Encoding apparatus, decoding apparatus, encoding method and decoding method

An encoding apparatus, comprising:

• a picture element memory for receiving and storing a picture element having a value within a predetermined range as an encoding picture element, and for outputting a value of an encoded picture element adjacent to the encoding picture element as the value of a reference picture element;
• a mode determinator for selecting one of a specific encoding mode and an encoding mode other than the specific encoding mode from a plurality of predefined encoding modes for the encoding picture element based on the value of the reference picture element;
• a first encoding section for predicting the value of the encoding picture element, determining whether the prediction is correct, encoding the value of the encoding picture element based on a result of the determination, and for outputting a codeword for the encoding picture element;
• a second encoding section for predicting the value of the encoding picture element, encoding the value of the encoding picture element, and for outputting a codeword for the encoding picture element;
• and
• an encoding controller for selectively operating said first encoding section and said second encoding section based on a selected result of said mode determinator, and
• wherein said first encoding section comprises:
• a first predictor for calculating a prediction value of the encoding picture element based on the value of the reference picture element;
• a first prediction error calculator for calculating an error between the value of the encoding picture element and the prediction value calculated by said first predictor as a prediction error;
• a determinator for determining whether the prediction error calculated by said first prediction error calculator is a specific value, and for outputting a result of the determination;
• a first encoder for receiving and encoding the result of the determination output from said determinator, and for outputting the codeword for the encoding picture element to be encoded in the selected specific encoding mode;
• and
• a second encoder for encoding the prediction error calculated by said first prediction error calculator when the prediction error is other than the specific value for the encoding picture element to be encoded in the selected specific encoding mode, and for outputting the codeword for the encoding picture element to be encoded in the selected specific encoding mode,
• wherein based on information as to which one of the binary symbols is a more probable symbol and an estimated occurrence probability of the more probable symbol, at least one of the first encoder and the second encoder implements encoding for an extended information source of the binary symbols effected by selecting a code most suited to a state of the extended information source of the binary symbols assumed from the estimated occurrence probability of the more probable symbol from a set of Huffman codes prepared systematically for the extended information source of the binary symbols.

A decoding apparatus, comprising:

• a picture element memory for storing decoded picture elements having values within a predetermined range, and outputting the value of one of the decoded picture elements adjacent to a decoding picture element as a value of a reference picture element;
• a mode determinator for selecting one of a specific decoding mode and a decoding mode other than the specific decoding mode from a plurality of predefined decoding modes for the decoding picture element based on the value of the reference picture element;
• a first decoding section for receiving a codeword, predicting a value of the decoding picture element, determining whether the prediction is correct, and for decoding the codeword into the value of the decoding picture element based on a result of the determination;
• a second decoding section for receiving a codeword for the decoding picture element, predicting the value of the decoding picture element, decoding the codeword;
• and
• a decoding controller for selectively operating said first decoding section and said second decoding section based on a selected result of said mode determinator;
• wherein said first decoding section comprises:
• a first predictor for calculating a prediction value of the decoding picture element based on the value of the reference picture element;
• a first decoder for decoding the codeword for the decoding picture element to be decoded in the selected specific decoding mode into a result of determination indicating whether a prediction error is a predetermined value;
• a second decoder for decoding the codeword for the decoding picture element to be decoded in the selected specific decoding mode and having the prediction error other than the predetermined value into the prediction error other than the predetermined value;
• and
• a first decoding picture element calculator for calculating the value of the decoding picture element based on the prediction value of the decoding picture element calculated by said first predictor, the result of the determination, and the prediction error obtained by said second decoder;
• wherein the mode determinator receives the value of the reference picture element output from said picture element memory and the result of the determination output from said first decoder, and selects the decoding mode based on the value of the reference picture element and the result of the determination.

