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RE: THE TRUTH ABOUT HDCD (For the 39th time)

>> From my limited experience with HDCDs, peak extension is used quite extensively. One way to identify PE is that at moderate sound levels an HDCD sounds 6dbs louder undecoded than decoded. <<

That is a good low-tech way to check for PE. Probably not 100% accurate, but pretty close.

It's funny that you mentioned Foobar. It turns out that as of this summer they have a plug-in HDCD decoder that will report if a track is "HDCD" and also look at the state of the three playback bits in the hidden code:

- HDCD ("yes" or "no")

- Peak Extend ("yes" or "no")

- Low-Level Extension (expressed as a gain level added to the signal, ranging from 0.0 dB, which is no LLE applied to -7.5 dB, which is the maximum amount of LLE gain)

- Transient Filter ("yes" or "no")

PLEASE NOTE -- ANY disc made with the PM A/D converter will light up the "HDCD" light (a metaphorical one in the case of Foobar). The PM inserts the hidden code whether or not it needs to.

PLEASE NOTE -- While there are two anti-aliasing filters used during the A/D conversion while making a disc, THERE IS ONLY ONE PLAYBACK FILTER. I have no idea why the information regarding which filter was used during recording was included in the hidden code. I have guesses, but they are unimportant.

~~~~~~~~~~

Therefore, the only features which can be decoded are PE and LLE.

More importantly, we have a way to *know* if any decoding is required. I searched my music library for an "HDCD" disc and the first one I found was a retrospective triple disc set by David Crosby entitled "Voyage".

Here is the screen shot from Foobar:



If you look at the bottom of the screen you will see that it is an "HDCD" disc. However, neither PE nor LLE are engaged and therefore no decoding is required. (The Transient Filter occasionally jumps to yes. It is so quick that you don't even have time to read it, only to see that something changed briefly. Again, this doesn't matter as it doesn't require decoding.)

So there you have it -- a great example of a FAKE "HDCD" disc. It was made with the PM A/D converter, but the mastering engineer didn't engage any of its features and there is NO decoding required. This box set is from 2006. I am sure that the vast majority of HDCD discs made in the last five years will not require any decoding.

If you have a Windows machine, it may be worth installing Foobar just to "look" at your HDCD discs. You don't even have to rip them as Foobar will play them straight from your drive.

I'll keep looking and see if I can find more examples. I know that I have Joni's "Hits" and "Misses" albums around here somewhere. I would bet that they require decoding as they are much older and a big deal was made about the use of HDCD when they came out. But we shall see...

EDIT: This disc is actually NOT a "FAKE" HDCD disc. It turns out that LLE was engaged for this disc. I missed it because during virtually all of the songs, the LLE level remained pegged at +0.0 dB. However, in between tracks, the level would drop low enough that the LLE would apply a -4.0 dB dynamic range expansion. Fairly useless, because, the silence between tracks doesn't really need much help in that department.

The only place I have seen any LLE applied during the music was at the beginning of "Wooden Ships". The song starts with the muffled strumming of guitar strings, and for the first few seconds of the song the LLE varied between 0.0 and -2.5 dB.

But even a very quiet and mellow song like "Guinnevere" had no LLE during the entire song. And that is just two acoustic guitars, joined by two vocal parts. This confirms what I have heard from people who have reverse-engineered the code -- the LLE is almost never used in actual practice.


Edits: 12/31/10
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