Method and system for bit-rate compression of digital data transmitted between a television transmitter and a television receiver
First Claim
1. A method of bit-rate compression of digital data transmitted between at least one television transmitter and a televison receiver, the data being representative of the values of luminance and/or of chrominance of each point of a television image and being coded at the transmitter by means of a differential coding device of the type comprising at least one predictor, at least one quantizer, a device for reconstruction of the transmitter data and a code allocator, said data being decoded at the receiver by a differential decoder comprising at least one code converter, a predictor and a device for reconstruction of the transmitted data, wherein said method comprises coding the data relating to each current point to be transmitted by means of a first predictor and a first quantizer when the point belongs to a contour area, coding the data relating to each point of a uniform or slightly textured area by means of at least a second predictor and a second quantizer, and decoding each received data code at the receiver by means by a prediction characteristic providing a prediction value which is identical with the value previously computed at the transmitter for decoding the received data code, in comparing the prediction errors of each predictior of the transmitter and of the receiver with at least one predetermined error threshold value in order to code the current point data at the transmitter by means of different code words of fixed length, depending on whether the results of comparisons of the errors of prediction of the points adjacent to the current point already transmitted to the receiver indicate that the point is in a contour area or in a uniform area and in order to switch the receiver to a predictor which has the same prediction dharacteristic as the predictor employed earlier for coding the current point data at the transmitter.
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Abstract
A method and the system for bit-rate compression of digital data between a television transmitter and receiver employs at the transmitter a differential coding device comprising a code allocator coupled respectively to the outputs of predictors which deliver the spatial prediction errors of the contour areas or highly textured areas of the image, the spatial prediction errors of the uniform areas and the temporal prediction errors of the uniform and fixed areas. The code allocator is controlled by a selecting device which selects one output of the predictors for applying a prediction error value to the input of a coding structure of the code allocator in order to code each datum of a current point applied to the input of a predictor in three different fixed-length codes, depending on whether the current point is located in a contour area or highly textured area of the image or whether the current point is located in a fixed or moving uniform area.
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Citations
10 Claims
- 1. A method of bit-rate compression of digital data transmitted between at least one television transmitter and a televison receiver, the data being representative of the values of luminance and/or of chrominance of each point of a television image and being coded at the transmitter by means of a differential coding device of the type comprising at least one predictor, at least one quantizer, a device for reconstruction of the transmitter data and a code allocator, said data being decoded at the receiver by a differential decoder comprising at least one code converter, a predictor and a device for reconstruction of the transmitted data, wherein said method comprises coding the data relating to each current point to be transmitted by means of a first predictor and a first quantizer when the point belongs to a contour area, coding the data relating to each point of a uniform or slightly textured area by means of at least a second predictor and a second quantizer, and decoding each received data code at the receiver by means by a prediction characteristic providing a prediction value which is identical with the value previously computed at the transmitter for decoding the received data code, in comparing the prediction errors of each predictior of the transmitter and of the receiver with at least one predetermined error threshold value in order to code the current point data at the transmitter by means of different code words of fixed length, depending on whether the results of comparisons of the errors of prediction of the points adjacent to the current point already transmitted to the receiver indicate that the point is in a contour area or in a uniform area and in order to switch the receiver to a predictor which has the same prediction dharacteristic as the predictor employed earlier for coding the current point data at the transmitter.
- 7. A system for bit-rate compression of digital data transmitted between at least one television transmitter and a television receiver in which the data are representative of values of luminance and/or chrominance of each point of a television image and are coded at the transmitter by a differential coding device of the type comprising at least one predictor, at least one quantizer, a device for reconstruction of the transmitted data and a code allocator, and are decoded at the receiver by a differential decoder comprising at least one code converter, a predictor and a device for reconstruction of the transmitted data, the data relating to each current point to be transmitted being coded by means of a first predictor and a first quantizer when the point belongs to a contour area, the data relating to each point of a uniform area or slightly textured area being coded by means of at least a second predictor and a second quantizer and being decoded at the receiver by means of a prediction characteristic providing a prediction value which is identical with the value previously computed at the transmitter for decoding the code of the received data, said device for differential coding of the transmitter comprising a code allocator coupled respectively to the outputs of first, second and third devices for computing prediction errors which compute respectively the spatial prediction errors of the contour areas or highly textured areas of the image, the spatial prediction errors of the uniform areas and the temporal prediction errors of the uniform and fixed areas, the code allocator being controlled by a selecting device which selects one output of the first, second and third devices for computing prediction errors in order to apply a prediction error value to the input of a coding structure of the code allocator in order to code each current point data applied to the input of a predictor in three different fixed-length codes depending on whether the current point is located in a contour area or highly textured area of the image or whether the current point is located in a uniform area which is fixed or in motion.
Specification