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Topic: HDCD Decoder (Read 329646 times) previous topic - next topic
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HDCD Decoder

Reply #175 –
The HDCD decoder filter always outputs 20 bits precision. It is up to the user to set their output device to 24 bits or greater for playback. Or, if using the HDCD decoder when transcoding to another format, it's up to the user to transcode to a 24 bit format or greater, or some lossy format that accepts 24 bit or floating point sample data.

This is meaningless for portable players, since most of them only have 16 bit DACs anyway.

HDCD Decoder

Reply #176 –
Quote from: kode54 on
The HDCD decoder filter always outputs 20 bits precision. It is up to the user to set their output device to 24 bits or greater for playback. Or, if using the HDCD decoder when transcoding to another format, it's up to the user to transcode to a 24 bit format or greater, or some lossy format that accepts 24 bit or floating point sample data.

This is meaningless for portable players, since most of them only have 16 bit DACs anyway.



thanks

Has there been any progress on adding transient filtering,  my understanding is the oversample filter used is only 2x,  so most computers could handle 88.2khz.

HDCD Decoder

Reply #177 –
Quote from: kode54 on
The HDCD decoder filter always outputs 20 bits precision. It is up to the user to set their output device to 24 bits or greater for playback. Or, if using the HDCD decoder when transcoding to another format, it's up to the user to transcode to a 24 bit format or greater, or some lossy format that accepts 24 bit or floating point sample data.

This is meaningless for portable players, since most of them only have 16 bit DACs anyway.


I'm aware of that but what I meant was, if the file was played from a 16 bit DAP, would the file be played without problems?

HDCD Decoder

Reply #178 –
Quote from: d_headshot on
Quote from: kode54 on
The HDCD decoder filter always outputs 20 bits precision. It is up to the user to set their output device to 24 bits or greater for playback. Or, if using the HDCD decoder when transcoding to another format, it's up to the user to transcode to a 24 bit format or greater, or some lossy format that accepts 24 bit or floating point sample data.

This is meaningless for portable players, since most of them only have 16 bit DACs anyway.


I'm aware of that but what I meant was, if the file was played from a 16 bit DAP, would the file be played without problems?



Not really a problem but it would be truncated to 16 bits without proper dithering,  of course out of a DAP where absolute SQ is not really an goal I don't think there is an issue.

HDCD Decoder

Reply #179 –
Quote from: Glenda on
Has there been any progress on adding transient filtering,  my understanding is the oversample filter used is only 2x,  so most computers could handle 88.2khz.


"Transient Filtering" is a giant misunderstanding, created by the false advertising of Pacific Microsonics. They had brilliant engineers working for them, but sleazy marketing people.

The Pacific Microsonics (PM) D/A converter used two different anti-aliasing filters during the conversion to digital, depending on the spectral content and loudness of the signal. For some reason the choice of filters is encoded in the "hidden subcode" that triggers the correct decoding upon playback.

But there never has been two different playback digital reconstruction filters -- only one.

People were misled both by the ambiguous text of the HDCD literature and also by the fact that the "subcode" showed which filter was used during recording. So you do not have to worry about this. Not one little bit.

Another place where PM"s marketing team created a lot of (deliberate) confusion is that there are only two features that require decoding -- Peak Extend (PE) and Low-Level Extension (LLE). But these can be turned on or off by the mastering engineer. Many albums have been recorded with both of these features turned off. So there is nothing to decode.

But the "HDCD" light will still turn on, because this A/D converter always inserts the "subcode", whether or not it is needed. Another sleazy trick from the PM marketing department. (This is why there are so many discs with no HDCD logo on the cover, but that light up the "HDCD" light.)

Other instances where decoding is not needed include almost all usage of LLE. LLE does not activate until the signal level drops below -45 dBFS. With popular music, this pretty much happens only in the silence between tracks. You might see a second or two of activity as the song fades out, but that is it. With classical music, it is used a little bit more but still not much. I looked the the Reference Recordings album "Nojima Plays Ravel" and there were a few cases where there were very quiet passages that would trigger a dB or two of LLE for perhaps five or ten seconds.

Then there is PE. This doesn't start to do anything until the peak level reaches -9 dBFS. Many of Joni Mitchell's albums were remastered using HDCD. About half of them stay below -9 dBFS for pretty much the entire album and thereby gain no benefit from HDCD decoding. The other half do have peaks above -9 dBFS and will have some benefit. But to achieve the full benefit requires a really good stereo system. HDCD cannot make the peaks any louder, as digital has a hard limit. So what it does is keep the peaks loud and reduce the rest of the music by -6 dB in level. This also means that your Signal/Noise ratio will be reduced -6 dB. So you don't really want to do this unless you have a great system with a very low noise floor to begin with.