A decoding apparatus, comprising:

• a picture element memory for storing decoded picture elements having values within a predetermined range, and outputting the value of one of the decoded picture elements adjacent to a decoding picture element as a value of a reference picture element;
• a mode determinator for selecting one of a specific decoding mode and a decoding mode other than the specific decoding mode from a plurality of predefined decoding modes for the decoding picture element based on the value of the reference picture element;
• a first decoding section for receiving a codeword, predicting a value of the decoding picture element, determining whether the prediction is correct, and for decoding the codeword into the value of the decoding picture element based on a result of the determination;
• a second decoding section for receiving a codeword for the decoding picture element, predicting the value of the decoding picture element, and decoding the codeword;
• and
• a decoding controller for selectively operating said first decoding section and said second decoding section based on a selected result of said mode determinator, and
• wherein said first decoding section comprises:
• a first predictor for calculating a prediction value of the decoding picture element based on the value of the reference picture element;
• a first decoder for decoding the codeword for the decoding picture element to be decoded in the selected specific decoding mode into a result of determination indicating whether a prediction error is predetermined value;
• a second decoder for decoding the codeword for the decoding picture element to be decoded in the selected specific decoding mode and having the prediction error other than the predetermined value into the prediction error other than the predetermined value;
• and
• a first decoding picture element calculator for calculating the value of the decoding picture element based on the prediction value of the decoding picture element calculated by said first predictor, the result of the determination, and the prediction error obtained by said second decoder,
• wherein based on information as to which one of the binary symbols is a more probable symbol and an estimated occurrence probability of the more probable symbol, at least one of the first decoder and the second decoder implements decoding for an extended information source of binary symbols effected by selecting a code most suited to a state of the extended information source of binary symbols assumed from the estimated occurrence probability of the more probable symbol from a set of Huffman codes prepared systematically for the extended information source of binary symbols.

An encoding method comprising:

• an outputting step of receiving and storing a picture element having a value within a predetermined range as an encoding picture element, and outputting a value of an encoded picture element adjacent to the encoding picture element as the value of a reference picture element;
• a mode deciding step of selecting one of a specific encoding mode and an encoding mode other than the specific encoding mode from a plurality of predefined encoding modes for the encoding picture element based on the value of the reference picture element;
• a first main encoding step of predicting the value of the encoding picture element, determining whether the prediction is correct, encoding the value of the encoding picture element based on a result of determination, and outputting a codeword for the encoding picture element;
• a second main encoding step of predicting the value of the encoding picture element, encoding the value of the encoding picture element, and outputting a codeword for the encoding picture element;
• and
• an encoding controlling step of selectively operating said first main encoding step and said second main encoding step based on a selected result of said mode deciding step;
• wherein said first main encoding step comprises:
• a first predicting step of calculating a prediction value of the encoding picture element based on the value of the reference picture element;
• a first prediction error calculating step of calculating an error between the value of the encoding picture element and the prediction value calculated by said first predicting step as a prediction error;
• a determination step of determinating whether the prediction error calculated by said first prediction error calculating step is a predetermined value, and outputting a result of the determination;
• a first encoding step of receiving and encoding the result of the determination output by said determination step and outputting the codeword for the encoding picture element to be encoded in the selected specific encoding mode;
• and
• a second encoding step of encoding the prediction error calculated by said first prediction error calculating step when the prediction error is other than the predetermined value for the encoding picture element to be encoded in the selected specific encoding mode, and outputting the codeword for the encoding picture element to be encoded in the selected specific encoding mode;
• wherein the mode deciding step receives the value of the reference picture element output from said outputting step and the result of the determination output from said determination step, and selects the encoding mode based on the value of the reference picture element and the result of the determination.

