In article ,
froggy wrote:
Le 18/06/12 17:23, Jim Lesurf a écrit :
(snip)

Not much of an engineer unfortunately, but does this help?

http://www.foobar2000.org/components/view/foo_hdcd

Thanks for that! :-)

The item on the page you pointed to is a Windows dll. So in itself not much
use to me. *But* it did also let me find the source code (in C and C++)
from the main foobar site. That may be very useful. :-)) The discussion is
also interesting as it seems to confirm some of my doubts about some
aspects of HDCD.

Thanks again,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
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Audio Misc http://www.audiomisc.co.uk/index.html

"Jim Lesurf" wrote in message
...
In article m, Rob
reply@ng wrote:
On 18/06/2012 11:05, Jim Lesurf wrote:

snip

In this case the general result on a *non* HDCD player is to squash any
peaks, distort sustained loud sounds, and lift the quieter parts by about
6dB. i.e. pretty much like the kind of idiotic 'loudness' treatments
inflicted by those obsessed with 'louder is better'.


Snip

Hi Jim - very interesting reply to Rob. The bit that specifically stood out
is the bit I've left quoted above. My understanding - admitedly based only
on a handful of Telarc SACD's, is that there are two layers on the CD. One
for conventional players and one that only HDCD players can find....

The blurb sheet of Telarc SACD 60516...has a diagram showing two layers on
the CD, one DSD which has both 2 channel and 5.1 and a conventional CD layer
conforming to the original CD standard for dynamic range etc.

are these Telarc discs not what you mean by HDCD?

Dave

In article , Dave C
wrote:

"Jim Lesurf" wrote in message
...
In article m, Rob
reply@ng wrote:
On 18/06/2012 11:05, Jim Lesurf wrote:

snip

In this case the general result on a *non* HDCD player is to squash
any peaks, distort sustained loud sounds, and lift the quieter parts
by about 6dB. i.e. pretty much like the kind of idiotic 'loudness'
treatments inflicted by those obsessed with 'louder is better'.


Snip

Hi Jim - very interesting reply to Rob. The bit that specifically stood
out is the bit I've left quoted above. My understanding - admitedly
based only on a handful of Telarc SACD's, is that there are two layers
on the CD. One for conventional players and one that only HDCD players
can find....

The blurb sheet of Telarc SACD 60516...has a diagram showing two layers
on the CD, one DSD which has both 2 channel and 5.1 and a conventional
CD layer conforming to the original CD standard for dynamic range etc.

are these Telarc discs not what you mean by HDCD?

Yes and no, m'lud. :-)

If they are like the few 'Linn Records' SACD/HDCD hybrids I have then the
'CD layer' is certainly playable on a normal audio CD player. One of the
points of HDCD is that it is *claimed* to be 'compatible' with audio CD
players and will thus play in them. But it may also be HDCD as outlined
below.

To some extent here, the problem is to clarify the wording and distingush
the 'container' from the 'contained'.

I have a few HDCD discs that were sold to me as 'audio CDs' and have a
single layer. They play on normal audio CD players but are HDCD branded,
etc.

I also have a few hybrid discs. These have a 'DVD layer' and a 'CD layer'.
With the DVD (physical) layer containing SACD format DSD data and the CD
(physical) layer containing 'red book' audio CD. No HDCD involved. (e.g.
the new EMI 'Signature' series which I quite like.)

I also have a few hybrid discs with the 'DVD layer' containing SACD/DSD,
but the 'CD layer' containing HDCD format data samples in the 'red book'
format for an audio CD. (e.g. some Linn records discs.)

So we have:

1) Physical layers. A disc may just have one, or may have two. One may be
'DVD' and another may be 'CD'. These can be used for almost anything within
the normal specs for a 'CD' or 'DVD' inc data, video, etc.

2) SACD is a proprietary format for 'filing' the data on a DVD, devoted to
audio in the 'DSD' 1-bit format. The point being to make the data hard to
rip, so far as I can tell. If it were a normal DVD it would have a normal
DVD filter root and could be seen on a computer.

3) HDCD is a tweak to 'audio CD' that changes how the player should
understand and render the samples. But only an HDCD player or decoder can
do this. A normal audio player will play out assuming linear PCM samples.

One of the aims of HDCD is that to a normal CD player it looks just like an
ordinary audio CD. But the sample values have been mucked about in a way a
CD player doesn't notice. They aren't all LPCM any more.

