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In Reply to: By the way, here are some stats on the non decoded vs decoded outputs posted by Christine Tham on December 24, 2005 at 00:28:38:
So let's review what we've learned here:1) Microsoft's implementation of HDCD decoding is different in WMP than it is for stand-alone CD players. I had no idea that this was the case, and I have no idea why they would do this.
2) By comparing the non-decoded output of an HDCD disc versus the decoded output, you can tell if "peak extend" was used in the recording. I hadn't thought of this method before, and this is a useful tool. (This method cannot be used with stand-alone CD players.)
On these points, the facts are self-evident and there is no room for disagreement.
Next you claim that by comparing the non-decoded output of an HDCD disc versus the decoded output, you can *probably* tell if "low level extension" was used in the recording. In this case the evidence is not quite as clear as with "peak extend", so I will reserve judgement on this. The statistical analysis you posted clearly shows a 6 dB shift in levels (as noted in point #1 above). Once this is compensated for, the biggest difference between the files is less than 0.5 dB (for "minimum RMS power"). Without further information, I don't think we can say one way or the other. In theory this method should work, but it is likely to be tedious, and I'm not clear that you've correctly identified a disc employing "low level extension".
And finally we return to the reading comprehension issue. You claim to "destroy [my] theory", but the problem is that you are setting up a straw man. I never said what you claim.
The HDCD encoder has two compansion schemes that are optionally engaged by the mastering engineer -- "peak extend" and "low level extension". (Furthermore, there are two varieties of "low level extension".) However if BOTH of these are *not* engaged, then there is no need for HDCD decoding.
I will recap one more time, in hopes that this will sink in:
1) When HDCD was introduced, it represented a true sonic breakthrough for the CD format. This was because the HDCD encoder was head and shoulders superior to the only other widely available choice at that time -- the horrible sounding Sony 1630. However, most of the gains found with HDCD were due to the encoder's features that DO NOT require decoding:
a) Dithering.
b) Switchable on-the-fly anti-alias filters.
c) Keith Johnson's discrete analog circuitry, excellent power supplies, and low-jitter clocks.
Nowadays there are many great sounding A/D converters available (none of them with HDCD encoding), but 10 years ago it was a completely different story. And while there are still many HDCD encoders in use, there are none available for sale today.
2) Unless an HDCD disc was recorded with "peak extend" and/or "low level extension", there is nothing for an HDCD playback machine to decode. Hence there is no advantage to using an HDCD-capable player with these discs.
You and I have both described methods to distinguish HDCD discs using "peak extend" from HDCD discs that do not use "peak extend". It may be possible that your method is also able to distinguish discs that use "low level extension". What is yet to be determined is what percentage of HDCD discs use "peak extend" and/or "low level extension" and would therefore benefit from HDCD decoding.
Please note that I never said that these type of discs *wouldn't* benefit from HDCD decoding. Instead, what I said was that HDCD decoding didn't provide the full benefits commonly ascribed to it for two reasons:
a) Much of the sonic benefit from HDCD discs does not derive from the HDCD process per se.
b) Many (we don't know how many) HDCD discs are not encoded in such a way as to require decoding.
Follow Ups:
*** On these points, the facts are self-evident and there is no room for disagreement. ***I think you will now agree that previously when you were asserting that I was not able to distinguish between discs that have peak extend or not, you were wrong. Also, when you persisted in calling me wrong in my description of what WMP does, you were also wrong.
Again, perhaps an apology would be in order?
*** Once this is compensated for, the biggest difference between the files is less than 0.5 dB (for "minimum RMS power"). Without further information, I don't think we can say one way or the other. ***
I've already said: further information is there, by inspecting and comparing the actual shape of the waveforms. You are more than welcome to repeat what I've done, and evaluate the differences yourself. What you will find is that these differences are on every HDCD disc (or at least in my case every single HDCD I own).
*** The HDCD encoder has two compansion schemes that are optionally engaged by the mastering engineer -- "peak extend" and "low level extension". (Furthermore, there are two varieties of "low level extension".) However if BOTH of these are *not* engaged, then there is no need for HDCD decoding. ***
No, you are still wrong. Unlike Peak Extend, the low level manipulations are NOT optional. Again, read the patent.