An encoding method, comprising:

• an outputting step of receiving and storing a picture element having a value within a predetermined range as an encoding picture element, and outputting a value of an encoded picture element adjacent to the encoding picture element as the value of a reference picture element;
• a mode deciding step of selecting one of a specific encoding mode and an encoding mode other than the specific encoding mode from a plurality of predefined encoding modes for the encoding picture element based on the value of the reference picture element;
• a first main encoding step of predicting the value of the encoding picture element, determining whether the prediction is correct, encoding the value of the encoding picture element based on a result of determination, and outputting a codeword for the encoding picture element;
• a second main encoding step of predicting the value of the encoding picture element, encoding the value of the encoding picture element, and outputting a codeword for the encoding picture element;
• and
• an encoding controlling step of selectively operating said first main encoding step and said second main encoding step based on a selected result of said mode deciding step, and
• wherein said first main encoding step comprises:
• a first predicting step of calculating a prediction value of the encoding picture element based on the value of the reference picture element;
• a first prediction error calculating step of calculating an error between the value of the encoding picture element and the prediction value calculated by said first predicting step as a prediction error;
• a determination step of determining whether the prediction error calculated by said first prediction error calculating step is a predetermined value, and outputting a result of the determination;
• a first encoding step of receiving and encoding the result of the determination output by said determination step and outputting the codeword for the encoding picture element to be encoded in the selected specific encoding mode;
• and
• a second encoding step of encoding the prediction error calculated by said first prediction error calculating step when the prediction error is other than the predetermined value for the encoding picture element to be encoded in the selected specific encoding mode, and outputting the codeword for the encoding picture element to be encoded in the selected specific encoding mode;
• wherein based on information as to which one of the binary symbols is a more probable symbol and an estimated occurrence probability of the more probable symbol, at least one of the first encoding step and the second encoding step implements encoding for an extended information source of the binary symbols effected by selecting a code most suited to a state of the extended information source of the binary symbols assumed from the estimated occurrence probability of the more probable symbol from a set of Huffman codes prepared systematically for the extended information source of the binary symbols.

A decoding method, comprising:

• an outputting step of storing decoded picture elements having values within a predetermined range, and outputting the value of one of the decoded picture elements adjacent to a decoding picture element as the value of a reference picture element;
• a mode deciding step of selecting one of a specific decoding mode and a decoding mode other than the specific decoding mode from a plurality of predefined decoding modes for the decoding picture element based on the value of the reference picture element;
• a first main decoding step of receiving a codeword, predicting a value of the decoding picture element, determining whether the prediction is correct, and decoding the codeword into the value of the decoding picture element based on a result of the determination;
• a second main decoding step of receiving a codeword, predicting the value of the decoding picture element, and decoding the codeword into the value of the decoding picture element;
• and
• a decoding controlling step of selectively operating said first main decoding step and said second main decoding step based on a selected result of said mode deciding step;
• wherein said first main decoding step comprises:
• a first predicting step of calculating a prediction value of the decoding picture element based on the value of the reference picture element;
• a first decoding step of decoding the codeword for the decoding picture element to be decoded in the selected specific decoding mode into a result of determination indicating whether a prediction error is a predetermined value;
• a second decoding step of decoding the codeword for the decoding picture element to be decoded in the selected specific decoding mode and having the prediction error other than the predetermined value into the prediction error other than the predetermined value;
• and
• a first decoding picture element calculating step of calculating the value of the decoding picture element based on the prediction value for the decoding picture element calculated by said first predicting step, the result of the determination, and the prediction error other than the predetermined value obtained by said second decoding step;
• wherein the mode deciding step receives the value of the reference picture element output from said outputting step and the result of the determination output from said first decoding step, and selects the decoding mode based on the value of the reference picture element and the result of the determination.

A decoding method, comprising:

