Coding method

A method for decoding an image block by block from an encoded bit stream, said method comprising analyzing the encoded bit stream to obtain difference information indicating that a difference between a quantization parameter for a current block and a parameter of quantization for a previous block located immediately before the current block in the processing order, wherein a value of zero is assigned to said difference information when the current block is an intracoded pulse modulation (IPCM) block; determining a quantization parameter for the current block, using the quantization parameter for the previous block and the difference information, regardless of whether the current block is an IPCM block or a different intracoded pulse modulation block, other than IPCM; determining a filtering intensity of the deblocking filtering using an average value of the quantization parameter for the current block and the quantization parameter for the previous block, the filtering intensity being determined so that it increases with increasing average value of the quantization parameter for absorb a quantization error; and performing unblocking filtering on a boundary between the previous block and the current block using the determined filtering intensity of unblocking filtering, wherein performing unblocking filtering comprises determining whether at least any one of the previous block and the current block is an IPCM block and apply unblocking filtering only to pixels in the non-IPCM blocks.