So it should play 'normally' sic. The caveat is that if it has been 'soft
limited' then the result is - on a normal CD player - distorted by having
the sound squashed out of shape for some 'loud' parts. This is because the
CD player doesn't know how to undo the soft compression that HDCD can apply
to get itself a wider dynamic range.

But some players may be confused by a dual layer hybrid because they expect
a single CD layer. That's a physical/optical problem due to the presence of
two physical layers on the disc that scatter/reflect light.

In principle, HDCD encoded data can be used for other formats like Wave
files, etc. But so far as I know, no-one commercially does that.

On top of all that, some discs may be 'copy protected' (or not). Since the
demise of the old Red Book patent cover people can see such discs as if an
audio CD provided they avoid the copyrighted logos, etc. So the result may
play on a normal audio CD player (it should), albeit destorted in places,
but might not rip on a computer as its TOC has been mucked about. However
such copy protection isn't a part of HDCD as such.

HDCD is nominally obsolete in a world of high rez computer files, DVDs that
can carry them, etc. But both HDCD and SACD persist for reasons that are
more to do with commercial control and PR than music, I'd say.

Isn't it nice when the 'media biz' keep it nice and simple for us all?...
8-}

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

On 19/06/2012 10:14, Jim Lesurf wrote:
In aweb.com, Rob
reply@ng wrote:
On 18/06/2012 11:05, Jim Lesurf wrote:

[snip]

What insofar as you can tell is the thinking behind HDCD - the
assumptions about say CD that it tries to redress?

Well, according to the Patent and the other info the creators have written
that I've read, their argument is as follows.

That Audio CD is limited in both

A) Dynamic range.

B) Bandwidth.

The argument for (A) is that we know people can - in fairly ideal
situations - 'hear' a range of sound levels covering about 120dB. From the
smallest sounds that can just be heard, up to the loudest that don't cause
pain or damage even on a short hearing. Whereas CD has a nominal range of
just over 90dB. So part of HDCD claims to be a menu of methods to 'expand'
the range of a CD.

This expansion is said it use two methods. One is to apply a nonlinear
curve to the max signal levels. In effect, squash the top 9dB or so into
3dB on a sample-by-sample basis. Bit like the old 'mu-law' and 'A-law'
nonlinear sampling of methods used in comms, etc, to get a wider range from
a limited number of bits per sample.

In this case the general result on a *non* HDCD player is to squash any
peaks, distort sustained loud sounds, and lift the quieter parts by about
6dB. i.e. pretty much like the kind of idiotic 'loudness' treatments
inflicted by those obsessed with 'louder is better'.

FWIW I have a feeling some people making CDs view HDCD as a sort of 'up
market' version of plain old 'make it louder to sell better' with the bonus
that some audio enthusiasts will be drawn by the label.

On a genuine HDCD player, the player knows the details of the nonlinearity
applied, and can expand it. Ideally, that removes the distortion and level
compression. So you can argue that the result is 'compression for the
masses, but a decent result for the elite who buy into HDCD'.

However that only gets you about 6dB greater range - at the cost of
distortion for non-users. i.e. just one more bit per sample. 17bits, not
the claimed 20.

For long 'quiet' passages HDCD is also said to gradually wind up the gain
level, moving the sound further above any noise of sample-level errors.
This should improve the range for long quiet passages. And data 'encoded'
in the LSB patterns tells an HDCD player how to correct this gain shift. So
correcting this adjustment as well.

That could provide the other (claimed) 13 bits per sample. i.e. if the gain
is wound up and down by up to 18dB during 'quiet parts' of the music.

The big *however* here is that pop/rock music hardly ever has passages like
those described in the HDCD info I've seen. This says that you need music
that stays below about -40dBFS for a long time for this to kick in. But
that isn't what most pop/rock/jazz is like.

And when I scan the pop/rock HDCDs I have, as yet I've not found the codes
or any sign of their spread in the LSB. (I'll keep looking, though.)

Of course, you can then point out that if we really need 120dB ranges then
we might not want to lose the LSB to use as a control channel. :-) The
documents claim we can't hear this. But if so, why do we need such a big
range? And how many domestic situations have any hope of hearing over a
120dB range? Most homes have a background noise of around 30dBA or more,
and won't welcome having to play out at 150dBA. 8-]

And of course essentially *all* the older HDCD rock/pop/jazz material that
has been remastered would have been recorded on systems with a range well
below 120dB anyway. You have to wonder what a 120dB range has to do with,
say, analogue Joni Mitchell tapes from the 1960s or 1970s.

