and tested. The second approach is based on the {\em distributional distance}, a measure of dissimilarity between two probability distributions. An algorithm to modify a quantizer for increased distributional distance is derived and tested.

Stem for dynamically compressing and decompressing electronic data

Abstract: A data compression system for encoding and decoding textual data, including an encoder for encoding the data and for a decoder for decoding the encoded data Both encoder and decoder have dictionaries for storing frequently-appearing strings of characters Each string is identified by a unique pointer The input data stream is parsed and matched with strings in the encoder dictionary using a novel matching algorithm The pointer associated with the matched string is then transmitted to a remote location for storage or decoding Thereafter, using a novel update algorithm the encoder dictionary is updated to include new strings of data based on the matched string of data If required, a novel deletion algorithm is employed to remove infrequently used strings of data to provide room for the newly generated strings of data The strings of data may be arranged using a modified least recently used queue The decoder matches each unique pointer in the stream of compressed input data with a corresponding pointer in the decoder dictionary The decoder then transmits the string of character data associated with the matched pointer, thereby providing textual data in original, uncompressed form Thereafter, using the novel update and deletion algorithms, new strings of data are added to, and old strings of data are deleted from, the decoder dictionary, so as to ensure both encoder and decoder dictionaries contain identical strings of data

Temperature-sensing system for cattle

Abstract: Disclosed is a device for detecting temperatures which differ from a variable norm of particular use in detecting elevated temperatures in cattle. The device, one being attached to each animal, includes a square wave generator, an identification number encoder for outputting the identification number of the particular animal in the herd, a fever detector with an ambient temperature compensating circuit which provides output only when internal temperature of the animal is above a preset value for a given ambient temperature, and a transmitter which sends the identification code to a receiver. In certain embodiments, no separate fever detector is provided; rather the square wave generator outputs a frequency-modulated signal related to the internal body temperature. Of particular interest is the identification number encoder which intermittently outputs a preset hardwired identification code to the transmitter at periodic intervals for transmission to a receiver either at constant intervals or when temperatures sensed by a temperature detector exceed the variable norm by a preset given amount.

Multiple display system

Abstract: A multiple display system is adapted to display data in the VIDEOTEX standard on a display formed of a plurality of display devices. The system comprises an encoder (l,2) for generating a code on the basis of internal or external data supplied thereto, a plurality of decoders (3A to 3I), each of which includes a central processing unit, successively arranged in series with respect to the encoder, and a plurality of display devices (4A to 4I) provided respectively corresponding to the plurality of decoders to thereby display a large image by the plurality of display devices. The encoder inserts an identification number in a predetermined portion of a data sequence. The plurality of decoders respectively select data with corresponding identification number, convert the selected data into a video signal, and supply respective display devices with the video signal.

Encoder capable of faithfully and adaptively encoding a moving image

Abstract: In an encoder responsive to a sequence of coefficient blocks each of which is composed of a plurality of orthogonal transform coefficients subjected to predictive encoding and orthogonal transform, the coefficient blocks are classified by a classification circuit (55) into a plurality of classes to produce a control signal (CONT) representative of the classes. A quantization unit (60), a code conversion unit (61), and a coefficient selection unit (62, 64) are controlled by the control signal to select quantization characteristics, code conversion characteristics, and coefficient selection characteristics. The quantization unit comprises a plurality of quantizers corresponding to the quantization characteristics while the code conversion unit and the coefficient selection unit comprise a plurality of code converters and a plurality of selection tables corresponding to the code conversion characteristics and the coefficient selection characteristics, respectively. Consequently, the coefficients are adaptively encoded into a reduced amount of encoded codes on encoding a moving image.

