A data communication method for a data communication system including a data transmission apparatus and a data receiving apparatus, the method comprising the steps of:
- applying scalable-encoding processing by using wavelet transform to an image signal;
- generating a packet which stores scalable-encoded data generated in the encoding step and specifying priority-level information corresponding to a layer of the scalable-encoded data of the image signal, stored in the generated packet, as additional information of the generated packet, both steps being executed in the data transmission apparatus;
- and
- decoding data stored in a packet to which the information of a level of priority equal to or larger than a value specified according to a processing performance of the data receiving apparatus is assigned, the decoding step being executed in the data receiving apparatus.