A low memory QCB-based DWT for JPEG2000 coprocessor supporting large tile size

JPEG2000, which provides a higher compression ratio than the traditional JPEG, is an upcoming compression standard for still images. The experimental results imply that the larger tile size used for JPEG2000 results in better image quality. However, processing the large tile image requires more memory in the hardware implementation. To reduce the hardware resources, a QCB (quad codeblock) based DWT method is proposed to support the processing of large tile images with low memory. Based on the QCB-based DWT engine, three code-blocks belonging to LH₀, HL₀ and HH₀ bands can be generated recursively after each fixed time slice, and the EBC (embedded block coding) processors can directly process the three code-blocks. It can save the size of tile memory by up to 75%. Moreover, the remaining 1/4 size of tile memory can be decreased through the zero holding extension for unavailable data. That is, it only requires 24 Kbytes memory to support the processing of a 512×512 tile image, with slight image degradation, especially at low bit rates. The low memory requirement makes the hardware implementation practicable.