*** I will recap one more time, in hopes that this will sink in ***
Your recap is still wrong, and is not consistent with what the patent says.
*** Much of the sonic benefit from HDCD discs does not derive from the HDCD process per se. ***
This is debatable, since it is merely your opinion, and you have not provided any substantiation for this statement. Any it is clearly wrong for discs with Peak Extend, but we can argue about whether the benefits of dynamic filter switching and low level gain manipulation is "substantial."
*** Many (we don't know how many) HDCD discs are not encoded in such a way as to require decoding. ***
You are wrong, because the low level gain manipulation is NOT optional. It's related to the way HDCD does dithering.
You are amazing in your persistence in being wrong. You must love to be wrong. Repeat after me:THE PATENT IS NOT THE PRODUCT.
THE PATENT IS NOT THE PRODUCT.
THE PATENT IS NOT THE PRODUCT.
Please refer to the operating manual for the Pacific Microsonics Model Two HDCD encoder:
==========
Low Level Extension is an average signal level based low level compression / expansion
system used on HDCD 16-bit amplitude encoded recordings which very gradually raises
gain a preset amount when the average signal level drops below a preset threshold. During
HDCD 16-bit decoded playback the compression curve is expanded back to linear gain by
the HDCD decoder using a precisely mapped inverse of the compression curve controlled by
a hidden code, producing a dynamic range and resolution floor beyond 16-bit. During
undecoded playback low level information normally lost by standard 16-bit players is preserved,
providing more accurate timbral and spatial reproduction.
There are two modes of Low Level Extension, “Normal” and “Special”. Normal mode begins
to affect the input signal 45 dB below peak level, gradually raising the gain 4 dB as the
level drops over an 18 dB range. Special mode begins to affect the input signal 39 dB
below peak level, and gradually raises the gain 7.5 dB over a 26 dB range.Use of Low Level Extension is optional in the HDCD 16-bit encoding process.
==========Since you apparently have a problem with reading compehension, I will repeat this last point:
USE OF LOW LEVEL EXTENSION IS OPTIONAL IN THE HDCD 16-BIT ENCODING PROCESS.
You seem to have a real aversion to reading the patent, but prefer to quote from a specific implementation.If you did read the patent, you may realise what the patent refers to as "low level gain manipulation" refers a broad number of things, including low level extension. It is not a synonym for low level extension.
Anyway, the proof is in the empirical results, which you have ignored. Again, based on my experience, the WMP HDCD decoder seems to manipulate all HDCD content, regardless of whether specific features are engaged or disengaged.
If you can find a specific HDCD disc that passes through the WMP HDCD decoder unscathed, then perhaps you may have a point. But I'm willing to bet you can't.
Christine wrote, "HDCD is defined by the patent, not the implementation."Yep, I'm pretty sure that's the way it works in real life.
There they are in the mastering studio, getting ready to create the master for their new album. The band is there, the producer is there, and the mastering engineer there, all working hard to make the best product they can. The studio is equipped with a Pacific Microsonics Model Two A/D converter (which along with the Model One is the only way there is to make an HDCD disc).
They are debating which settings to use, and then someone shouts, "STOP! We have to check with the patent!"
So they go on-line and download the patent. They discuss it for a while and then agree, that even though there are menu options for turning "low level extension" on and off, and even though these options are explained in the manual, that they MUST NOT turn off "low level extension". After all, that's what it says in the patent.
Tell me something, Charles, have you ever been in a recording studio? Have you been involved in mastering any recordings? Do you actually have any idea at all what constitutes "real life" in a studio?
One of my best friends (whom I have known for over 30 years) is a well-established recording engineer. His credits include Alanis Morissette, Ringo Starr, and Dada. I have sat in on several recording sessions with him.I have also sat in on mastering sessions with George Marino (Sterling Sound), David Glasser (Airshow Mastering), and Gus Skinas (Super Audio Center). If you haven't heard of these guys, do a Google search and see what you find out.
So yes, I do have an idea of what constitutes "real life" in a studio. And I must say that not once in all my times in a studio has someone been concerned about looking up a patent, even though in some cases these people were actually using an HDCD encoder. Funny, that.
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