In addition to all that, if you noise shape conventional LPCM CD you get an
audible available dynamic range that is somewhat higher than the basic 'bit
more than 90dB' value generally quoted by shifting quantisation noise to HF
where people don't hear low level noises so easily.

Now on to (B).

There the claims are fairly wooly. The argument is that the ADC and DAC
examine the incoming data and decide to adopt a given filter function from
a menu of options. For smooth music you might use a conventional time
symmetric filter. But for transient spikes you might go for a more 'join
the dots' one to avoid side ringing. This is then communicated to the DAC
via the LSB control channel.

The effect is said to be to let you mimic a system with a wider bandwidth
and make the result sound more like you'd been able to convey details above
22kHz. The snag is that a 'spikey' filter will alias in ways that the
decoder may not be truly able to correct as the information recorded
becomes ambiguous. (This isn't true for a filter that simply shifts the
ringing to after the peak. But what I've read doesn't seem to say this is
what HDCD uses.)

In some ways this is a bit like the 'spectral replication' trick in the
AAC+ (lossy) encoder which notes down how much HF was discarded and
makes a guess at what should replace it when the file is played.
(Essentially by assuming you put in 'harmonics' of the biggest tones in
what you kept.)

However I can't find any sign of this, or its control codes. So how much of
this is simply flim-flam I can't tell. At some point I'll look for excess
folded components near 22kHz as these would be symptoms of an attempt to
have a 'spiky' encode filter which tends to generate things at (22.05 - f)
kHz when fed an input at f kHz.

Hence the Patents, etc, make a number of sweeping claims about improved
dynamic range and bandwidth. But in practice I can't say that as yet I'm
confident that it does much more than give you an (optional) reversable
'soft limiting' to get about 6dB back.


Splendid, thanks very much for that. One to avoid if a normal CD player
isn't to hand, then.

In terms of method, it just seems like the wrong way of going about
things. If you want 'more' bandwidth and DR, just use a higher bitrate
recording and playback? HDCD might even mimic that quite well, I
suppose, and perhaps that's the point.

I'm also wondering about the thinking about human perception. Is this an
attempt to recreate the source, or create a sound that's more pleasant
and 'apparently' source-like. If the latter - what are the variables?
Techno-babble for one?!

Rob

On 22/06/2012 12:40, Jim Lesurf wrote:
snip/

2) SACD is a proprietary format for 'filing' the data on a DVD, devoted to
audio in the 'DSD' 1-bit format. The point being to make the data hard to
rip, so far as I can tell. If it were a normal DVD it would have a normal
DVD filter root and could be seen on a computer.


Bit more to it than that? -

http://en.wikipedia.org/wiki/Super_Audio_CD

That strikes me as the right way of doing things, if the recording
process is handled correctly.

Incidentally, if I had the time, I'd have a close look at the DBT and
other comparison tests mentioned on that wiki page. I find this
'measurement' of listening experiences highly suspect. Not sure why though!

/snip

Rob

In article m, Rob
reply@ng wrote:
On 19/06/2012 10:14, Jim Lesurf wrote:
In aweb.com, Rob
[big snip]

Splendid, thanks very much for that. One to avoid if a normal CD player
isn't to hand, then.

I'd say to be wary of buying an HDCD if you only have non-HDCD audio
players. Hard to say in advance what effect it has on any individual disc.

In terms of method, it just seems like the wrong way of going about
things. If you want 'more' bandwidth and DR, just use a higher bitrate
recording and playback?

Well, bear in mind that HDCD was invented in the first half of the 1990s.
So back then it may have seemed more sensible to try and 'improve' discs
that still played in Audio CD players than go for higher sample rates, etc,
for which no-one at the time had any domestic players in the field.

Nowdays it seems more like a gimmick used by some of those 'mastering' CDs.
Might be 'better' in some cases on an HDCD player, but at the cost of maybe
sounding *worse* than a well made plain old Audio CD.

However bear in mind the commercial side. It is a system owned by a given
company who can charge for its use and control who is allowed to make HDCD
material, etc. Combination of a revenue stream and "we have a feature our
competitors lack" for PR.

I'm also wondering about the thinking about human perception. Is this an
attempt to recreate the source, or create a sound that's more pleasant
and 'apparently' source-like. If the latter - what are the variables?
Techno-babble for one?!

Can't really comment on the stuff about switching the filtering. I've not
been able to find any clear and specific details of the filters, etc, used.
So I can't say if this ever is done or is flim-flam. I continue to poke
into this, though.

