HDCD augments CD quality in just the required ways to make it slightly better. It might not be as good as true high resolution PCM at 88/24, but close (I guess HDCD gets about 50% of the audible benefit of 88/24). Most people think about the dynamic range expanding. That's part of it, but another part is the variable digital filter*, which optimizes either low distortion (mostly) or transients (when they are important).
One way or another, CD's using HDCD encoding should best be decoded with HDCD. This, from the beginning, was the biggest complaint. It's not "truly" compatible. But the same limitation may apply to nearly everything "compatible," and then there are lots of things like DVD-Audio which are not compatible.
Nowadays I play back HDCD's on my Denon DVD-9000, which is one of the best HDCD players ever. It has the second generation HDCD decoder...but it's not an actual HDCD chip. It's embedded in the firmware, which also includes AL24, Denon's upconverting oversampling system. Along with that, the DVD-9000 has dual differential Burr Brown 1704 Dacs, the best true PCM DAC chip ever made. After the 1704, everyone went to the cheaper Sigma Delta approach. 1704's continued to be used in Levinson and other high end DACs for awhile. The power supplies and build quality of the 40 pound DVD-9000 are beyond reproach, however the analog IC's could be better, though they are a notch above the preceding DVD-5000.
But, to make this work with digital crossovers and DSP, I must convert the analog output of the DVD-9000 to digital (using my Lavry AD10) in order to get the decoding. I convert the output to 24/96 high resolution digital so the HDCD decoding is fully captured.
Starting last year, I added a new way of "streaming" HDCD's from my library or music services. I put a dedicated Sonos Zoneplayer (a ZP80) sending PCM (with the HDCD bits if they happen to be there) to the digital input of my DVD-9000.
But sometime last year I borrowed that Sonos unit to serve as a second Sonos analog input in the kitchen. That never really worked for various reasons. The main reason for doing it was so that I could have a Sonos input dedicated to my Kenwood L-1000T tuner. But about the same time, I decided to switch to the slightly quieter and always pleasant sounding Sansui TU-D99X, the last TOTL tuner from Sansui featuring their custom made Walsh MPX decoder. It only has one output.
In over a year of "borrowing" the second ZP80 for the kitchen, I don't recall ever actually using it beyond the first test. Now I also have a 3-way switch feeding the main ZP80 in the kitchen, so I could send audio from the Mac, the Pioneer DVD recorder, or the tuner. It should not be necessary to send audio from the Oppo BDP-95 because it rides with the HDMI signal, which is sent to other rooms through a 4x4 matrix switch. I capture the audio from HDMI in the living room (as of last month) with a de-embedder, and I capture the audio from HDMI in the bedroom by digital optical from the TV to a DAC. The digital optical means that TV (and all it connects to) are electrically isolated from the stereo to prevent hum.
Re-installing the living room de-embedder enabled me to remove the second ZP80 from the kitchen and put it back into HDCD-streaming service in the Living Room, which I was happy to finally be able to do last night.
But one curious thing is that when using the DVD-9000 as an HDCD decoder and DAC, it does not necessarily display the HDCD logo when a digital signal with HDCD is being decoded. In fact the last time around I never saw the HDCD logo light up, but I did tests to be sure (by testing dynamic range) that the HDCD decoding was actually being done. This is a quirk of the player that other people have commented about online. When playing HDCD discs, the light always comes on.
This time, I noticed something different. I noticed that while playing some titles, the HDCD light DOES come on. It comes on particularly for the Mannheim Steamroller Fresh Aire II HDCD. But on several HDCD's from Reference Recordings, which you'd think would be the most HDCD of all, it does not come on.
When using the player as a DAC, it seems the light is triggered only by the presence of certain HDCD features in the digital signal. It may indeed require the "dynamic range upward expansion" feature, in order for the light to come on. If the digital signal has only the variable digital filter feature, it's possible it does not come one.
And that may be why Reference Recordings tend not to make the light turn on. They might not use the upward expansion feature as much--precisely in order to be "more compatible."
For titles in which the HDCD light comes on, it comes on identically for using both the Sonos controlling software, and Roon. Both Sonos and Roon are leaving the bits alone.