• an outputting step of storing decoded picture elements having values within a predetermined range, and outputting the value of one of the decoded picture elements adjacent to a decoding picture element as the value of a reference picture element;
• a mode deciding step of selecting one of a specific decoding mode and a decoding mode other than the specific decoding mode from a plurality of predefined decoding modes for the decoding picture element based on the value of the reference picture element;
• a first main decoding step of receiving a codeword, predicting a value of the decoding picture element, determining whether the prediction is correct, and decoding the codeword into the value of the decoding picture element based on a result of the determination;
• a second main decoding step of receiving a codeword, predicting the value of the decoding picture element, and decoding the codeword into the value of the decoding picture element;
• and
• a decoding controlling step of selectively operating said first main decoding step and said second main decoding step based on a selected result of said mode deciding step, and
• wherein said first main decoding step comprises:
• a first predicting step of calculating a prediction value of the decoding picture element based on the value of the reference picture element;
• a first decoding step of decoding the codeword for the decoding picture element to be decoded in the selected specific decoding mode into a result of determination indicating whether a prediction error is a predetermined value;
• a second decoding step of decoding the codeword for the decoding picture element to be decoded in the selected specific decoding mode and having the prediction error other than the predetermined value into the prediction error other than the predetermined value;
• and
• a first decoding picture element calculating step of calculating the value of the decoding picture element based on the prediction value for the decoding picture element calculated by said first predicting step, the result of the determination, and the prediction error other than the predetermined value obtained by said second decoding step, and
• wherein said second main decoding step comprises:
• a second predicting step of calculating a prediction value of the decoding picture element based on the value of the reference picture element;
• a third decoding step of decoding the codeword for the decoding picture element to be decoded in the selected decoding mode other than the specific decoding mode into a prediction error regardless of whether the prediction error is the predetermined value;
• and
• a second decoding picture element calculating step of calculating the value of the decoding picture element to be decoded in the selected decoding mode other than the specific decoding mode based on the prediction value calculated by said second predicting step and the prediction error calculated by said third decoding step,
• wherein said first decoding step comprises a first symbol restoring step for receiving the codeword and decoding the codeword into a sequence of binary symbols and a first probability estimating step of estimating an occurrence probability of one of the binary symbols, and a step of outputting one of the binary symbols as a result of the determination,
• wherein said second decoding step comprises a second symbol restoring step of receiving the codeword and decoding the codeword into a sequence of binary symbols, a second probability estimating step of estimating an occurrence probability of one of the binary symbols, and a first symbol-to-error converting step of receiving the sequence of binary symbols and converting the sequence of binary symbols into the prediction error,
• wherein said third decoding step comprises a third symbol restoring step of receiving the codeword and decoding the codeword into a sequence of binary symbols, a third probability estimating step of receiving the binary symbols and estimating an occurrence probability of one of the binary symbols, and a second symbol-to-error converting step of receiving the sequence of binary symbols and converting the sequence of binary symbols into the prediction error, and
• wherein at least one of said first symbol restoring step, said second symbol restoring step, and said third symbol restoring step includes a step of changing interpretation as to which one of the binary symbols is a more probable symbol based on a change in probability estimation for the binary symbols respectively implemented by said first probability estimating step for said first symbol restoring step, said second probability estimating step for said second symbol restoring step, and said third probability estimating step for said third symbol restoring step;
• wherein based on information as to which one of the binary symbols is a more probable symbol and
• an estimated occurrence probability of the more probable symbol, at least one of the first symbol restoring step, the second symbol restoring step, and the third symbol restoring step implements decoding for an extended information source of binary symbols effected by selecting a code most suited to a state of the extended information source of binary symbols assumed from the estimated occurrence probability of the more probable symbol from a set of Huffman codes prepared systematically for the extended information source of binary symbols.

A picture processing apparatus for receiving picture signals representing picture elements, encoding the picture elements represented by the picture signals into codes by using an encoding apparatus therein, and for outputting the codes to a subsequent processing apparatus, the encoding apparatus comprising:

