Here are some interesting findings from some tests I have done, it appears HDCD.exe output is different then WMP decoding of HDCDs, I am still looking into this and trying other things so I may be missing something, I will post a update after trying a few more HDCDs and
chronotrom WMP wave output plugin
EDIT: My windows original direct sound capture tests shown in this post are invalid, WMP and HDCD.exe decoding of HDCD content do match when using a WMP wav out plugin, see my post below.
EDIT 2: Removed waveform as not to confuse people, see waveform in post below to see that WMP and HDCD.exe have the same output