I believe I've seen as much as 3dB dynamic range expansion with HDCD's. Last night I measured 2dB expansion from Fresh Aire II. Unlike some later players, the Denon DVD-9000 actually puts out more signal voltage when the dynamic range expansion is occurring, up to 3.5V RMS or so. A friend of mine complained about this in 1990, and panned HDCD players as a result. Later players simply play HDCD's at a softer level to allow the peak expansion to occur. You can imagine that helped "kill" the format as discs seemed to play softer on average, and louder always sells better.
Hydrogen Audio has a good, though slanted, overview of the HDCD format. Their view is mostly derogatory, but their technical information is mostly excellent and otherwise hard to get. It's hard to read this without seeing how they're trying to get in a dig whenever they can, such as by first mentioning Microsoft as the Owner instead of the original inventor and owner, and then, when they finally get around to mentioning the famous inventor, they misname them "Pacific Microsonic" (PM) instead of "Pacific Microsonics Inc. (PMI). If someone doesn't even bother to pronounce or spell your name correctly, it's pretty much a giveaway that they are disparaging you. And then, what exactly does it mean to call a format "dead." A factual but non-derogatory description would simply be that new titles and hardware are not beling released. (For the folks at Hydrogen Audio, even claiming that anything is audibly better than CD format is basically forbidden.)
The HDCD wikipage at Hydrogen Audio alleges to echo the late Charlie Hanson (a competitor having his own slow and leaky "linear phase filter") in claiming that HDCD could not use variable playback filters because of a Meitner patent. I'm not sure if this story is 100% true. If you take the time to read Hanson's original comments at Hydrogen Audio, he nevertheless recommends using a hardware decoder (as I am doing) as "the gold standard" because of the fully correct implementation of dynamic range expansion. I spoke to Reference Recording people around 2010, and that is exactly what they recommended, and they also agreed with my approach of analog sampling the output of an HDCD decoder in high resolution digital for downstream DSP processing. Using Foobar or HDCD.exe to do the dynamic range decoding is known not to be as accurate (or at least claimed, by Charlie Hanson, others dispute this).
I have not seen a fully convincing debunking of the claimed transient filter selection anywhere. Along with Hanson, there are small number of audio objectivist cranks (who don't believe high resolution is needed either) say it was never used because of the Meitner patent. But they don't actually show any proof that HDCD players don't use the transient filter selection feature or link to verifiable information.* Meanwhile, there are numerous text and graphs show the effects of the dynamic range expansion, which is relatively easy to implement in conversion software (but apparently not always perfectly).
In this long thread about HDCD at Steve Hoffman's site, there is only one commenter, Jedi Joker, denying the utility of the transient filter function.
HDCD might have been very very useful...if it had been used like this: a single CD has two versions, the undecoded version with little dynamic range (like all standard CD's these days) and the HDCD decoded version with much more dynamic range, for those who demand it. That kind of feature is offered nowhere other than HDCD as far as I know.
The transient filter sounds like a very good idea also. That might capture 50% of the benefit of 88.2kHz sampling rate above 44.1, if in fact it were implemented. That Meitner--an early supporter of Sony's SACD project--would block full implementation of HDCD is dastardly. My only experience with a Meitner product was at a hifi society store demo where the Meitner amplifer society members wanted to hear burned out driving Apogee speakers.
And there are some very good sounding HDCD's. That's why it's worth having some kind of HDCD decoding. One of these is the Reference Recordings Mephisto and Company. Without decoding, it sounds very good. With decoding, it's a one of a kind sonic knockout. Most other HDCD's show similar differences with and without decoding. So for me it's worth having HDCD decode capability, even if it was somewhat of a scam in the beginning. (And strangely, Mephisto and Company does NOT light the HDCD light on my Denon while streaming. And yet it appears to have the maximum amount of HDCD expansion, approaching 6dB peak expansion, while the Mannheim Steamroller discs do light the light, with only about 3dB expansion. I suppose I should get one of the HDCD exploration tools mentioned in the threads above to see what's actually in the files.)
(I see now in one of the threads I've linked, the Mephisto HDCD is mentioned specifically as using lots of dynamic range expansion.)