Adaptive graylevel image compression system

Abstract: Apparatus and method for modelling differential pulse code modulation (DPCM) input data for entropy coding. In partic­ular, the sign and magnitude of one piece of DPCM data after another are modelled to provide a magnitude state input and a sign state input to provide context for DPCM magnitude in­put and DPCM sign input, respectively, to an entropy encoder or decoder. That is, the DPCM magnitudes of earlier pieces of (context) DPCM magnitude data are re-mapped for each such earlier piece of data, the re-mapped data being aggregated to form a combined value indicative of the magnitude state input. Similarly, the DPCM signs of earlier pieces of (con­text) DPCM sign data are re-mapped for each such earlier piece of data, the re-mapped data being aggregated to form a combined value indicative of the sign state input. In an image data compression system, the magnitude state input serves as an activity indicator for picture elements (pixels) neighboring a "subject" pixel. According to the invention, the DPCM signal is derived from a difference value calculated by subtracting one of a plurality of predictor values from the graylevel value X of the subject pixel. The selection of predictor value P is based on the value of the magnitude state (activity indicator). In addition, the difference value is subject to adaptive quantization in which one of a plu­rality of quantizers is employed in assigning the (X-P) dif­ference value to a quantization level. The selection of quantizers is also based on the value of the magnitude state (activity indicator).

Arithmetic coding for data compression/de-compression by selectively employed, diverse arithmetic coding encoders and decoders

Abstract: A data compression/de-compression system includes a first arithmetic coding encoder, characterized by a first set of encoding conventions, which encoder generates a code stream that points to an interval along a number line in response to decision event inputs. The code stream can be adjusted to point to the same interval as code streams generated by one or more other arithmetic coding encoders characterized by encoding conventions differing in some way from those in the first set. In a binary context, optimal hardware encoders increment or decrement the value of the code stream in response to each occurrence of a more probable decision event while optimal software so changes the code stream value for each occurrence of a less likely event. According to the invention, the code streams for optimal hardware encoders and optimal software encoders are made either identical or compatible to enable similar decoding for each. Identical or compatible code streams are obtained from encoders having different event sequence or symbol ordering along intervals on the number line. Moreover, various hardware and software decoders--with respective symbol ordering and other conventions--can be used in conjunction with encoders having respective conventions, wherein each decoder retrieves the same sequence of decisions for a code stream pointing to a given interval. In both encoding and decoding, the present invention overcomes finite precision problems of carry propagation and borrow propagation by handling data in bytes and bit stuffing at byte boundaries and by pre-borrowing as required.

Gain-Adaptive Vector Quantization with Application to Speech Coding

Abstract: The generalization of gain adaptation to vector quantization (VQ) is explored in this paper and a comprehensive examination of alternative techniques is presented. We introduce a class of adaptive vector quantizers that can dynamically adjust the "gain" or amplitude scale of code vectors according to the input signal level. The encoder uses a gain estimator to determine a suitable normalization of each input vector prior to VQ encoding. The normalized vectors have reduced dynamic range and can then be more efficiently coded. At the receiver, the VQ decoder output is multiplied by the estimated gain. Both forward and backward adaptation are considered and several different gain estimators are compared and evaluated. Gain-adaptive VQ can be used alone for "vector PCM" coding (i.e., direct waveform VQ) or as a building block in other vector coding schemes. The design algorithm for generating the appropriate gain-normalized VQ codebook is introduced. When applied to speech coding, gain-adaptive VQ achieves significant performance improvement over fixed VQ with a negligible increase in complexity.

A New Error Control Scheme for Hybrid ARQ Systems

Abstract: This paper introduces the concept of a generalized hybrid ARQ (GH-ARQ) scheme for adaptive error control in digital communication systems. This technique utilizes the redundant information available upon successive retransmissions in an efficient manner so as to provide high throughput during poor channel conditions. A new class of linear codes is proposed for the GH-ARQ system application. The main feature of this class of codes is that the encoder/decoder configuration does not change as the length of the code is varied. As a result, the receiver uses the same decoder for decoding the received information after every retransmission while the error correcting capability of the code increases, thereby leading to an improved performance and minimum complexity for the overall system implementation.

Features of a magnetic rotary encoder

Abstract: A magnetic rotary encoder has several features different from those of an optical one : simple structure, quick response, good resistance to humid and dirty environments, easiness to get multi-functions and small power dissipation. According to those features, magnetic encoders are expected to be widely used.

Device for the remote control of a videorecorder or a videoreceiver

Abstract: A conventional video recorder (20) comprises electromechanical components, electronic circuits and a control unit with which there are associated both front panel controls and a user remote control unit with a sensor to which signals can be sent from a hand-held remote control unit (24). In addition to these conventional features an off-air remote controller (30) is provided. This is capable of decoding control signals associated with the television signal and includes an encoder which generates outputs which match those from the conventional user remote control unit (24).