Finally, the engineer who designed the PM A/D converter, Keith Johnson, is a brilliant engineer. Even though the machine has been discontinued for at least 6 years, it is still one of the best sounding A/D converters ever made. So discs where the "HDCD" light lights up mean that the album is likely to sound exceptional, whether or not any of the actual HDCD features were engaged by the mastering engineer. The high sound quality of "HDCD" discs is due far more to the great A/D converter and far less to the "HDCD" features.

HDCD Decoder

Reply #180 –
Quote from: Charles Hansen on
Finally, the engineer who designed the PM A/D converter, Keith Johnson, is a brilliant engineer. Even though the machine has been discontinued for at least 6 years, it is still one of the best sounding A/D converters ever made.

Do you have any test data that supports this claim which is compliant with our Terms of Service?

HDCD Decoder

Reply #181 –
Quote from: greynol on
Quote from: Charles Hansen on
Finally, the engineer who designed the PM A/D converter, Keith Johnson, is a brilliant engineer. Even though the machine has been discontinued for at least 6 years, it is still one of the best sounding A/D converters ever made.

Do you have any test data that supports this claim which is compliant with our Terms of Service?


I presume you mean:

"8. All members that put forth a statement concerning subjective sound quality, must -- to the best of their ability -- provide objective support for their claims. Acceptable means of support are double blind listening tests (ABX or ABC/HR) demonstrating that the member can discern a difference perceptually, together with a test sample to allow others to reproduce their findings. Graphs, non-blind listening tests, waveform difference comparisons, and so on, are not acceptable means of providing support."

I am unaware of any ABX testing of A/D converters.

Every single mastering engineer in the industry chooses the equipment that sounds best to them (or occasionally chooses on the basis of its reputation of how it sounds to others), and none choose on the basis of ABX testing. Since no such ABX evidence exists I would assert that I have provided objective support to the best of my ability.

But you are the moderator. It is your forum. If you want to edit or delete my post, that is your decision.

Happy New Year!

HDCD Decoder

Reply #183 –
Quote from: greynol on
I just wanted you to be aware of our rules and know that we have an expectation that they be followed.

Happy New Year to you as well!


I'll edit the original post. Let me know if you find it acceptable.

EDIT: OOPS! I can't edit it... I guess it's too old....

HDCD Decoder

Reply #185 –
Quote from: Charles Hansen on
Quote from: Glenda on
Has there been any progress on adding transient filtering,  my understanding is the oversample filter used is only 2x,  so most computers could handle 88.2khz.


"Transient Filtering" is a giant misunderstanding, created by the false advertising of Pacific Microsonics. They had brilliant engineers working for them, but sleazy marketing people.

The Pacific Microsonics (PM) D/A converter used two different anti-aliasing filters during the conversion to digital, depending on the spectral content and loudness of the signal. For some reason the choice of filters is encoded in the "hidden subcode" that triggers the correct decoding upon playback.



Some folks playing with hardware HDCD decoder came to the same conclusion:  HDCD hardware

However I am also baffled by the fact that the inventor of hdcd.exe found the code for transient filtering (beyond the in use flag) in the HDCD's and was going to try and match it with an impulse analysis but abandonded the project when he realized he that he couldn't access the internal 2fs output of the hdcd decoder inside the pmd100.

HDCD Decoder

Reply #186 –
Quote from: Glenda on
However I am also baffled by the fact that the inventor of hdcd.exe found the code for transient filtering (beyond the in use flag) in the HDCD's and was going to try and match it with an impulse analysis but abandonded the project when he realized he that he couldn't access the internal 2fs output of the hdcd decoder inside the pmd100.


The developer of the HDCD system also developed the PMD-100 HDCD decoder / digital filter IC. There is no problem to access the 2 Fs output of the decoder. But that wouldn't help, as there is only one digital reconstruction filter inside the chip. So that was not the issue.

The system seems to work well enough with just one playback filter. So the real question is why did they include the flag for which filter was used during the recording process?

All we can do is speculate. There are a few things that we know. One is that they were tinkering with the system a bit. The first HDCD releases used a prototype encoder. That encoder had a shorter hidden subcode. Apparently they got some false positives (whereby the system would be triggered by musical passages), because the production system had a longer code that was essentially immune to false triggering.

Another thing we know is that silicon resources were much more limited in 1994 than they are today. The digital filter in the PMD-100 is not a half-band type (as is normally used in almost all digital products) and therefore requires double the number of taps. This means double the number of coefficients in ROM and twice as many hardware MACs. This was all "expensive" from a real-estate standpoint back then and they may not have had the space to fit it all in the part with another filter also.

The other thing is that I don't think that Pacific Microsonics was all that well funded. So it may have just been a question of insufficient funds to do what they really wanted. For example, the PMD-100 was made on a 0.6 micron process. The fab that was making the part shut that line down around 2002 and it would have cost close to $500,000 to make another version of the same part. Apparently they didn't have the money because the PMD-200 was just a Motorola DSP with a special ROM program burned into it. The '200 added support for higher sample rates, but not for two different playback filters. If they ever had a plan for implementing two playback filters, that would have been the time. But they must have been running out of money because Microsoft bought PM before the '200 was even put into full production. Judging from what MS has done with HDCD, I don't think they paid a lot for it. I would guess that the founders were glad to get out of it with something (rather than nothing).