I suppose one justification for calling HDCD "dead" is that Charlie Hanson himself did, in the above linked thread. He commented that since HDCD is not on the feature list of the "latest Oppo player", we can say officially it is dead. (People love to call things they disparage dead. They shouldn't. Dead doesn't mean "not growing.")
Weirdly and sadly Charlie Hanson, a highly touted High End audio designer who created good sounding but high priced and needlessly high distortion CD players and amplifiers, himself died not long after writing those words. I did like one thing he did--a very good technical denunciation of SACD, wait a minute, maybe I could question some of his assertions on that one a little more now too. I remember very much liking his linear filter when he first described it, but when I saw the measurements in Stereophile I was not impressed...another leaky "linear phase" filter with non-negligible distortion. I was actually reading this HDCD column at Hydrogen Audio just and before his death. I was about the same time considering getting the Pono which he designed--and thinking that to be a plus. But it could not have worked out as well for me as my Oppo BDP 205, which I didn't realize was going to be a great streamer in combination with Roon. Pono does not support Roon as far as I can tell, it doesn't function as a digital output streamer, and it doesn't play any kinds of discs. The high res service didn't go very far then, but now with Qobuz it does, on any Roon device.)
HDCD lives on at my home in many titles, with excellent decoding.
But maybe it could be better still...either if preconverted to 24 bit (to avoid a needless DA/AD conversion which I believe essentially harmless because done at 24 bits) or, an even better HDCD decoder actually using the TF flag if, as some claim, existing units don't?
(*Test: Resample the output of an HDCD DAC with the TF in the material, or with the TF expunged from the material, and show they have the same HF spectrum and transients. Or written words by the original owners and engineers of PMI, such as Keith Johnson.) It's the TF that should restore some of the 88kHz sampling rate quality, with sharper transients and so on.
I had known that Microsoft had purchased PMI for the IP, which many are claiming as licensing fees on the many HDCD discs, but I had also previously heard Microsoft wanted the HDMI patents regarding sticking extra code bits in an audio stream, for other purposes.
Anyway, I would think all these patents, the Meitner and HDCD patents, have all expired. What's left are trade secrets we may never know for sure. But what is patented is public knowledge.
While true high resolution negates the need for quasi high resolution systems like HDCD, a compatible CD quality format (or streaming!) format with standard (dynamically compressed) and audiophile (uncompresed) still might be an excellent idea if it could end the Loudness Wars, at least for people who care.
On Hanson, notice how he asserts here that:
When the ultimate value is mapped back to 24 fixed bits, then you may lose precision, because only 24 bits are available. At that point, if you have reduced the magnitude by 8 bits below maximum, you still have 16 bits of resolution left, and if that was what you have started with, in principle you have lost nothing.
The actual penalty in this illustration is only paid in the ultimate conversion, which lacks true 24 bit resolution. But it may have close-to-24-bits "resolution" whatever than means, it's just not distortion or noise free. And, besides, the lack of distortion and noise isn't very important at levels that low.
And then he goes on to claim DSD starts with only 1 bit and therefore 6dB of dynamic range. That is true at the DSD sampling rate only. At musical frequencies of interest, there is already far more dynamic range. Though it is native dynamic range falls below the 16bit equivalent at some midrange frequency. But once again that's far more complicated than his simplistic brush here.
Then he makes an outrageous claim that dither is inferior to rounding, a slap in the face of thousands of engineers and decades of digital audio engineering. And then that nothing doesn't make a difference, including the purity of the copper.
If Charlie Hanson is the ultimate source of the claim that the HDCD Transient Filter feature is nowhere supported, even on PMI (which he calls PM) chips, and players designed prior to the Microsoft purchase of HDCD (like my Denon DVD-9000), I wouldn't find it convincing at all. However, I would not be surprised if it were true of players designed AFTER the Microsoft purchase of HDCD, as they had no particular interest in HDCD itself, as has been obvious by their actions.
One thing is clear, my DVD-9000 does respond with about 6dB higher potential output on HDCD discs than CD discs. Later players do not do this, as apparently Microsoft backed down on making that an HDCD requirement.