Electric shift apparatus

Abstract: An electric shift apparatus for use with a motor vehicle having an automatic transmission. The apparatus includes a power module adapted to be mounted on the housing of the transmission proximate the transmission mode select lever and the transmission kick-down lever and a control module adapted to be mounted in the passenger compartment of the vehicle. The power module includes an electric motor assembly drivingly connected to the free end of the mode select lever and a solenoid drivingly connected to the free end of the kick-down lever. The control module includes a plurality of push button members corresponding respectively to the transmission shift positions. An encoder device carried by the motor assembly of the power module provides a constant coded signal indicating the instantaneous position of the transmission mode select lever and this coded signal is compared by comparator means in the logic of the control unit with the selected shift position. The comparator means generates a signal to the motor assembly to move the mode select lever in a direction to achieve the selected shift position and stops the motor assembly when the encoder signal received from the power module matches the selected shift position indicating that the selected shift position has been achieved.

Compact plotter for generation of accurate plotted images of long length

Abstract: A compact plotter is disclosed, having a small area in which a plurality of print heads (10) are laterally scanned to print impressions on the paper (14), and the paper (14) is incrementally advanced by an indexer (42) past the print heads (10) A paper travel encoder (36) measures the paper advancement A computer 22 and a processor 26 are provided to coordinate the printing of pattern data stored in a data base (24) both with the movement of the print heads (10) and the advancement of the paper (14) The computer (22) allocates data from the data base (24) to be printed according to the amount of paper advancement If the paper (14) is advanced more than a predefined amount, more data is allocated for printing than is actually printed If the paper (14) is advanced less than the predefined amount, less data is allocated to be printed than is actually printed

System for formatting digital signals to be transmitted

Abstract: In a preferred embodiment, a computer is employed to control the system. The system initially accepts analog signals and converts them into digital signals, which are then compressed, at a DPCM encoder, into a three bit code. Thereafter the once compressed signals are further compressed in accordance with a variable length code. The twice compressed digital signals are transmitted through formatter circuitry whereat a tag is added to indicate (in addition to other information) what forms of compression have been employed on the digital signals which follow the tag. The twice compressed and tagged digital signals are forwarded to a buffer storage device. The role of the buffer storage is to keep a relatively constant supply of data signals so that there is a relatively constant supply of pels moving to the transmitter at a constant frequency. The computer monitors the buffer fullness and the rate at which it is being loaded or is emptying. In response to such monitoring the system compresses more lines of digitized video or compresses less lines of digitized video. Additional compression can be effected by horizontal subsampling or by changing the first DPCM coding operation from a three bit code to a two bit code. The present system also includes a decoding loop which accepts the compressed and tagged digital signals. The compressed signals are initially synchronized in response to the tags so that the compressed signals are properly advanced into the stages of the decoding loop. The compressed signals are then decompressed (decoded) in accordance with the information carried by the tag. Thereafter the expanded digital signals are converted into analog signals for display on a video screen.

Code excited linear predictive vocoder

Abstract: Apparatus for encoding speech using a code excited linear predictive (CELP) encoder using a recursive computational unit. In response to a target excitation vector that models a present frame of speech, the computational unit utilizes a finite impulse response linear predictive coding (LPC) filter and an overlapping codebook to determine a candidate excitation vector from the codebook that matches the target excitation vector after searching the entire codebook for the best match. For each candidate excitation vector accessed from the overlapping codebook, only one sample of the accessed vector and one sample of the previously accessed vector must have arithmetic operations performed on them to evaluate the new vector rather than all of the samples as is normal for CELP methods. For increased performance, a stochastically excited linear predictive (SELP) encoder is used in series with the adaptive CELP encoder. The SELP encoder is responsive to the difference between the target excitation vector and the best matched candidate excitation vector to search its own overlapping codebook in a recursive manner to determine a candidate excitation vector that provides the best match. Both of the best matched candidate vectors are used in speech synthesis.

