Bit rate reduction of enhancement layer in bit-depth scalable coding

In this report, we propose a bit-depth scalable coding system based on the integer wavelet transform. Encoder of the system outputs two layered bit-streams. Decoding the base layer, upper part of the bit planes of each pixel values of an input image signal are displayed. Adding the enhancement layer, all the bit planes are reconstructed without any loss. Since quantization errors in the transformed domain are amplified by the backward transform in the local decoding, we move the quantization to the spatial domain. As a result, the errors are not amplified and the bit rate of the enhancement layer is reduced by 8.4 [%] on average over some image signals.