And, yet, the DVD-9000 does not actually have a PMI chip. I believe it has the equivalent of the PMI 200, which was (as far as I have been able to determine) not an actual chip, but a design specifiiation, that included the 6dB higher potential level, and possibly an implementation of the Transient Filter changes, because this was a unique "reference" implementation.
Update: Despite all the claims by Charlie Hanson and a few other individuals who had no direct working knowledge (Charlie claims he talked to one of the designers at "PM", which he always misnames (it was PMI), and not naming anyone) that there was not switchable Transient Filter on playback, it appears that none other than Christopher Key, the author of HDCD.exe, and very knowledgable about all things HDCD, apparently did think there was, at least in 2007, in this blog (which ironically was linked by the HDCD wiki denying that Transient Filters, by bdo, who I now worship for implementing ffmpeg's HDCD, even if he wrote a disparaging and incorrect wiki about it).
Christopher Key went so far as to prepare two files, one with an impulse train, and one with a high frequency sweep 10kHz-22kHz, and asked anyone to try it with their hardware decoder. This was after discussing several papers about the filters that (might) be used. (This was not a nothing...there were at least papers written about it.)
Sadly, look for yourself, I don't see any evidence in the above discussion that anyone actually did the test the Christopher Key was asking for. This is exactly what I want right now to test, that perfect, instead of trying to ferret out the effect in actual music. Unfortunately the files do not appear anymore to be downloadable. I have messaged Christopher Key.
One way or another, CD's using HDCD encoding should best be decoded with HDCD. This, from the beginning, was the biggest complaint. It's not "truly" compatible. But the same limitation may apply to nearly everything "compatible," and then there are lots of things like DVD-Audio which are not compatible.
Nowadays I play back HDCD's on my Denon DVD-9000, which is one of the best HDCD players ever. It has the second generation HDCD decoder...but it's not an actual HDCD chip. It's embedded in the firmware, which also includes AL24, Denon's upconverting oversampling system. Along with that, the DVD-9000 has dual differential Burr Brown 1704 Dacs, the best true PCM DAC chip ever made. After the 1704, everyone went to the cheaper Sigma Delta approach. 1704's continued to be used in Levinson and other high end DACs for awhile. The power supplies and build quality of the 40 pound DVD-9000 are beyond reproach, however the analog IC's could be better, though they are a notch above the preceding DVD-5000.
But, to make this work with digital crossovers and DSP, I must convert the analog output of the DVD-9000 to digital (using my Lavry AD10) in order to get the decoding. I convert the output to 24/96 high resolution digital so the HDCD decoding is fully captured.
Starting last year, I added a new way of "streaming" HDCD's from my library or music services. I put a dedicated Sonos Zoneplayer (a ZP80) sending PCM (with the HDCD bits if they happen to be there) to the digital input of my DVD-9000.
But sometime last year I borrowed that Sonos unit to serve as a second Sonos analog input in the kitchen. That never really worked for various reasons. The main reason for doing it was so that I could have a Sonos input dedicated to my Kenwood L-1000T tuner. But about the same time, I decided to switch to the slightly quieter and always pleasant sounding Sansui TU-D99X, the last TOTL tuner from Sansui featuring their custom made Walsh MPX decoder. It only has one output.
In over a year of "borrowing" the second ZP80 for the kitchen, I don't recall ever actually using it beyond the first test. Now I also have a 3-way switch feeding the main ZP80 in the kitchen, so I could send audio from the Mac, the Pioneer DVD recorder, or the tuner. It should not be necessary to send audio from the Oppo BDP-95 because it rides with the HDMI signal, which is sent to other rooms through a 4x4 matrix switch. I capture the audio from HDMI in the living room (as of last month) with a de-embedder, and I capture the audio from HDMI in the bedroom by digital optical from the TV to a DAC. The digital optical means that TV (and all it connects to) are electrically isolated from the stereo to prevent hum.
Re-installing the living room de-embedder enabled me to remove the second ZP80 from the kitchen and put it back into HDCD-streaming service in the Living Room, which I was happy to finally be able to do last night.
