Subband image coding and decoding

Abstract

In encoding an input picture signal, the input signal is split by subband splitting into plural frequency bands for generating signals of plural frequency bands, and the signals of the respective frequency bands are quantized for generating quantized signals of the respective frequency bands. From these quantized signals of the respective frequency band, the coefficients existing at the same spatial positions of the respective layers resulting from spectrum splitting are extracted for generating a coefficient tree. This coefficient tree is S-scanned in a direction proceeding from the low frequency band towards the high frequency band for generating a scan sequence which is run-length encoded for generating encoded data. In decoding the encoded data, obtained as described above, is decoded by run-length decoding for generating a scan sequence from which a coefficient tree is re-constructed. The coefficients of the re-constructed coefficient tree located at the same spatial positions in the respective layers and the coefficients located at the same spatial positions are dequantized for generating signals of the plural frequency bands. These signals are decoded by subband decoding for reproducing the original input picture signal.