FWIW I've made a bit of progress with understanding the foobar source code.
But am still some way from really making sense of it. I have, however,
asked someone I know who is a much better programmer if he can help me
make sense of the code. I'm explaining the audio side and he knows vastly
more than me about C/C++. :-)

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

In article m, Rob
reply@ng wrote:
On 22/06/2012 12:40, Jim Lesurf wrote: snip/

2) SACD is a proprietary format for 'filing' the data on a DVD,
devoted to audio in the 'DSD' 1-bit format. The point being to make
the data hard to rip, so far as I can tell. If it were a normal DVD it
would have a normal DVD filter root and could be seen on a computer.


Bit more to it than that? -

Yes, quite a lot. But the basic point was that Sony/Philips wanted an
'improved' *commercial* format they could still own the patent rights to
once Audio Cd patents lapsed. And to try and block the ability to 'rip' the
discs.

http://en.wikipedia.org/wiki/Super_Audio_CD

That strikes me as the right way of doing things, if the recording
process is handled correctly.

I can't say I agree. For two general reasons.

1) There are actually some fundamental problems with DSD. This has been
explored in a number of AES papers over the years. The conclusion is that
it may be OK as a consumer output format (for the above reasons) but it has
problems as an initial recording or archive format as it produces
degradations that LPCM avoids.

2) It uses DVD as the physical layer. You could easily get longer
recordings times on a DVD using LPCM loss-free formats like high resolution
flac. If based on 96k / 24bit, around four times as much. And rather more
than double for 192k /24 bit.

However the snag for companies is that flac on a 'normal' DVD would
facilitate the user being able to transfer the recordings to their computer
systems, etc, and play or digitially modify it (e.g. for room correction)
as *they* choose. Whereas SACD encrypts the DSD data stream.

You can certainly argue that SACD can be 'better' than Audio CD in
bandwidth/range product. This is simply a manifestation of Shannon's Law in
action. But other - rather more open - formats on DVD would be even better
since they avoid the inefficiency and problems of DSD.

Ask yourself why companies prefer to promote SACD when you can download
96k/24 and 192k/24 flac. The reason seems to me to be that some companies
really want to prevent you doing as you might prefer with the music you
have bought. It would be quite possible to have a data DVD level as a
hybrid with an audio CD, and give you the high rez. But it doesn't
happen...

Incidentally, if I had the time, I'd have a close look at the DBT and
other comparison tests mentioned on that wiki page. I find this
'measurement' of listening experiences highly suspect. Not sure why
though!

Not looked at that at present so can't comment.

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

"Jim Lesurf" wrote in message
...
In article , Dave C
wrote:

"Jim Lesurf" wrote in message
...
In article m, Rob
reply@ng wrote:
On 18/06/2012 11:05, Jim Lesurf wrote:

snip

In this case the general result on a *non* HDCD player is to squash
any peaks, distort sustained loud sounds, and lift the quieter parts
by about 6dB. i.e. pretty much like the kind of idiotic 'loudness'
treatments inflicted by those obsessed with 'louder is better'.


Snip

Hi Jim - very interesting reply to Rob. The bit that specifically stood
out is the bit I've left quoted above. My understanding - admitedly
based only on a handful of Telarc SACD's, is that there are two layers
on the CD. One for conventional players and one that only HDCD players
can find....

The blurb sheet of Telarc SACD 60516...has a diagram showing two layers
on the CD, one DSD which has both 2 channel and 5.1 and a conventional
CD layer conforming to the original CD standard for dynamic range etc.

are these Telarc discs not what you mean by HDCD?

Yes and no, m'lud. :-)

If they are like the few 'Linn Records' SACD/HDCD hybrids I have then the
'CD layer' is certainly playable on a normal audio CD player. One of the
points of HDCD is that it is *claimed* to be 'compatible' with audio CD
players and will thus play in them. But it may also be HDCD as outlined
below.

To some extent here, the problem is to clarify the wording and distingush
the 'container' from the 'contained'.

Right. These Telarc discs seem to be "correctly conceived" in the sense that
the normal CD layer is specifically redbook CD and they are at pains to
claim linear PCM with no compression etc etc.


I have a few HDCD discs that were sold to me as 'audio CDs' and have a
single layer. They play on normal audio CD players but are HDCD branded,

I've not come across any of these, a case of missing the point really I
would have thought. Although I suppose given the plethora of hideously
recorded discs these days perhaps the masses just don't care.

etc.

