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US 6,212,495 B1Granted
Coding method, coder, and decoder processing sample values repeatedly with different predicted values
AssigneeOki Electric Industry Co., Ltd.
InventorKeiichi Chihara
Life of this patent
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Abstract
A differential pulse-code modulation coder obtains an improved signal-to-noise ratio, with only a small increase in bit rate, by repetitive coding. In one aspect, the coder divides the input signal into frames, codes each frame repeatedly using different prediction coefficients or different quantizing step functions, and selects the coefficient or step function that produces the least quantization error. In another aspect, the coder repeats the coding of individual samples located in the outermost steps of the quantizing step function.
Claims33
A coding method comprising the steps of:
- (a) receiving successive sample values of an audio signal;
- (b) calculating a predicted value of a current sample value among the successive sample values in said audio signal;
- (c) calculating a difference between said current sample value and said predicted value;
- (d) quantizing said difference, obtaining a quantized value;
- (e) coding said quantized value, obtaining coded data;
- (f) calculating a predicted value of a next sample value among the successive sample values in said audio signal from the predicted value and the quantized value of said current sample value;
- and
- (g) repeating said steps (b) to (f) for said current sample value, using at least one different predicted value in said step (b).
5 more elements
A coder, comprising:
- an input terminal receiving an audio signal having sample values grouped into frames;
- a subtractor coupled to said input terminal, said subtractor taking a difference between a current sample value in said audio signal and a predicted value of said current sample value, thereby obtaining a difference value;
- a quantizing and coding unit coupled to said subtractor, quantizing and coding said difference value, thereby obtaining a quantized value and coded data representing said quantized value;
- an error calculator coupled to said quantizing and coding unit, calculating a quantization error for each frame of said sample values;
- a predictor coupled to said quantizing and coding unit, using said quantized value, the predicted value of said current sample value, and a coefficient to calculate a predicted value of a next sample value in said audio signal;
- and
- a coefficient selector coupled to said predictor, providing said coefficient to said predictor, causing said predictor and said quantizing and coding unit to code each said frame repeatedly using different values of said coefficient, selecting a value of said coefficient that produces a least quantization error for said frame, causing said quantizing and coding unit to output the coded data produced using the selected value of said coefficient, and appending information identifying said selected value to the coded data output for said frame.
4 more elements
A coder, comprising:
- an input terminal receiving an audio signal having sample values grouped into frames;
- a subtractor coupled to said input terminal, said subtractor taking a difference between a current sample value in said audio signal and a corresponding predicted value, thereby obtaining a difference value;
- a quantizing and coding unit coupled to said subtractor, using a step function to quantize and code said difference value, thereby obtaining a quantized value and coded data representing said quantized value;
- an error calculator coupled to said quantizing and coding unit, calculating a quantization error for each frame of said sample values;
- a predictor coupled to said quantizing and coding unit, calculating a predicted value of a next sample value in said audio signal from the quantized value and the predicted value of said current sample value;
- and
- a step-function selector coupled to said quantizing and coding unit, providing said step function to said quantizing and coding unit, causing said predictor and said quantizing and coding unit to code each said frame repeatedly using different step functions, selecting a step function that produces a least quantization error for said frame, causing said quantizing and coding unit to output the coded data produced using the selected step function, and appending information identifying said selected step function to the coded data output for said frame.
4 more elements
A coder, comprising:
- an input terminal receiving an audio signal having sample values grouped into frames;
- a predictor calculating a predicted value of a current sample value in said audio signal;
- a subtractor coupled to said input terminal and said predictor, taking a difference between aid current sample value and said predicted value, thereby obtaining a difference value;
- a quantizing and coding unit coupled to said subtractor, quantizing and coding said difference value, thereby obtaining a quantized value and coded data representing said quantized value;
- and
- a repetition controller coupled to said quantizing and coding unit, causing said predictor, said subtractor, and said quantizing and coding unit to process said current sample value again, using a different predicted value of said current sample value, when said coded data represent a maximum absolute quantized value.
3 more elements
A coding method, comprising the steps of:
- (a) providing a sequence of sample values derived from an analog information signal that carries information about a stimulus perceptible to a human sense organ;
- (b) calculating a predicted value of a current sample value among the successive sample values in said information signal;
- (c) calculating a difference between said current sample value and said predicted value;
- (d) quantizing said difference, obtaining a quantized value;
- (e) coding said quantized value, obtaining coded data;
- (f) calculating a predicted value of a next sample value among the successive sample values in said information signal from the predicted value and the quantized value of said current sample value;
- and
- (g) repeating said steps (b) to (f) for said current sample value, using at least one different predicted value in said step (b).
5 more elements
Dependencies are inferred from the claim text.