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CD audio is not good enough, CD Standard is bad quality
Joseph
post May 1 2003, 04:29
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Sound quality is a complex subject, and one that has been thrashed
out elsewhere time after time. Nonetheless I'll give it a bit of a
spin here, without getting all technical, in order to justify why I
think CD audio is not good enough.

When I complain about CD sound I am not doing so as some sort of
retrograde vinyl lover who can't change with the times. :-) I am
simply saying that the sound of the CD I am listening to has audible
problems and does not match what I expect the creators wanted. This
can be measured by how closely the CD replicates the master. Of
course in most cases I don't get to hear the master, so much is
guesswork. However, as a trained audio engineer I have *some* idea of
what is expected and can certainly compare CDs to the masters I
produce.

CDs improved on vinyl in many ways, notably in reduced noise floor,
phase artifacts, and crosstalk; ease of handling; and accurate
handling of low frequency stereo information. But CDs are inferior to
vinyl in frequency response and degradation characteristics. If a CD
gets a scratch you hear unlistenable white noise; if a record gets a
scratch you hear a DJ. ;-)

Going further, some may "prefer" the sound of vinyl precisely because
of the distortions it introduces. These include rounded signal peaks
and second-order harmonics, as well as the aforementioned phase
issues. All of these introduce a "warm" sound that is palatable to
many. Whether I like that sound or not, I prefer to hear what the
artist intended. If they wanted harmonics they could have used a
tube. And so on.

A bit more is in order about error correction. Most errors are
corrected by CD players, but this can produce tiny glitches of noise
that most people do not notice. I notice them. It's not that I have
better ears; once I point them out you can hear them as well. Of
course, the better the music reproduction system the more noticable
these are. (Though contrary to this, the better the CD player error
correction, the less you'll hear.) For most people with crappy
stereos it's not an issue.

I do not think that there is anything inherently wrong with digital
sound encoding, only that the 44.1KHz sampling rate and 16 bits per
sample are not good enough. Currently, studios use 96KHz and 24 (or
32) bits throughout the recording chain process, and must reduce this
down to consumer standards for replication. There's probably a good
reason why those people most highly trained in listening don't think
CD quality is good enough for recording. It's simply because their
ears tell them so.

You may be interested to know that the current CD standard was a
matter of much compromise between the American, European, and
Japanese manufacturers. I can remember reading some of the research
articles at the time (I was in university). The Japanese insisted
that 100KHz and 24-bit (if memory serves on the exact numbers) were
required for accurate reproduction. But the others argued that no-one
would hear the difference and it would reduce cost and time to market
if the lower standard was adopted. And so, unfortunately, it was.

Another big problem with many CDs is the terrible job of mastering.
Back in vinyl days you really had to know what you were doing to
adjust the master tape to the deficiencies of the medium. There were
relatively few mastering engineers, but they knew their job. Today
almost anyone thinks they can master, and so they do... badly.

So the problems with CD can be summarised as: insufficient frequency
response, insufficient resolution, poor mastering, nasty error
characteritics, and cases that break all the time. ;-)

MP3s inherit all of these except the bit about the cases.

-- robin
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2Bdecided
post May 2 2003, 10:34
Post #2


ReplayGain developer


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From: Yorkshire, UK
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QUOTE (Joseph @ May 2 2003 - 05:54 AM)
Nyquist called for a *minimum* of 2x the frequency. Many papers have
shown that the bare minimum is not sufficient. Some are even
available on the web, if you choose to go looking.

Can you provide some links please? I may have read them, but I always like something new. If you search on this forum, you'll find this is one of my favourite topics (I nearly did a PostDoc on it), and I'm not always in agreement with KikeG wink.gif

QUOTE
But never mind theory. In practice there are many people who can hear
the deficiencies caused by low sampling rates, usually in terms of
loss of clarity in the high end.


This is not my experience. The difference between 44.1k and 96k is like the difference between a good and bad amplifier (for example) - the music just sounds more "real", and the sound stage is slightly better defined. It's got nothing to do with frequency response, or weakness/improvement in any particular range. If anything, I thought the bass was effected most, but that's a quirk of human percetion, rather than there actually being any difference in the reproduction of the bass.

What I'm saying is that what you report is the "expected" improvement. Whenever people do something, and then magically hear the improvement that they expected, there's one word springs to mind...


QUOTE
...it's nice to remove one source of loss or
distortion from the signal chain, because certainly signals have been
recorded and manipulated that exceed 16-bit. I'd rather overkill than
underkill (if there is such a word).


Of course there's no harm. It's questionable if there's any good, but I agree that theoretically there could be. Again, what experience people actually hear does not match the expectation: the improvement due to increased bitdepth has nothing to do with decreasing the background nosie from 7dB SPL -10dB SPL (typcal measurements if you use an SMPTE calibrated system to replay 16 and 20 bit audio). At least not audibly. It sounds like something completely different - it removes some hash and distortion. Distortion which, theoretically, doesn't exist.


QUOTE
> The system is very
> robust, and if you commonly encounter audible errors than I suggest
you
> replace damaged CDs or invest in a good quality CD player.

You talk of using a low-end "Techniques" and then say *I* need a
better player. Ha!

> In practice my experience is
> that error correction is not an issue for CD, so I find your claims
to be
> unusual and suspect.

It depends on the CD medium. Metal-stamped CDs are less of a problem
than dye-based CD-Rs. I have examples of these that regularly
demonstrate painful noise that even the most casual listeners can
hear.


If you're expecting to play CD-Rs on your player, but it gives audible noise on them, then something's wrong. Are the CD-Rs burnt with good data? Are their errors in the original .wavs? If not, then it's a compatability problem between the CD-R and your player. It happens. It doesn't mean that this is a general situation with most players and discs.

