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What is HDCD? - Page 2

post #16 of 19

HDCD makes (dollars and sense) = bang for buck!

Microsoft bought the parent/licensing company for HDCD last year. So we have Mr. Softie in the format fray with Sony/Philips and the DVD-A folks. Remember how Microsoft sometimes likes to resolve things?

My inexpensive Denon DCM-370 was a major sound improvement over the 1-bit eight-year-old Yamaha it replaced last year, both on Redbook and HDCD discs. This year, I've redone my analog front end, and am enjoying my old vinyl like never before. I am not buying any more vinyl, but vinyl is in my cultural history for at least half of my listening life. And the new analog equipment makes the old LPs sound MUCH better than old or cheap digital. (That's some crow I've had to eat . . . )

HDCD seems to license a lot of material for a couple of extra bucks per CD, or about half of SACD/DVD-A prices. HDCD represents a quantum step up from redbook, but the artists who license under it are already more concerned than most about the sound quality of their recordings. I think I will go to a better Denon with 24 bit decoding, as I have already scored a bunch of good CDs at good discounts which would benefit from this. On the cheap, the Denon DVM-3700 offers HDCD and 24 bit and is discounted to around $550 as it is being superceded by the DVM-4800.
post #17 of 19
Originally posted by neil
I have a CD that seems to pop in and out of HDCD mode on a per-track basis. And in fact, one of the tracks, on the last 10 seconds (fade-out) the HDCD light on the CDP turns off. Weird, eh?
Actually, I don't think it is weird, as I have noticed the same thing on a few compilation discs. My thinking is that individual songs can be recorded in the HDCD format and still decoded, even on a disc that is not wholly HDCD. That's my best guess, anyway.
post #18 of 19
About false triggering:
For material not recorded using the encoder, a small probability for a false trigger does
exist. Given a moderate length for the scrambling shift register so that its mapping behaves
in a noise-like fashion and a choice of synchronizing pattern which avoids patterns likely to
appear in audio data with a higher than average probability, susceptibility to false triggers
can be made arbitrarily small by increasing the length of the part of the packet requiring a
match. In the case of the current system, the combination of the synchronizing pattern with
the bit equivalence for all valid commands plus check sum results in a required match
equivalent to 39 sequential bits. For a stereo signal, in which a match must occur in both
channels within a one second interval and the commands in both channels must specify the
same gains, this amounts to an expectation of one event in approximately 150 million years
of audio.
That quote is from the HDCD Technical Paper, found here

I'd say that a pretty good guess to what's happening when HDCD decoding turns off during fades and so on is that either the manufacturer of the CD, or a second mastering engineer (such as a compilation mastering engineer), is doing things with the audio signal that effectivly ruins the HDCD code. Doing a fade or a gain change (such as normalizing when ripping - beware! ) will do this.


post #19 of 19



HDCD actually uses 1 bit of a 16 bit audio word to manipulate a HDCD decoding chip (digital filter) so that you obtain 20 bit resolution on a 16 bit format.

This means you get 20 bit singal to noise ratio and 20 bit dynamic range and so on.

Sony / Phillips redbook audio defined a standard compact audio disc to have 16 bits resolution , 2 or 4 channels and a sample rate of 44100 hz.

If the disc is 4 channel it is played at 2 X (twice as fast as an stereo audio CD).

HDCD also is brave enough to say that the 1 bit that is now used to manipulate the digital filter (HDCD capable) can not be heard.

i.e the one bit that would normally be used for audio is now used for control information and yours ears will not hear a difference.

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