• a picture element memory for receiving and storing a picture element having a value within a predetermined range as an encoding picture element, and for outputting a value of an encoded picture element adjacent to the encoding picture element as the value of a reference picture element;
• a mode determinator for selecting one of a specific encoding mode and an encoding mode other than the specific encoding mode from a plurality of predefined encoding modes for the encoding picture element based on the value of the reference picture element;
• a first encoding section for predicting the value of the encoding picture element, determining whether the prediction is correct, encoding the value of the encoding picture element based on a result of the determination, and for outputting a codeword for the encoding picture element;
• a second encoding section for predicting the value of the encoding picture element, encoding the value of the encoding picture element, and for outputting a codeword for the encoding picture element;
• and
• an encoding controller for selectively operating said first encoding section and said second encoding section based on a selected result of said mode determinator;
• wherein the first encoding section comprises:
• a first predictor for calculating a prediction value of the encoding picture element based on the value of the reference picture element;
• a first prediction error calculator for calculating an error between the value of the encoding picture element and the prediction value calculated by the first predictor as a prediction error;
• a determinator for determinating whether the prediction error calculated by the first prediction error calculator is a specific value, and for outputting a result of the determination;
• a first encoder for receiving and encoding the result of the determination output from the determinator, and for outputting the code word for the encoding picture element to be encoded in the selected specific encoding mode;
• and
• a second encoder for encoding the prediction error calculated by the first prediction error calculator when the prediction error is other than the specific value for the encoding picture element to be encoded in the selected specific encoding mode, and for outputting the codeword for the encoding picture element to be encoded in the selected specific encoding mode, wherein the mode determinator receives the value of the reference picture element output from said picture element memory and the result of the determination output from said determinator, and selects the encoding mode based on the value of the reference picture element and the results of the determination.

A picture processing apparatus comprising:

• a picture pick-up device for picking up a picture composed of a plurality of picture elements;
• a picture compression circuit for compressing the picked-up picture;
• and
• a memory for storing the compressed picture,
• wherein said picture compression circuit includes an encoding apparatus comprising:
• a picture element memory for receiving and storing a picture element having a value within a predetermined range as an encoding picture element, and for outputting a value of an encoded picture element adjacent to the encoding picture element as the value of a reference picture element;
• an encoding section for predicting the value of the encoding picture element, determining whether the prediction is correct, encoding the value of the encoding picture element based on a result of the determination, and for outputting a codeword for the encoding picture element;
• and
• an encoding controller for controlling an operation of the encoding section based on the result of the prediction made by the encoding section, wherein the encoding section comprises:
• a predictor for calculating a prediction value of the encoding picture element based on the value of the reference picture element;
• a prediction error calculator for calculating an error between the value of the encoding picture element and the prediction value calculated by the predictor as a prediction error;
• a determinator for determining whether the prediction error calculated by the prediction error calculator is a predetermined value and for outputting a result of determination;
• a first encoder for receiving the result of determination output from the determinator, encoding the result of determination, and for outputting the codeword;
• and
• a second encoder for encoding the prediction error calculated by the prediction error calculator when the prediction error is other than the predetermined value for the encoding picture element to be encoded and for outputting the codeword for the encoding picture element to be encoded, wherein based on information as to which one of the binary symbols is a more probable symbol and an estimated occurrence probability of the more probable symbol, at least one of the first codeword allotter and the second codeword allotter implements encoding for an extended information source of the binary symbols effected by selecting a code most suited to a state of the extended information source of the binary symbols assumed from the estimated occurrence probability of the more probable symbol from a set of Huffman codes prepared systematically for the extended information source of the binary symbols.

A picture processing apparatus for receiving a picture signal representing a code for a picture element, decoding the code into the value of the picture element by a decoding apparatus therein, and for outputting the picture element to a subsequent processing apparatus, the decoding apparatus comprising:

• a picture element memory for storing decoded picture elements having values within a predetermined range and outputting the value of one of the decoded picture elements adjacent to a decoding picture element as the value of a reference picture element;
• a mode determinator for selecting one of a specific decoding mode and a decoding mode other than the specific decoding mode from a plurality of predefined decoding modes for the decoding picture element based on the value of the reference picture element;
• a first decoding section for receiving a codeword, predicting a value of the decoding picture element, determining whether the prediction is correct, and for decoding the codeword into the value of the decoding picture element based on a result of the determination;
• a second decoding section for receiving a codeword the decoding picture element, predicting the value of the decoding picture element, and for decoding the codeword into the value of the decoding picture element;
• and
• a decoding controller for selectively operating the first decoding section and the second decoding section based on a selected result of said mode determinator;
• wherein said first decoding section comprises:
• a first predictor for calculating a prediction value of the decoding picture element based on the value of the reference picture element;
• a first decoder for decoding the codeword for the decoding picture element to be decoded in the selected specific decoding mode into a result of determination indicating whether a prediction error is a predetermined value;
• a second decoder for decoding the codeword for the decoding picture element to be decoded in the selected specific decoding mode and having the prediction error other than the predetermined value into the prediction error other than the predetermined value;
• and
• a first decoding picture element calculator for calculating the value of the decoding picture element based on the prediction value of the decoding picture element calculated by said first predictor, the result of the determination, and the prediction error obtained by said second decoder;
• wherein the mode determinator receives the value of the reference picture element output from said picture element memory and the result of the determination output from said first decoder, and selects the decoding mode based on the value of the reference picture element and the result of the determination.

