HDCD CDs and transcoding

[Soli]

Its probably patented etc.
At least according to Wikipedia: In 2007, a member of the Doom9 forum authored a Windows CLI utility, hdcd.exe, to extract and decode the HDCD data in 16-bit WAV files ripped from HDCD discs. This utility writes 24-bit WAV output files with four bits of padding per sample. The author of the utility decided not to make the source code publicly available as the HDCD technology is patented.[10]

HDCD are 2 things: a good ADC with dither/noiseshaping, and the specific HDCD features, where Peak Extend is more or less the only one that matters.
In isolation HDCD is a quite simple "DBX" type process that use the signals coded/buried within LSB to tell the HDCD decoder how much the signal should be expanded. HDCD with peak extension have the possibility to sound better than normal CDs, it can sound close to a real 19-20bit properly mastered file. Not because HDCD has any real 20 bit resolution, the max resolution is still 16bit, but using peak extend and dither/noiseshaping you can have 16it sound down to approx -20-24db (the number MAY be inaccurate but the point would be the same). And the dynamic range can almost be the same as 20bit, but with 16bit resolution. These features, along with the Pacific Microsonic ADC which is among the worlds best ADCs, along with proper mastering (since HDCD is actually an ADC process, you are mostly spared the ultra evil digital loudness war mastering), will result in a really good sounding music But the good sounding music is not the result of HDCD itself, if you turn off peak extend, it will still sound good, and it will sound better on DAC that don't support HDCD.

Heres a picture that illustrates the waveform when peak extend is properly decoded:
http://i60.photobucket.com/albums/h39/mo.../gdwav.jpg

Since peak extend makes the recording sounding worse, most studios that use the HDCD processors for their sound quality , actually turn peak extend off.