ENCODING APPARATUS FOR HIERARCHICALLY ENCODING IMAGE SIGNAL AND DECODING APPARATUS FOR DECODING THE IMAGE SIGNAL HIERARCHICALLY ENCODED BY THE ENCODING APPARATUS

摘要

Important quantized coefficients of which absolute values are higher than a threshold-value are extracted from each of quantized coefficient streams into which a digital image signal is transformed, and an important quantized coefficient stream composed of the important quantized coefficients and zero-valued quantized coefficients is produced on condition that the number of important quantized coefficients and zerovalued quantized coefficients is equal to that of quantized coefficients in each quantized coefficient stream and positions of the important quantized coefficients in the important quantized coefficient stream are the same as those in a corresponding quantized coefficient stream. Also, a lesser-important quantized coefficient stream is produced by subtracting the important quantized coefficient stream from the corresponding quantized coefficient stream. High precision type error correction codes are added to each important quantized coefficient stream and are transmitted to a decoding apparatus, and low precision type error correction codes are added to each lesser-important quantized coefficient stream and are transmitted to the decoding apparatus. Therefore, an image having a superior quality can be reproduced with a high code efficiency.