The above link probably explains it better than I can, but it's Sony's patented dithering process to go from 24 or 20 bits down to the 16/44.1 redbook CD standard. Their goal is to capture more than 16 bits of sound in the 16-bit format. They claim that it makes a 16 bit CD sound more like 20 bits of information. Many of the Columbia/Legacy reissues use the SBM process and I think most sound quite good.
What is Super Bit Mapping
I just bought a cd on Sony, Tchaikovsky and Sibelius Violin concertos, Isaac Stern and the Philadelphia Orchestra under Eugene Ormandy. The playing is superb and the sound quality very high, at least on first hearing. A sticker was added on the front of the jewel case proclaiming SBM. What is it? What are the advantages or disadvantages of this process.