An encoding method comprising:

• an outputting step of receiving and storing a picture element having a value within a predetermined range as an encoding picture element, and outputting a value of an encoded picture element adjacent to the encoding picture element as the value of a reference picture element;
• a mode deciding step of selecting one of a specific encoding mode and an encoding mode other than the specific encoding mode from a plurality of predefined encoding modes for the encoding picture element based on the value of the reference picture element;
• a first main encoding step of predicting the value of the encoding picture element, determining whether the prediction is correct, encoding the value of the encoding picture element based on a result of determination, and outputting a codeword for the encoding picture element;
• a second main encoding step of predicting the value of the encoding picture element, encoding the value of the encoding picture element, and
• outputting a codeword for the encoding picture element;
• and
• an encoding controlling step of selectively operating the first main encoding step and the second main encoding step based on a selected result of the mode deciding step, and
• wherein the first main encoding step comprises:
• a first predicting step of calculating a prediction value of the encoding picture element based on the value of the reference picture element;
• a first prediction error calculating step of calculating an error between the value of the encoding picture element and the prediction value calculated by the first predicting step as a prediction error a determination step of determinating whether the prediction error calculated by the first prediction error calculating step, is a predetermined value, and outputting a result, of the determination;
• a first encoding step of receiving and encoding the result of the determination output by the determination step and outputting the codeword for the encoding picture element to be encoded in the selected specific encoding mode;
• and a second encoding step of encoding the prediction error calculated by the first prediction error calculating step when the prediction error is other than the predetermined value for the encoding picture element to be encoded in the selected specific encoding mode, and outputting the codeword for the encoding picture element to be encoded in the selected specific encoding mode, and
• wherein the second main encoding step comprises:
• a second predicting step of calculating a prediction value of the encoding picture element based on the value of the reference picture element;
• a second prediction error calculating step of calculating an error between the value of the encoding picture element and the prediction value calculated by the second predicting step as a prediction error;
• and
• a third encoding step of encoding the prediction error calculated by the second prediction error calculating step for the encoding picture element to be encoded in the selected encoding mode other than the specific encoding mode, regardless of whether the prediction error is the predetermined value, and outputting the codeword for the encoding picture element to be encoded in the selected encoding mode other than the specific encoding mode,
• wherein the first encoding step comprises a first probability estimating step of receiving the result of the determination output by the determination step as a sequence of binary symbols and estimating an occurrence probability of one of the binary symbols and a first codeword allotting step of encoding the sequence of binary symbols,
• wherein the second encoding step comprises a first error-to-symbol converting step of receiving the prediction error and converting the prediction error into a sequence of binary symbols,
• a second probability estimating step of receiving the sequence of binary symbols and estimating an occurrence probability of one of the binary symbols, and a second codeword allotting step of encoding the sequence of binary symbols, and
• wherein the third encoding step comprises a sec and error-to-symbol converting step of receiving the prediction error and converting the prediction error into a sequence of binary symbols, a third probability estimating step of receiving the sequence of binary symbols and estimating an occurrence probability of one of the binary symbols, and a third codeword allotting step of encoding the sequence of binary symbols, and
• wherein based on information as to which one of the binary symbols is a more probable symbol and
• an estimated occurrence probability of the more probable symbol, at least one of the first codeword allotting step, the second codeword allotting step, and the third codeword allotting step implements encoding for an extended information source of the binary symbols effected by selecting a code most suited to a state of the extended information source of the binary symbols assumed from the estimated occurrence probability of the more probable symbol from a set of Huffman codes prepared systematically for the extended information source of the binary symbols.

