Method and apparatus for filtering and coding images based on characteristics of an input image signal
First Claim
1. An interframe coding system for frame-to-frame coding of an input signal, comprising:
- a subtractor having inputs to receive the input signal and a predictive signal and an output to provide a predictive error signal corresponding to a difference between the input signal and the predictive signal;
an encoder having an input coupled to the output of the subtractor to receive the predictive error signal, having an output that provides a coded predictive error signal, and having a control input that receives a coding control signal for controlling a quantization step size of the encoder;
decoding means for producing a decoded signal having an input coupled to the output of the encoder to receive the coded predictive error signal, having an input to receive the predictive signal, and having an output that provides the decoded signal;
a frame memory having an input that receives the decoded signal and having an output that provides the predictive signal;
a controller having inputs that receive the input signal and the predictive signal, that calculates a difference between the input signal and the predictive signal and generates the coding control signal based on the difference, and having an output coupled to the control input of the encoder that provides the coding control signal for controlling the encoder.
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Abstract
An interframe coding system which eliminates higher frequency components contained in an image signal effectively and adaptively with an adaptive filter provided in a coding loop. The adaptive filter eliminates the higher frequency components with the optimal filtering intensity for an image signal specified with a filtering coefficient which is decided by a filter controller. The filtering coefficient is decided by normalization of the difference between an input image signal and a predictive signal from a frame memory by the "Activity" of the input image signal or the predictive signal. The "Activity" can be based upon the sum of the absolute or squared difference values based upon the mean value of luminance intensity of pixels of the image signal.
41 Citations
33 Claims
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1. An interframe coding system for frame-to-frame coding of an input signal, comprising:
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a subtractor having inputs to receive the input signal and a predictive signal and an output to provide a predictive error signal corresponding to a difference between the input signal and the predictive signal; an encoder having an input coupled to the output of the subtractor to receive the predictive error signal, having an output that provides a coded predictive error signal, and having a control input that receives a coding control signal for controlling a quantization step size of the encoder; decoding means for producing a decoded signal having an input coupled to the output of the encoder to receive the coded predictive error signal, having an input to receive the predictive signal, and having an output that provides the decoded signal; a frame memory having an input that receives the decoded signal and having an output that provides the predictive signal; a controller having inputs that receive the input signal and the predictive signal, that calculates a difference between the input signal and the predictive signal and generates the coding control signal based on the difference, and having an output coupled to the control input of the encoder that provides the coding control signal for controlling the encoder. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
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29. An interframe coding system for frame-to-frame coding of an input signal, comprising:
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a subtractor having inputs to receive the input signal and a predictive signal and an output to provide a predictive error signal corresponding to a difference between the input signal and the predictive signal; an encoder having an input coupled to the output of the subtractor to receive the predictive error signal, having an output that provides a coded predictive error signal, and having a control input that receives a coding control signal for controlling a quantization step size of the encoder; decoding means for producing a decoded signal having an input coupled to the output of the encoder to receive the coded predictive error signal, having an input to receive the predictive signal, and having an output that provides the decoded signal; a frame memory having an input that receives the decoded signal, and having an output that provides the predictive signal; a controller that receives the input signal and the predictive signal, that calculates an activity value from at least one of the input signal and the predictive signal and that outputs the coding control signal based on the activity value to the encoder to control the quantization step size of the encoder.
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30. An interframe coding method for frame-to-frame coding of an input signal in a coding system, wherein the coding system includes a local decoding loop including an encoder for interframe coding a predictive error signal, a subtractor that receives the input signal and a predictive signal and provides the predictive error signal corresponding to a difference between the predictive signal and the input signal, decoding means for producing a decoded signal, a frame memory for receiving the decoded signal and outputting the predictive signal, and a controller that receives the input signal and the predictive signal and provides a coding control signal to the encoder, the interframe coding method comprising the steps of:
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(a) calculating a difference, with the controller, between the input signal and the predictive signal and generating the coding control signal based on the difference; (b) selecting a step size of quantization, in the encoder, responsive to the coding control signal; and (c) coding the predictive error signal based on the selected step size of quantization.
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31. An interframe coding method for frame-to-frame coding of an input signal in a coding system, wherein the coding system includes a local decoding loop including an encoder for interframe coding a predictive error signal, a subtractor that receives the input signal and a predictive signal and provides the predictive error signal corresponding to a difference between the predictive signal and the input signal, decoding means for producing a decoded signal, a frame memory for receiving the decoded signal and outputting the predictive signal, and a controller that receives the input signal and the predictive signal and provides a control signal to the encoder, the interframe coding method comprising the steps of:
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(a) providing a characteristic signal from the controller indicating a relative characteristic of one of the input signal and the predictive signal; (b) selecting a step size of quantization, in the encoder, based on the characteristic signal; and
,(c) coding the predictive error signal based on the selected step size of quantization.
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32. An interframe coding system for frame-to-frame coding of an input signal including a local decoding loop, comprising:
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a subtractor, responsive to the input signal and a predictive signal that provides a predictive error signal corresponding to a difference between the input signal and the predictive error signal; an encoder, responsive to the predictive error signal and a coding control signal, for interframe coding of the predictive error signal and for outputting an encoded signal, the encoder selecting a step size of quantization in response to the coding control signal; a decoder, responsive to the encoded signal, that decodes the encoded signal and outputs a decoded signal; a frame memory, responsive to the decoded signal, that calculates the predictive signal, corresponding to a motion compensation prediction of the input signal based on a previous image signal, and that outputs the predictive signal; and a controller having inputs that receive the input signal and the predictive signal, that calculates a difference between the input signal and the predictive signal and that generates the coding control signal based on the difference.
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33. An interframe coding system for frame-to-frame coding of an input signal, comprising:
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a subtractor, responsive to the input signal and a predictive signal that provides a predictive error signal corresponding to a difference between the input signal and the predictive error signal; an encoder, responsive to the predictive error signal and a coding control signal, for interframe coding of the predictive error signal and for outputting an encoded signal, the encoder selecting a step size of quantization in response to the coding control signal; a decoder, responsive to the encoded signal, that decodes the encoded signal and outputs a decoded signal; a frame memory, responsive to the decoded signal, that calculates the predictive signal, corresponding to a difference between the input signal and a previous input signal, and that outputs the predictive signal; and a controller, responsive to the input signal and the predictive signal, that calculates an activity value from at least one of the input signal and the predictive signal and that outputs the coding control signal based on the activity value.
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Specification