As noted before, Keith Johnson is one of the top engineers in audio, and he did an outstanding job on the Model One and Model Two A/D converters. The power supplies, clocks, audio circuitry, and converters themselves were far more advanced than what others were doing in 1994, or even in 2004 for that matter. (I hope that statement is within the guidelines!) Used units still fetch top dollar today. In fact there is a used Model Two on Audiogon right now. The asking price is $20,000, which was the original list price. Many mastering engineers were able to purchase them new for half that price.

HDCD Decoder

Reply #187 –
Quote from: Charles Hansen on
The power supplies, clocks, audio circuitry, and converters themselves were far more advanced than what others were doing in 1994, or even in 2004 for that matter. (I hope that statement is within the guidelines!)

Yes this is within the guidelines.  Had you said this hardware offered better sound quality then you would be obligated to provide objective evidence in the way of DBT results.

HDCD Decoder

Reply #188 –
Very informative post Mr Hansen.  Thankyou .

HDCD Decoder

Reply #189 –
I have installed the HDCD foobar2000 add-on. But when I play a HDCD file, in the console doesn't say that file is recognized as HDCD. But, if I "scan" for HDCD tracks the utility reports that finds the HDCD tracks.
Is this normal?

HDCD Decoder

Reply #190 –
As indicated in the original post, the HDCD status is indicated by dynamic file info fields, which you may retrieve with %__hdcd% or $info(hdcd) in your status bar or other dynamically updated title formatting scripts.

HDCD Decoder

Reply #191 –
Maybe you can add a tutorial on the foobar add-on documentation page. Just for people like me
Thanks for the app! I have four players capable of HDCD decoding (one from SPDIF), foobar decoding is from FLAC files on PC (WMP can do it only from optical medium).

HDCD Decoder

Reply #192 –
I did it... thank you.
Looks nice like below - shows (HDCD) when plays HDCD and nothing for the rest:
Code: [Select]
$if($info(hdcd),'(HDCD)',)

HDCD Decoder

Reply #193 –
All the info "out":
Code: [Select]
 $if($info(hdcd),'(HDCD:',) $if($info(hdcd_gain),Gain= $info(hdcd_gain) Peak extend=$info(hdcd_peak_extend) Transient Filter=$info(hdcd_transient_filter)')',)

Awesome info! Exemples:

Yes - 90125 : Gain= 0dB Peak extend= no Transient filter= yes/no (varies quickly)
Mike Oldfield - Five Miles out :  Gain= 0dB Peak extend= yes Transient filter= no
Mike Oldfield - Islands :  Gain= 0dB Peak extend= no Transient filter= no
Roxy Music - Avalon :  Gain= 0dB Peak extend= no Transient filter= no
Shana Morrison - Caledonia : Gain= 0dB Peak extend= yes Transient filter= no
The Beach Boys - Surfin' Safary : Gain= 0dB Peak extend= no Transient filter= no
Joe Walsh - The Smoker You Drink : Gain= 0dB Peak extend= no Transient filter= yes/no (varies quickly)

HDCD Decoder

Reply #194 –
Sorry, in Version 1.10 I don't found the advanced preferences option under the Decoding from HDCD decoding.

HDCD Decoder

Reply #195 –
@kode54
Could you tell us a bit about the mechanism used when "Don't half volume" is ticked? Are you applying gain, maybe?

HDCD Decoder

Reply #196 –
Quote from: -Richy- on
Sorry, in Version 1.10 I don't found the advanced preferences option under the Decoding from HDCD decoding.


Look again, it's there. (Advanced > Decoding > HDCD Decoder)
Quote from: Sandrine on
@kode54
Could you tell us a bit about the mechanism used when "Don't half volume" is ticked? Are you applying gain, maybe?

Yeah, kode54, where's my bits at? ;);)

HDCD Decoder

Reply #197 –
My HDCD players have in the output stage a +6dB selective amplifier. When a HDCD signal is detected, that activate the +6dB gain...
6dB means double/half of the output voltage.

HDCD Decoder

Reply #198 –
HDCD decoding effectively halves the volume, reducing the output by 6dB. This isn't a problem if peak extension is enabled, but if not, then your output will always be half as loud if HDCD information is found.

Enabling that option doubles the volume of decoded HDCD output, which is fine when peak extension is not used, but when it is, peaks can reach as high as 2.0.

Enabling it or not doesn't really matter if you use ReplayGain on the resulting tracks with this component installed.

HDCD Decoder

Reply #199 –
I didn't measured by now, but I might open one of my players to test it - to see if the HDCD's with "peak extend" activate that +6dB analog stage or no. Now, that I know which HDCD's have that active.