A decoding method, comprising:

• an outputting step of storing decoded picture elements having values within a predetermined range, and outputting the value of one of the decoded picture elements adjacent to a decoding picture element as the value of a reference picture element:
• a mode deciding step of selecting one of a specific decoding mode and a decoding mode other than the specific decoding mode from a plurality of predefined decoding modes for the decoding picture element based on the value of the reference picture element;
• a first main decoding step of receiving a code word, predicting a value of the decoding picture element, determining whether the prediction is correct, and decoding the codeword into the value of the decoding picture element based on a result of the determination;
• a second main decoding step of receiving a codeword, predicting the value of the decoding picture element, and decoding the codeword into the value of the decoding picture element;
• and
• a decoding controlling step of selectively operating the first main decoding step and the second main decoding step based on a selected result of the mode deciding step,
• wherein the first main decoding step comprises:
• a first predicting step of calculating a prediction value of the decoding picture element based on the value of the reference picture element a first decoding step of decoding the codeword for the decoding picture element to be decoded in the selected specific decoding mode into a result of determination indicating whether a prediction error is a predetermined value;
• a second decoding step of decoding the codeword for the decoding picture element to be decoded in the selected specific decoding mode and having the prediction error other than the predetermined value into the prediction error other than the predetermined value;
• and
• a first decoding picture element calculating step of calculating the value of the decoding picture element based on the prediction value for the decoding picture element calculated by the first predicting step, the result of the determination, and the prediction error other than the predetermined value obtained by the second decoding step,
• wherein based on information as to which one of the binary symbols is a more probable symbol and an estimated occurrence probability of the more probable symbol, at least one of the first decoding step and the second decoding step implements decoding for an extended information source of binary symbols effected by selecting a code most suited to a state of the extended information source of binary symbols assumed from the estimated occurrence probability of the more probable symbol from a set of Huffman codes prepared systematically for the extended information source of-binary symbols.

An encoding apparatus, comprising:

• a picture element memory for receiving and storing a picture element having a value within a predetermined range as an encoding picture element, and for outputting a value of an encoded picture element adjacent to the encoding picture element as the value of a reference picture element;
• an encoding section for predicting the value of the encoding picture element, determining whether the prediction is correct, encoding the value of the encoding picture element based on a result of the determination, and for outputting a codeword for the encoding picture element;
• and
• an encoding controller for controlling an operation of the encoding section based on the result of the prediction made by the encoding section, wherein the encoding section comprises:
• a predictor for calculating a prediction value of the encoding picture element based on the value of the reference picture element;
• a prediction error calculator for calculating an error between the value of the encoding picture element and the prediction value calculated by the predictor as a prediction error;
• a determinator for determining whether the prediction error calculated by the prediction error calculator is a predetermined value and for outputting a result of determination;
• a first encoder for receiving the result of determination output from the determinator, encoding the result of determination, and for outputting the codeword;
• and
• a second encoder for encoding the prediction error calculated by the prediction error calculator when the prediction error is other than the predetermined value for the encoding picture element to be encoded and for outputting the codeword for the encoding picture element to be encoded,
• wherein based on information as to which one of the binary symbols is a more probable symbol and an estimated occurrence probability of the more probable symbol, at least one of the first codeword allotter and the second codeword allotter implements encoding for an extended information source of the binary symbols effected by selecting a code most suited to a state of the extended information source of the binary symbols assumed from the estimated occurrence probability of the more probable symbol from a set of Huffman codes prepared systematically for the extended information source of the binary symbols.

