Robin Bowes;275629 Wrote: 
> Pale Blue Ego wrote:
> > Just ran across this thread...
> > 
> > The hdcd.exe program works great!  I tried it on Emmylou's "Wrecking
> > Ball".  The resulting 24-bit FLACs sound fantastic and are only
> > slightly larger than the original 16-bit FLACs.
> 
> .... which suggests they're 16-bit 8-bits of zero padding ;)
> 
> R.
In fact, this is ALMOST true of many popular HDCDs, which is why the
decoded 24-bit file encodes to just slightly larger than the 16-bit
file.  Many of the popular music HDCDs I've processed with  hdcd.exe
only have "peak extension" mode, which only affects the waveform peaks.
So for most of the disc, the 16-bit samples are just shifted down one
bit (to make room for the peaks to be extended) by placing a 0 bit at
the top and more 0s at the bottom.

One side effect of passing audio through hdcd.exe, whether it is HDCD
encoded or not is that it reduces the level by 6 dB (one bit).  The
design intent was that the HDCD decoder would be in the DAC, so it
could also reduce everything by 6 dB.  Of course the listener would
simply compensate by turning up theor volume control a bit.

The problem comes when you have a file that has been passed through
hdcd.exe and one which has not.  Presumably one would only be passing
HDCD encoded discs through hdcd.exe and not processing regular CDs
through hdcd.exe.  This was NOT the intent of the implementors of HDCD;
they intended for everything, HDCD or not, to be reduced by 6 dB by the
HDCD DAC.

One solution to this is ReplayGain, which will recognize that hdcd.exe
has reduced the level by 6 dB and make a corresponding adjustment to
the ReplayGain value.


-- 
Timothy Stockman
------------------------------------------------------------------------
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View this thread: http://forums.slimdevices.com/showthread.php?t=32967

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