Single channel encoder system

Abstract: A control system providing a control of position, velocity, and direction of movement of a member in an axis of freedom which employs a scale having scale divisions thereon and bands or zones defining limits of constant velocity control, acceleration and deceleration zone limits, and a rest or parking position. The scale spans and parallels the axis of freedom. A single channel transducer or encoder mounted on and moving with the member produces time varying output signals in response to the sensing of scale divisions along the scale and signals of different characteristic in response to encoder sensing of the limit bands. The time varying output signals are employed as scale division count signals for position determination and as scale division count signals per unit of time, for velocity feedback. The signals of different characteristic produced upon entering and during crossing of the limit bands, are utilized in a system of logic for computing control system signals to compensate control uncertainties in differing functional modes of the control system.

Code converter for data compression/decompression

Abstract: A code converter has a network of logic circuits connected in reverse binary tree fashion with logic paths between leaf nodes and a common root node. Characters are compressed from standard codes to variable-length Huffman code by pulse applying connections to the paths from a decoder. An OR-gate is connected to "1" branches of the network to deliver the output code. Characters are decompressed from Huffman to standard codes by connection of the Huffman code to control the clocked logic circuits to deliver a pulse from the root node to one of the inputs of an encoder. A feedback loop connects the root node and the path end nodes to initiate the next conversion. Alternative embodiments have decoder staging to minimize delay and parallel compressed code output.

Very low rate speech encoder and decoder

Abstract: A speech encoder is disclosed quantizing speech information with respect to energy, voicing and pitch parameters to provide a fixed number of bits per block of frames. Coding of the parameters takes place for each N frames, which comprise a block, irrespective of phonemic boundaries. Certain frames of speech information are discarded during transmission, if such information is substantially duplicated in an adjacent frame. A very low data rate transmission system is thus provided which exhibits a high degree of fidelity and throughput.

Image data processing apparatus capable of high-speed data encoding and/or decoding

Abstract: An image data processing apparatus capable of high-speed encoding even for intermittently supplied image data is provided with a memory storing image data, an encoder for encoding the image data and/or a decoder for decoding such encoded information and a transfer unit for DMA transfer of the image data from the memory to the encoder. A supply may be provided for supplying the encoder with the reference signals in synchronization with the DMA transfer of the image data by the transfer unit. The encoding and/or decoding are performed intermittently, e.g., in response to supply of the reference signals.

Forward error correction system

Abstract: The system first incorporates an encoder which utilizes a 1/2 rate convolutional encoder to encode the data and a supplementary coding system for converting the 1/2 rate coded data to a nominal 3/4 rate. Thereafter, in order that the encoded data fits within the fixed frame length which has been adopted as a standard for the present TDMA transmission system, a portion of the excess data in each frame of encoded data put out by the encoder must be deleted or punched out. These bits are spaced throughout the frame to minimize the effect of the punchout routine. On the decoding side of the system, bits must be reinserted in the same place where they were deleted in the encoder. Because these bits were removed at the encoder, the decoder cannot possibly know what they were. It is not important to know what they were, but rather when in the received bit stream they would have occurred. In these places, place holding bits that are marked as such are inserted. This function is achieved by arbitrarily inserting either 1's or 0's in the bit stream, and providing an accompanying bit stream which incorporates flag bits for marking the existence of these place holding bits. Later processing in the decoder then simply treats these bits as place holders. That is, they do not add information that can help correct errors, nor do they cause errors.

Shared circuitry for the encoding and syndrome generation functions of a Reed-Solomon code

Abstract: Apparatus is disclosed for providing an improved encoder and frequency-domain syndrome generator circuit implementing Reed-Solomon codes which reduces hardware by sharing circuitry between the encoding and frequency-domain syndrome generation functions. Self-checking for proper encoder operation during write operations is achieved by verifying that all remainders from dividing codewords by factors of the code generator polynomial are equal to zero after encoding. Apparatus implements fast finite-field multiplication by a selected constant using Read Only Memory circuits. Hardware required is further reduced by incorporating Random Access Memory circuits and employing time-multiplexing techniques. Interleaved codewords are supported by implementing memory circuits for storing intermediate results of other codewords while processing symbols from one codeword.

