ITU-T Recommendations

ITU-T T.801 | ISO/IEC 15444-2 specifies the enhancement of the selective arithmetic coding bypass (lazy mode) defined in ITU-T T.800 | ISO/IEC 15444-1.
The selective arithmetic coding bypass is the coding style which allows bypassing the arithmetic coder for the significance propagation (SP) pass and magnitude refinement (MR) passes starting in the 5th significant bit-plane of the code-block. The coding style default marker (COD), or the coding style component marker (COC), signals where or not this coding style is used. The first clean-up (CP) pass, which is the first bit-plane of a code-block with a non-zero element, and the next three sets of SP, MR, and CP coding passes, are decoded with the arithmetic coder. The fourth CP pass shall include an arithmetic coder termination.
Starting with the fourth SP and MR coding passes, the bits that would have been returned from the arithmetic coder are instead returned directly from the bit stream. After each MR pass, the bit stream has been "terminated" by padding to the byte boundary.
In this Amendment 4 to ITU-T T.801 | ISO/IEC 15444-2, the enhancement of the lazy mode (fast mode) is presented. The fast mode allows the flexible selection of the number of bit planes to be coded by normal coding passes. The fast mode takes advantage of the following points to speed up the coding time and maintain the compression efficiency.
The reduction of the number of bit planes to be coded by the SP pass and the MR pass with an arithmetic coder will contribute to the reduction of coding time.
The compression ratio of JPEG 2000 lossless is roughly 2 to 3, according to many experimental results. The compression possibility of the 2nd or 3rd bit plane, and after looking from the most significant bit (MSB), is very low in many cases because of its statistic feature of 50-50 distribution of binary data.