But one curious thing is that when using the DVD-9000 as an HDCD decoder and DAC, it does not necessarily display the HDCD logo when a digital signal with HDCD is being decoded. In fact the last time around I never saw the HDCD logo light up, but I did tests to be sure (by testing dynamic range) that the HDCD decoding was actually being done. This is a quirk of the player that other people have commented about online. When playing HDCD discs, the light always comes on.
This time, I noticed something different. I noticed that while playing some titles, the HDCD light DOES come on. It comes on particularly for the Mannheim Steamroller Fresh Aire II HDCD. But on several HDCD's from Reference Recordings, which you'd think would be the most HDCD of all, it does not come on.
When using the player as a DAC, it seems the light is triggered only by the presence of certain HDCD features in the digital signal. It may indeed require the "dynamic range upward expansion" feature, in order for the light to come on. If the digital signal has only the variable digital filter feature, it's possible it does not come one.
And that may be why Reference Recordings tend not to make the light turn on. They might not use the upward expansion feature as much--precisely in order to be "more compatible."
For titles in which the HDCD light comes on, it comes on identically for using both the Sonos controlling software, and Roon. Both Sonos and Roon are leaving the bits alone.
I believe I've seen as much as 3dB dynamic range expansion with HDCD's. Last night I measured 2dB expansion from Fresh Aire II. Unlike some later players, the Denon DVD-9000 actually puts out more signal voltage when the dynamic range expansion is occurring, up to 3.5V RMS or so. A friend of mine complained about this in 1990, and panned HDCD players as a result. Later players simply play HDCD's at a softer level to allow the peak expansion to occur. You can imagine that helped "kill" the format as discs seemed to play softer on average, and louder always sells better.
Hydrogen Audio has a good, though slanted, overview of the HDCD format. Their view is mostly derogatory, but their technical information is mostly excellent and otherwise hard to get. It's hard to read this without seeing how they're trying to get in a dig whenever they can, such as by first mentioning Microsoft as the Owner instead of the original inventor and owner, and then, when they finally get around to mentioning the famous inventor, they misname them "Pacific Microsonic" (PM) instead of "Pacific Microsonics Inc. (PMI). If someone doesn't even bother to pronounce or spell your name correctly, it's pretty much a giveaway that they are disparaging you. And then, what exactly does it mean to call a format "dead." A factual but non-derogatory description would simply be that new titles and hardware are not beling released. (For the folks at Hydrogen Audio, even claiming that anything is audibly better than CD format is basically forbidden.)
The HDCD wikipage at Hydrogen Audio alleges to echo the late Charlie Hanson (a competitor having his own slow and leaky "linear phase filter") in claiming that HDCD could not use variable playback filters because of a Meitner patent. I'm not sure if this story is 100% true. If you take the time to read Hanson's original comments at Hydrogen Audio, he nevertheless recommends using a hardware decoder (as I am doing) as "the gold standard" because of the fully correct implementation of dynamic range expansion. I spoke to Reference Recording people around 2010, and that is exactly what they recommended, and they also agreed with my approach of analog sampling the output of an HDCD decoder in high resolution digital for downstream DSP processing. Using Foobar or HDCD.exe to do the dynamic range decoding is known not to be as accurate (or at least claimed, by Charlie Hanson, others dispute this).
I have not seen a fully convincing debunking of the claimed transient filter selection anywhere. Along with Hanson, there are small number of audio objectivist cranks (who don't believe high resolution is needed either) say it was never used because of the Meitner patent. But they don't actually show any proof that HDCD players don't use the transient filter selection feature or link to verifiable information.* Meanwhile, there are numerous text and graphs show the effects of the dynamic range expansion, which is relatively easy to implement in conversion software (but apparently not always perfectly).
In this long thread about HDCD at Steve Hoffman's site, there is only one commenter, Jedi Joker, denying the utility of the transient filter function.
