Ignore the other channel on bottom, simply compare the top (played on Denon DVD-9000, (attenuated by Emotiva XSP-1, recorded by Tascam DA-3000) with the bottom (original AIF file copied from CD by iTunes).
Here is visual comparison of a transient with HDCD decoding, and the raw "no-effect HDCD" digital data (having no other feathers than Transient Flag enabled). The decoding is done to 24/96 from the one player which I thought there was still hope might implement the Transient Flag, the rare and expensive Denon DVD-9000 (which claimed next generation HDCD decoding, one of the first not to use PMD100). To see the effect of the transient flag, one would have to use a higher sampling rate (I used 24/96 in recording the transient on top...that should be sufficient to show a variable playback filter if it existed).
Nevertheless, they look identical. Comparing the two graphs I sometimes see a new detail on one, but then when I go and check the other, it has that same identical detail too, as often happens in subjective audio comparisons. (To "hear differences" may mean not bothering to go back and check when something allegedly "new" is hear.)
Now actually, I don't know that Transient flag is operative on this stretch of audio, it was just the most visibly clear transient in the first track of Fresh Aire III "on HDCD" which has Transient Flags enabled but uses no other HDCD features (peak extension or gain adjustment).
I always thought this Fresh Aire box set sounded especially magical on HDCD players. However the best evidence now is that in every case it was just lighting the HDCD light, and doing nothing more (on the user side...it did indicate you had an authentically unaltered HDCD recording made with Pacific Microsonics Analog to Digital Converters (either the One or Two).
And those converters were said to be among the best sounding ever... Many used them because of that AND because of the convenient Peak and Gain Adjustment features, which meant setting setting the exact levels was less important and you didn't have to worry as much about clipping since far out peaks were automatically compressed (and then re-expanded by an HDCD decoder).
When the HDCD Peak and Gain features ARE used, as much as 1 bit or 6dB of effective dynamic range is added (about 4.5dB on the album Mephisto & Co. according to my measurements). This is not always insignificant. Inexpensive audio equipment including preamps and amplifiers can have 10-20dB more dynamic range than conventional CD's...120dB. We can experience at least 130dB (but I recommend not going above 110dB for sake of your hearing).
The argument that the Objectophiles make is that acoustic noise makes this irrelevant. I don't accept that...acoustic noise is something fundamentally different.
It makes sense to use 24/96 (or 24/88) and nothing higher, as those are essentially beyond the capabilities of even the best audio electronics anyway and can't in any way be felt to be inadequate.
And most of the benefit comes from the first extra bit and bump in sampling rate.
In theory, HDCD did both, with the second coming from a variable playback filter that could be bumped up and down to make transients more transient. It also made it possible to distribute "media" and "audiophile" versions of recordings at the same time, with audiophiles (who aren't seeking maximum loudness) getting the benefit of the wider (closer to the limits of perception) dynamic range.
The standard story is the variable playback filter was never implemented because the patent for such variable filters was owned by Ed Meitner of Museatex. HDCD still uses a variable filter prior to digitization, where it's most important anyway, and that's what triggers the flag. Many experts say that even if implemented the effects of the variable playback filter would be very marginal.
That appears to be the case, and my doubts are mostly evaporated by this test.
But HDCD still delivers nice sounding encoder/decoders with almost 1 bit of dynamic range added. It's only irrelevant now because true high definition like 24/96 is so easily accessed (if it's even made available).
HDCD files should be expanded if they can't easily be played on HDCD dacs (which are becoming harder to find). Expanders include HDCD.exe, Foobar2000, and ffmpeg. I use ffmpeg, which is said to use good code from Foobar2000 if you see the HDCD statistics being reported.
Since these decoders were based on reverse engineering, it's possible that licensed decoders in players are slightly more accurate. But it hardly matters for the peaks we are talking about. And it's likely the software decoders are in fact quite accurate as many Objectophiles poured considerable effort into getting them correct.
There is no need to do anything when only the Transient Flag is enabled.
AFAIK and according to these data, anyway.
No comments:
Post a Comment