Method and apparatus for discrete cosine transform/inverse discrete cosine transform

A discrete cosine transform (DCT)/inverse discrete cosine transform (IDCT) method causing an operation device to perform one or more of a DCT operation and an IDCT operation, the DCT/IDCT method comprising:

• recognizing the number of input values other than 0 (zero) out of input values of coordinates in an input block and comparing the recognized number of input values with a predetermined reference value;
• and
• performing a table-based transform method out of a row-column decomposition-based method and the table-based transform method only when the number of input values other than 0 is equal to or less than the reference value, wherein the table-based transform method includes:
• generating a table index for only an input value other than 0 out of the input values of the coordinates in the input block;
• reading one or more partial values corresponding to the table index out of a plurality of table information pieces which are generated and stored in advance so as to include partial values corresponding to a multiplication of a weight value and an index;
• and
• adding the read partial values and calculating a resultant value of each coordinate in an output block, and
• wherein the number of input values other than 0 is recognized with reference to the number of level values in the course of entropy coding.

A discrete cosine transform (DCT)/inverse discrete cosine transform (IDCT) device performing one or more of a DCT operation and an IDCT operation, the DCT/IDCT device comprising:

• a row-column decomposition-based operation unit that performs a DCT/IDCT operation based on row-column decomposition;
• a table-based operation unit that performs a table-based DCT/IDCT operation;
• and
• a method selecting unit that recognizes the number of input values other than 0 (zero) out of the input values of coordinates in an input block, compares the recognized number of input values with a predetermined reference value, and instructs the row-column decomposition-based operation unit or the table-based operation unit to perform an operation,
• wherein the table-based operation unit includes:
• a table information storage unit that stores a plurality of table information pieces including partial values corresponding to a multiplication of a weight value and an index;
• an index calculating unit that generates a table index of only an input value other than 0 out of the input values of the coordinates in the input block;
• and
• an adder unit that adds one or more partial values included in the plurality of table information pieces and corresponding to the table index and calculates resultant values of coordinates in an output block, and
• wherein the method selecting unit for an MPEG-4 part10 AVC/H.264 codec recognizes the number of input values other than 0 using information on the number of input values other than 0 which is calculated and stored as a parameter in advance.

A discrete cosine transform (DCT)/inverse discrete cosine transform (IDCT) method causing an operation device to perform one or more of a DCT operation and an IDCT operation, the DCT/IDCT method comprising:

• recognizing the number of input values other than 0 (zero) out of input values of coordinates in an input block and comparing the recognized number of input values with a predetermined reference value;
• and
• performing a table-based transform method out of a row-column decomposition-based method and the table-based transform method only when the number of input values other than 0 is equal to or less than the reference value,
• wherein the table-based transform method includes:
• generating a table index for only an input value other than 0 out of the input values of the coordinates in the input block;
• reading one or more partial values corresponding to the table index out of a plurality of table information pieces which are generated and stored in advance so as to include partial values corresponding to a multiplication of a weight value and an index;
• and
• adding the read partial value values and calculating a resultant value of each coordinate in an output block, and
• wherein the number of input values other than 0 for an MPEG-4 part10 AVC/H. 264 codec is recognized using information on the number of input values other than 0 which is calculated and stored as a parameter in advance.