The "TF" flag is meaningless on playback. Why it is encoded into the HDCD signal remains somewhat of a mystery. The transient filters do not exist on the PMD100 and PMD200 decoder chips that were used in playback gear, nor do they exist in current HDCD-capable playback solutions utilizing alternate decoding methods, but only on the Model One and Model Two ADDA converters. The filters are engaged on the A/D side during recording, meaning whatever effect they have is digitized as audio into the resulting files. For whatever reason, a flag is simultaneously encoded into the HDCD bit, but has no effect on playback in any playerSo, are we going to the words of the Jedi Joker as the final words? I'm still trying to verify this. The post on HDCD at Hydrogen Audio extends to 40 pages! Here's another discussion of HDCD at Roon, and a poster who calls himself Andrew J Shepherd reiterates the claim that the Transient Filter is not implemented in any hardware device. At least we can see Andrew J Shepherd as a real person with apparently solid engineering background, whose main interest seems to be telecommunications. But where did he get his information on this?
HDCD might have been very very useful...if it had been used like this: a single CD has two versions, the undecoded version with little dynamic range (like all standard CD's these days) and the HDCD decoded version with much more dynamic range, for those who demand it. That kind of feature is offered nowhere other than HDCD as far as I know.
The transient filter sounds like a very good idea also. That might capture 50% of the benefit of 88.2kHz sampling rate above 44.1, if in fact it were implemented. That Meitner--an early supporter of Sony's SACD project--would block full implementation of HDCD is dastardly. My only experience with a Meitner product was at a hifi society store demo where the Meitner amplifer society members wanted to hear burned out driving Apogee speakers.
And there are some very good sounding HDCD's. That's why it's worth having some kind of HDCD decoding. One of these is the Reference Recordings Mephisto and Company. Without decoding, it sounds very good. With decoding, it's a one of a kind sonic knockout. Most other HDCD's show similar differences with and without decoding. So for me it's worth having HDCD decode capability, even if it was somewhat of a scam in the beginning. (And strangely, Mephisto and Company does NOT light the HDCD light on my Denon while streaming. And yet it appears to have the maximum amount of HDCD expansion, approaching 6dB peak expansion, while the Mannheim Steamroller discs do light the light, with only about 3dB expansion. I suppose I should get one of the HDCD exploration tools mentioned in the threads above to see what's actually in the files.)
(I see now in one of the threads I've linked, the Mephisto HDCD is mentioned specifically as using lots of dynamic range expansion.)
I suppose one justification for calling HDCD "dead" is that Charlie Hanson himself did, in the above linked thread. He commented that since HDCD is not on the feature list of the "latest Oppo player", we can say officially it is dead. (People love to call things they disparage dead. They shouldn't. Dead doesn't mean "not growing.")
Weirdly and sadly Charlie Hanson, a highly touted High End audio designer who created good sounding but high priced and needlessly high distortion CD players and amplifiers, himself died not long after writing those words. I did like one thing he did--a very good technical denunciation of SACD, wait a minute, maybe I could question some of his assertions on that one a little more now too. I remember very much liking his linear filter when he first described it, but when I saw the measurements in Stereophile I was not impressed...another leaky "linear phase" filter with non-negligible distortion. I was actually reading this HDCD column at Hydrogen Audio just and before his death. I was about the same time considering getting the Pono which he designed--and thinking that to be a plus. But it could not have worked out as well for me as my Oppo BDP 205, which I didn't realize was going to be a great streamer in combination with Roon. Pono does not support Roon as far as I can tell, it doesn't function as a digital output streamer, and it doesn't play any kinds of discs. The high res service didn't go very far then, but now with Qobuz it does, on any Roon device.)
HDCD lives on at my home in many titles, with excellent decoding.
But maybe it could be better still...either if preconverted to 24 bit (to avoid a needless DA/AD conversion which I believe essentially harmless because done at 24 bits) or, an even better HDCD decoder actually using the TF flag if, as some claim, existing units don't?
(*Test: Resample the output of an HDCD DAC with the TF in the material, or with the TF expunged from the material, and show they have the same HF spectrum and transients. Or written words by the original owners and engineers of PMI, such as Keith Johnson.) It's the TF that should restore some of the 88kHz sampling rate quality, with sharper transients and so on.
I had known that Microsoft had purchased PMI for the IP, which many are claiming as licensing fees on the many HDCD discs, but I had also previously heard Microsoft wanted the HDMI patents regarding sticking extra code bits in an audio stream, for other purposes.