A decoding apparatus comprising:

• a picture element memory for storing decoded picture elements having values within a predetermined range and for outputting the value of one of the decoded picture elements adjacent to a decoding picture element as the value of a reference picture element a decoding section for receiving a codeword, predicting a value of the decoding picture element, determining whether the prediction is correct, and for decoding the codeword into the value of the decoding picture element based on a result of the determination;
• and
• a decoding controller for controlling an operation of the decoding section based on the result of the determination made by the decoding section,
• wherein the decoding section comprises:
• a predictor for calculating a prediction value for the decoding picture element based on the value of the reference picture element;
• a first decoder for decoding a result of determination showing whether a prediction error is a predetermined value;
• a second decoder for decoding the codeword for the decoding picture element whose prediction error is not the predetermined value into the prediction error;
• a decoding picture element calculator for calculating the value of the decoding picture element based on the prediction value calculated by the predictor, the result of the determination, and the prediction error obtained by the second decoder,
• wherein based on information as to which one of the binary symbols is a more probable symbol and an estimated occurrence probability of the more probable symbol, at least one of the first symbol restoring device and the second symbol restoring-device implements decoding for an extended information source of binary symbols effected by selecting a code most suited to a state of the extended information source of binary symbols assumed from the estimated occurrence probability of the more probable symbol from a set of Huffman codes prepared systematically for the extended information source of binary symbols.

An encoding method, comprising:

• an outputting step of receiving and storing a picture element having a value within a predetermined range as an encoding picture element, and for outputting a value of an encoded picture element adjacent to the encoding picture element as the value of a reference picture element;
• an encoding step of predicting the value of the encoding picture element, determining whether the prediction is correct, encoding the value of the encoding picture element based on a result of the determination, and for outputting a codeword for the encoding picture element;
• and
• an encoding controlling step of controlling an operation of the encoding step based on the result of the prediction made by the encoding step wherein the encoding step comprises:
• a predicting step of calculating a prediction value of the encoding picture element based on the value of the reference picture element;
• a prediction error calculating step of calculating an error between the value of the encoding picture element and the prediction value calculated by the predicting step as a prediction error;
• a determinating step of determining whether the prediction error calculated by the prediction error calculating step is a predetermined value and for outputting a result of determination;
• a first encoding step of receiving the result of determination output from the determinating step, encoding the result of determination, and of outputting the codeword;
• and
• a second encoding step of encoding the prediction error calculated by the prediction error calculating step when the prediction error is other than the predetermined value for the encoding picture element to be encoded and of outputting the codeword for the encoding picture element to be encoded,
• wherein based on information as to which one of the binary symbols is a more probable symbol and an estimated occurrence probability of the more probable symbol, at least one of the first codeword allotting step and the second codeword allotting step implements encoding for an extended information source of the binary symbols effected by selecting a code most suited to a state of the extended information source of the binary symbols assumed from the estimated occurrence probability of the more probable symbol from a set of Huffman codes prepared systematically for the extended information source of the binary symbols.

A decoding method, comprising:

• an outputting step of storing decoded picture elements having values within a predetermined range and of outputting the value of one of the decoded picture elements adjacent to a decoding picture element as the value of a reference picture element;
• a decoding step of receiving a-codeword, predicting a value of the decoding picture element, determining whether the prediction is correct, and of decoding the codeword into the value of the decoding picture element based on a result of the determination;
• and
• a decoding controlling step of controlling an operation of the decoding step based on the result of the determination made by the decoding step,
• wherein the decoding step comprises:
• a predicting step of calculating a prediction value for the decoding picture element based on the value of the reference picture element;
• a first decoding step of decoding a result of determination showing whether a prediction error is a predetermined value;
• a second decoding step of decoding the codeword for the decoding picture element whose prediction error is not the predetermined value into the prediction error;
• a decoding picture element calculating step of calculating the value of the decoding picture element based on the prediction value calculated by the predicting step, the result of the determination, and the prediction error obtained by the second decoding step,
• wherein based on information as to which one of the binary symbols is a more probable symbol and
• an estimated occurrence probability of the more probable symbol, at least one of the first symbol restoring step and the second symbol restoring step implements decoding for an extended in formation source of binary symbols effected by selecting a code most suited to a state of the extended information source of binary symbols assumed from the estimated occurrence probability of the more probable symbol from a set of Huffman codes prepared systematically for the extended information source of binary symbols.