INVERSE DISCRETE COSINE TRANSFORM METHOD, INVERSE DISCRETE TRANSFORM APPARATUS, CODING APPARATUS FOR MOVING PICTURE, INFORMATION RECORDING MEDIUM, AND TRANSMITTING APPARATUS

摘要

A PICTURE SIGNAL IS SUBJECTED TO MOTION COMPENSATING PREDICTIVE-CODING BY USING A REFERENCE PICTURE ALREADY REPRODUCED BY A SUBTRACTER 8, AND THE SIGNAL THUS CODED IS CAUSED TO UNDERGO DCT TRANSFORM,QUANTIZATION AND VARIABLE LENGTH CODING BY A DIFFERENCE SIGNAL ENCODER 9 AND A VLC ELEMENT 17. THE VARIABLE LENGTH CODE THUS OBTAINED IS TRANSMITTED AS A BIT STREAM TO A DECODING APPARATUS FOR A MOVING PICTURE OR AN INFORMATION RECORDING MEDIUM. FURTHER, AN OUTPUT OF THE DIFFERENCE SIGNAL ENCODER 9 IS CAUSED TO UNDERGO INVERSE-QUANTIZATION AND IDCT PROCESSING BY A DIFFERENCE SIGNAL DECODER 10. THEREAFTER, A PICTURE SIGNAL OF A REFERENCE PICTURE IS ADDED THERETO BY AN ADDER 16 TO REPRODUCE A PICTURE SIGNAL. IN ALLOWING THE PRODUCED PICTURE TO BE A NEXT REFERENCE PICTURE, AN ODDIFICATION OPERATION ELEMENT 14 OF THE DIFFERENCE SIGNAL DECODER 10 IMPLEMENTS AN OPERATION TO AT LEAST ONE DCT COEFFICIENT SO THAT SUM OF DCT COEFFICIENTS FROM AN INVERSE QUANTIZER 13 IS ODD NUMBER TO DELIVER, TO AN IDCT CIRCUIT 15, DCT COEFFICIENTS OF WHICH SUM IS ODDIFIED, THEREBY MAKING IT POSSIBLE TO EFFECTIVELY PREVENT OCCURENCE OF DISCRETE COSINE TRANSFORM MISS-MATCH ERROR. THUS DETERIORATION OF PICTURE QUALITY CAN BE PREVENTED.(FIG. 6)