Anyway, I would think all these patents, the Meitner and HDCD patents, have all expired. What's left are trade secrets we may never know for sure. But what is patented is public knowledge.
While true high resolution negates the need for quasi high resolution systems like HDCD, a compatible CD quality format (or streaming!) format with standard (dynamically compressed) and audiophile (uncompresed) still might be an excellent idea if it could end the Loudness Wars, at least for people who care.
On Hanson, notice how he asserts here that:
1) Computer-based digital volume controls work with 32-bit floating point operations. These only have 24 bits of precision, as the rest is in the exponent. When you turn your volume down by (say) -48 dB, you are literally throwing away 8 bits of resolution. If you are starting with 16-bit data (99.9% of all music files), you are only left listening to 8 bits of resolution. Not good.First, the meaning of floating point is that when you lower the magnitude, the exponent changes. Within the 32 bit domain, you are not losing any resolution! So this is error #1. The fact that floating point is used does not make the difference he is describing, in fact, exactly the reverse
When the ultimate value is mapped back to 24 fixed bits, then you may lose precision, because only 24 bits are available. At that point, if you have reduced the magnitude by 8 bits below maximum, you still have 16 bits of resolution left, and if that was what you have started with, in principle you have lost nothing.
The actual penalty in this illustration is only paid in the ultimate conversion, which lacks true 24 bit resolution. But it may have close-to-24-bits "resolution" whatever than means, it's just not distortion or noise free. And, besides, the lack of distortion and noise isn't very important at levels that low.
And then he goes on to claim DSD starts with only 1 bit and therefore 6dB of dynamic range. That is true at the DSD sampling rate only. At musical frequencies of interest, there is already far more dynamic range. Though it is native dynamic range falls below the 16bit equivalent at some midrange frequency. But once again that's far more complicated than his simplistic brush here.
Then he makes an outrageous claim that dither is inferior to rounding, a slap in the face of thousands of engineers and decades of digital audio engineering. And then that nothing doesn't make a difference, including the purity of the copper.
If Charlie Hanson is the ultimate source of the claim that the HDCD Transient Filter feature is nowhere supported, even on PMI (which he calls PM) chips, and players designed prior to the Microsoft purchase of HDCD (like my Denon DVD-9000), I wouldn't find it convincing at all. However, I would not be surprised if it were true of players designed AFTER the Microsoft purchase of HDCD, as they had no particular interest in HDCD itself, as has been obvious by their actions.
One thing is clear, my DVD-9000 does respond with about 6dB higher potential output on HDCD discs than CD discs. Later players do not do this, as apparently Microsoft backed down on making that an HDCD requirement.
And, yet, the DVD-9000 does not actually have a PMI chip. I believe it has the equivalent of the PMI 200, which was (as far as I have been able to determine) not an actual chip, but a design specifiiation, that included the 6dB higher potential level, and possibly an implementation of the Transient Filter changes, because this was a unique "reference" implementation.
Update: Despite all the claims by Charlie Hanson and a few other individuals who had no direct working knowledge (Charlie claims he talked to one of the designers at "PM", which he always misnames (it was PMI), and not naming anyone) that there was not switchable Transient Filter on playback, it appears that none other than Christopher Key, the author of HDCD.exe, and very knowledgable about all things HDCD, apparently did think there was, at least in 2007, in this blog (which ironically was linked by the HDCD wiki denying that Transient Filters, by bdo, who I now worship for implementing ffmpeg's HDCD, even if he wrote a disparaging and incorrect wiki about it).
Christopher Key went so far as to prepare two files, one with an impulse train, and one with a high frequency sweep 10kHz-22kHz, and asked anyone to try it with their hardware decoder. This was after discussing several papers about the filters that (might) be used. (This was not a nothing...there were at least papers written about it.)
Sadly, look for yourself, I don't see any evidence in the above discussion that anyone actually did the test the Christopher Key was asking for. This is exactly what I want right now to test, that perfect, instead of trying to ferret out the effect in actual music. Unfortunately the files do not appear anymore to be downloadable. I have messaged Christopher Key.
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