I also have a few hybrid discs. These have a 'DVD layer' and a 'CD layer'.
With the DVD (physical) layer containing SACD format DSD data and the CD
(physical) layer containing 'red book' audio CD. No HDCD involved. (e.g.
the new EMI 'Signature' series which I quite like.)

This is the only type I had come across. Now carefully avoiding the others



I also have a few hybrid discs with the 'DVD layer' containing SACD/DSD,
but the 'CD layer' containing HDCD format data samples in the 'red book'
format for an audio CD. (e.g. some Linn records discs.)


snip

Dave

In article , Dave C
wrote:

"Jim Lesurf" wrote in message
...



I have a few HDCD discs that were sold to me as 'audio CDs' and have a
single layer. They play on normal audio CD players but are HDCD
branded,

I've not come across any of these, a case of missing the point really I
would have thought.

My interest in HDCD as a topic was sparked as a result of my deciding to
buy some Joni Mitchell CDs. I have some of the old LPs and had recently
heard a program about her from a Jazz POV on R3. This made me get some
CDs to explore more of her output (and to compare in some cases with my
old, worn, LPs).

Some of the CDs seem to be plain ol' CDs. But other are 'remastered' ones
which have the HDCD logo. When sold they were only offerred as CDs with no
mention of HDCD. I suspect that is very common as most retailers won't
notice the HDCD logo or have any awareness of what it might mean.

It rapidly became clear that the 'HDCD' sounded quite loud and level
compressed. Although in other ways they sounded quite good (or at least two
did, and one didn't).

At first I thought this was the result of the 'Loudness War'. But then
started to wonder if it was caused by them being HDCD. The old issue CDs
were *not* so loud.

Although I suppose given the plethora of hideously recorded discs these
days perhaps the masses just don't care.

I do wonder if some in the music biz think HDCD is 'better' as a result of
a form of double-think. They take for granted that most buyers feel that
"louder is better", but that some audio fans will want wider dynamics more
faithful to the original.

If so, they may feel that the level compression HDCD can cause when the
result is played as a normal Audio CD will be *liked* by the 'mass
audience'. And that the fact that HDCD decoding will 'expand' this
compression to get back to more like the uncompressed source will be
preferred by audio enthusiasts.

On that basis I guess you can argue that HDCD caused compression is
'preferrable' to conventional level compression as those who wish can
correct it on replay by using a suitable player/decoder/software.

But if all that *is* so, it exposes one fact. That the music biz still
bases that on its faith-system that people *want* level-compressed music.
Even to have old recordings that were *not* so compressed when they became
famous on LP to now be compressed.

And another fact is that - for most rock/pop/jazz - there really is no need
to compress for CD. The music has a typical dynamic range that is well less
than that which plain LPCM CD can convey. So a plain non-HDCD could sound
as good as the correctly-decoded HDCD if both were made with the same care.
The only cost would be the listener having to adjust the volume control
slightly.

I can - potentially - see more point for the low-level gain variations that
HDCD can (or is said to) apply for something like classical orchestral
music. In such music you can often have sustained passages that are more
than 40dB below the peaks. So some slow and gradual level adjustments that
can be 'corrected' by those who choose may make sense. But almost no
rock/pop music is like this.

OTOH it may be that HDCD may simply have become essentially a 'brand name'
that some remasterers/labels can use for PR purposes. "Must be good. Its
HDCD". The same may well be true of some SACDs. Thus - as ever - we
probably have some people using HDCD for good reasons, and possibly
ontaining improved results, but others simply using it as a marketing
gimmic. (In some cases it may be the person doing the remastering using it
as their individual gimmic to make them more of a magician.)

For all I know, it may even be the case that HDCD sometimes acts as a
protection mechanism against some idiots doing remastering. If they have no
idea how it works it may sometimes help preserve info on the disc that they
would otherwise crush away in their obsession with loudness.

Whatever, I do doubt most people who use it have a clue what it does in any
detail. It is almost impossible to find out! :-)

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

On 18/06/2012 16:23, Jim Lesurf wrote:

AIUI MicroSoft took his code and say they put it into their software
players. But they bought the HDCD Patents. I have my doubts they actually
know or care about the details beyond it being another 'feature' they can
offer.

It's a while since I looked at it but I thought Windows Media Player
would decode HDCD if you have a 24-bit sound card.
WMP11 on my laptop shows 'HDCD' in the bottom left corner when playing
an HDCD.

And I thought there were programs available that could intercept data
going to a soundcard and copy it to a file,
though whether these work in 24-bit I don't know.

--
Eiron.