Digital transmission system

Abstract: The present invention relates to a digital transmission system provided with a transmitter 11 and a receiver 12, wherein the transmitter 11 comprises a first clock extracting device 13, 14 for detecting a synchronizing signal contained in a first digital audio interface (DAI) format signal from the receiver 12 and generating a first clock signal of a predetermined frequency in being phase-locked with the synchronizing signal, a data read-out device 4 for reading out data from a recording medium on the basis of the first clock signal, and a first encoder 5 for encoding the data from the data read-out device 4 in a second digital audio interface (DAI) format signal on the basis of the first clock signal, while the receiver 12 comprises second clock extracting device 6, 7 for detecting a synchronizing signal contained in the second DAI format signal and generating a second clock signal of a predetermined frequency in being phase-locked with the synchronizing signal, a decoder 8 for decoding data from the second DAI format signal on the basis of the second clock signal, an oscillator 3 for generating a master clock, D/A a converter 9 for digital-to-analog converting the decoded data on the basis of the master clock, and a second encoder 15 for encoding the master clock to derive the first DAI format signal, whereby the system is synchronously operated by the master clock in a manner that digital-to-analog conversion can be effected with a timing clock signal which is not mixed with jitter.

Interactive audio teaching aid

Abstract: An interactive compact disc system (10) having a teaching mode in addition to an entertainment mode is provided for the recovery of a predetermined aural response from predetermined randomly accessed storage on a compact digital disc. The interactive compact disc system (10) includes a mode select switch interface (26) which is coupled to microprocessor (22) by data bus (34) and address bus (32) for selecting the desired operational node. A keyboard (12) which includes a removable graphic overlay, provided for use in the teaching mode, is coupled to keyboard decoder/driver (14). Keyboard decoder/driver (14) generates a unique character code for each of the keyboard switches in keyboard (12). Microprocessor (22) uses that unique character code to generate an address for accessing the track encoder read only memory (24). Track encoder read only memory (24) provides a lock-up table which in effect cross references each keyboard key switch with a discrete audio segment on a compact digital disc located in disc playback unit (30).

A time-clustered cardio-respiratory encoder and method for clustering cardio-respiratory signals

Abstract: The invention pertains to a method and its implementation in an encoder for retrospectively cluste­ring NMR k-space measurement profiles in the cardiac phase respiratory phase plane, which method and encoder function to: 1) reduce cardio-vascular and respiratory flow motion image artifacts, and 2) to characterized quantita­tively cardiac structure/function both with and without imaging.

Highly reliable multilevel channel coding system using binary convolutional codes

Abstract: A multilevel channel coding system using binary convolutional codes is proposed. This system achieves high coding gain. For example, we can obtain an 8-PSK system with rate R = 2/3, which has 6.02 dB coding gain over uncoded 4-PSK and is implemented as easily as Ungerboeck's system with total encoder memory K = 4.

Data structure of Huffman codes and its application to efficient encoding and decoding (Corresp.)

Abstract: The data structure of Huffman codes and its application to efficient encoding and decoding of Huffman codes are studied in detail. The tree structure is presented by a two-dimensional array which can be applied for the decoding of Huffman codes as a state transition table of the finite-state decoding automaton. Inversion produces a one-dimensional state transition table of the semiautonomous finite-state sequential machine which can be used as a Huffman encoder with a push-down stack. The encoding and decoding procedures are simple and efficient. It is not only possible to implement by simple hardware but is also applicable to software implementation.

Velocity Observations From Discrete Position Encoders

Abstract: A discrete position encoder is an inexpensive means for sensing the angular position of a rotating device. Often a system with higher performance can be achieved if the angular velocity is known in addition to the position. Typically, the output of a discrete position encoder is two square wave signals in quadrature. This paper investigates various methods for processing these signals to observe the velocity in real time. High performance observers based on Taylor series expansions, backward difference expansions, and least square curve fits are developed. The accuracy of the different observers are analyzed by simulations for systems with time measurement truncation and imperfect encoders. The least square curve fit based observers are the most tolerant observers investigated due to the inherent low pass filtering.

Self-gapping optical encoder

Abstract: A modular optical encoder (1) includes a housing (23), a rotatable cam-loaded cover (21), an emitter/detector module (15) and a code wheel (17) which is positionable upon the shaft (5) of a motor. The code wheel (17) is positioned automatically against the cover (21) during attachment of the encoder (1) to the motor to set the desired emitter and detector gaps. Once the code wheel (17) is locked to the shaft (5), the cover (21) may be rotated to disengage the cams (47) and followers (43) so that the code wheel (17) is free to turn with the motor shaft (5).