It is currently implemented in libopenraw in ljpegdecompressor.cpp
- ljpeg seems to be the only C reference implementation, and, according to the JPEG-FAQ, has bugs with 16-bits. This is the code that was used as a based for libopenraw implementation.
- Adobe DNG SDK seems to use an adaptation of the former, in C++. Too bad the license isn’t GPL compatible.
- jrawio in Java has an implementation that seems to work.
- dcraw, RawSpeed and libraw also implements it.