As for damaged discs: Anyone who wants to play a disc with a 1mm scratch on it, LP or CD, probably isn't too concerned with the sound quality. If they are, they should take better care of their software, or replace it often!

QUOTE
That is the problem. You want to *see* the evidence. Open your ears
and you can *hear* it plain enough.


Not everyone has the equipment, inclination, or ears to do this. FWIW I heard the difference between 44.1 and 96k using some excellent DCS DACs and excellent amps and speakers. I learnt to hear the difference in a sighted demonstration, and then picked out 44.1k when they were switched without me knowing which was which.

At the other end of the scale, I can pick out 32kHz on my cheapest soundcard at home (and, for my hearing, 32kHz should be enough). The reason is obvious: the soundcard is terrible!

However, at home with my audiophile 2496, I can't hear any advantage of 24 bits over 16, or 96k over 44.1. That's just the way it is!



QUOTE
I don't see how it can possibly hinder your
enjoyment of music if others choose to listen to a different digital
standard.


Well, if almost everyone in the world listened to 128kbps mp3, that's what the record companies would sell, and everyone here would be very unhappy! As it is, most people prefer overcompressed rubbish, and we are mostly unhappy with this.

DVD-A (and probably SACD) can't sound worse than CD (though some early DVD-A players were reportedly questionable), but you've got to be very sure that they're better before you're going to think about spending huge amounts of money on them. Blind tests to prove this point are notable by their absence - could it be that the "advantages" just aren't that big?

Cheers,
David.

P.S. - Don't point me to audiophile forums where people are saying how great there new expensive SACD player sounds. They might be right, but they're hardly unbiassed. I never believe anyone who tells me how great their new toy is anymore. For example, there are far too many people in the UK saying how great the picture on their new digital 16:9 TV is. The truth is usually an analogue 4:3 image stretched to 16:9 (wow - yeah - that's great - the people all look so, er, fat!); or a digital image with so much blockiness that the folks at doom9.org would tell you to re-encode it! The "new toy" syndrome is very strong. People don't want to think that they've wasted their money, or that they've been conned.
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Posts in this topic
- Joseph   CD audio is not good enough   May 1 2003, 04:29
- - bryant   You're absolutely right!! Those CD cas...   May 1 2003, 04:48
- - boojum   Joseph, in general I agree with your post. But th...   May 1 2003, 04:57
- - mrosscook   Joseph, Your post argues that a lot of current CD...   May 1 2003, 05:16
- - paranoos   I have to agree completely with your statement abo...   May 1 2003, 05:18
- - floyd   QUOTE (Joseph @ Apr 30 2003 - 09:29 PM)Curren...   May 1 2003, 05:43
- - Delirium   I'm pretty sure you're, frankly, incorrect...   May 1 2003, 06:14
- - sjk   QUOTE (paranoos @ Apr 30 2003 - 08:18 PM)I ha...   May 1 2003, 06:34
- - AstralStorm   QUOTE (Delirium @ May 1 2003 - 07:14 AM)To co...   May 1 2003, 07:32
- - 2Bdecided   Whilst I'm a fan of higher sample rates (in th...   May 1 2003, 10:51
- - dev0   I agree with Paranoos here completely. If masterin...   May 1 2003, 11:01
- - Uosdwis R. Dewoh   The CD standard is often taking an unfair amount o...   May 1 2003, 12:44
- - DonP   I believe the 16/44 rates are the numbers that fel...   May 1 2003, 14:32
- - Joseph   paranoos wrote: > I have to agree completely w...   May 1 2003, 16:32
- - DigitalMan   QUOTE (Joseph @ May 1 2003 - 07:32 AM)paranoo...   May 1 2003, 18:06
- - KikeG   Well, all there issues have been discussed here fr...   May 1 2003, 20:28
- - Pio2001   Joseph wrote : QUOTE CDs are inferior to vinyl in...   May 1 2003, 21:22
- - buzzy   One of the great things about HA is that discussio...   May 1 2003, 22:33
- - Uosdwis R. Dewoh   QUOTE (Joseph @ May 1 2003 - 04:32 PM)> Al...   May 1 2003, 22:41
- - KikeG   QUOTE (Pio2001 @ May 1 2003 - 09:22 PM)What...   May 2 2003, 00:21
- - Pio2001   About audible clicks, I must say that many recordi...   May 2 2003, 01:12
- - DonP   QUOTE (Pio2001 @ May 1 2003 - 03:22 PM)Actual...   May 2 2003, 01:17
- - Joseph   DigitalMan wrote > 1) Nyquist does not require...   May 2 2003, 06:54
- - Miles   QUOTE (Joseph @ May 1 2003 - 05:29 AM)... you...   May 2 2003, 08:21
- - 2Bdecided   QUOTE (Pio2001 @ May 1 2003 - 08:22 PM)2bdeci...   May 2 2003, 10:02
- - 2Bdecided   QUOTE (Joseph @ May 2 2003 - 05:54 AM)Nyquist...   May 2 2003, 10:34
- - Pio2001   QUOTE (Joseph @ May 2 2003 - 08:54 AM)It depe...   May 2 2003, 11:41
- - mrosscook   Joseph, you end your last post by saying, QUOTE B...   May 2 2003, 16:18
- - DonP   QUOTE (Pio2001 @ May 2 2003 - 05:41 AM)That...   May 2 2003, 16:43
- - bryant   QUOTE (mrosscook @ May 2 2003 - 07:18 AM)Base...   May 2 2003, 18:34
- - DigitalMan   QUOTE (Joseph @ May 1 2003 - 09:54 PM)Joseph ...   May 2 2003, 18:35
- - KikeG   QUOTE (Joseph @ May 2 2003 - 06:54 AM)Nyquist...   May 2 2003, 18:58


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