In article , Don Pearce
wrote:
[snip]

I just don't understand why these sorts of CDs need to be mastered into
clipping. I can understand a CD being normalised to 0dBFS, but that
would mean one hit at 0dBFS once per CD, or at worse once per track, if
tracks are mastered individually. There's just no excuse for it.

ahem Anyone in the UK who is interested in this may find the December
issue of 'Hi Fi News' worth a read. Should be out in a couple of weeks.
:-)

Note also that even just one sample of a sequence at or near the 0dBFS
level may mean a reconstructed waveform with an excusion *above* this.


However, try as I might, I can't hear the clipping in the Diana Krall
and Norah Jones, even sighted, knowing when it takes place. The Amy
Winehouse is , however, very obvious.

As an experiment, I made up a 'test CD' a while ago to try on some friends
and colleagues. This consists of a set of tracks of various types of music
where the original peaks well below 0dB, and versions I deliberately
clipped. Apart from the clipped sections the two versions of each example
are sample-by-sample the same.

It has been interesting to see how hard/easy people have found identifying
the clipped version to be. :-)

This seems to agree with something I discovered 20+ years ago. When I
designed the Armstrong 730/732 amps I fitted a clipping indicator. It
turned out to be quite difficult to hear the clipping in many cases -
although admitted this is at levels well over 200Wpc so I am not sure what
the speakers (or ears!) were doing in some cases at these levels in a
normal UK domestic situation. 8-]

Do remember that lighting the top bit light does not necessarily imply
clipping - it is just another value, and if the signal isn't trying to
go beyond that, it hasn't clipped.

Pop recordings use heavy compression, and when this is done in the
digital domain it is quite possible to have sufficient control to peak
to the same value every time. There is no reason not to normalize the
result up to max level.

Alas, my recent experience confirms that a number of CDs have successions
of samples well within 0.05dB or so of the peak values allowed on CD-A.
Level compression seems much more common, but flat-top clipping seems far
from rare. As you say, this seems utterly insane when many rock/pop CDs
squash the sound into a range of about 10dB - on a medium that should be
able to offer a range over a million times greater!

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

"Jim Lesurf" wrote in message


As an experiment, I made up a 'test CD' a while ago to
try on some friends and colleagues. This consists of a
set of tracks of various types of music where the
original peaks well below 0dB, and versions I
deliberately clipped. Apart from the clipped sections the
two versions of each example are sample-by-sample the
same.

It has been interesting to see how hard/easy people have
found identifying the clipped version to be. :-)

Depending on the music, it can be hard or easy.

This seems to agree with something I discovered 20+ years
ago. When I designed the Armstrong 730/732 amps I fitted
a clipping indicator. It turned out to be quite difficult
to hear the clipping in many cases - although admitted
this is at levels well over 200Wpc so I am not sure what
the speakers (or ears!) were doing in some cases at these
levels in a normal UK domestic situation. 8-]

Case in point is the clipping indicator on QSC power amps. It starts
visibly illuminating at clipping that amounts to something like 0.02% THD.
Again depending it can be found to be flashing quite a bit, and yet the
sound may not be all that bad-sounding.

Do remember that lighting the top bit light does not
necessarily imply clipping - it is just another value,
and if the signal isn't trying to go beyond that, it
hasn't clipped.

Pop recordings use heavy compression, and when this is
done in the digital domain it is quite possible to have
sufficient control to peak to the same value every time.
There is no reason not to normalize the result up to max
level.

Many converters, espcially the cheap ones, won't convert cleanly right up to
FS. Keeping peaks 0.5-1 dB below FS will help ensure clean performance with
cheaper equipment.

Alas, my recent experience confirms that a number of CDs
have successions of samples well within 0.05dB or so of
the peak values allowed on CD-A. Level compression seems
much more common, but flat-top clipping seems far from
rare.

Agreed.

As you say, this seems utterly insane when many
rock/pop CDs squash the sound into a range of about 10dB
- on a medium that should be able to offer a range over a
million times greater!

There are two sorts of logical reasons to clip music. One is that it
constitutes an EFX. It's pretty well known that distorted music often sounds
louder than music that is cleanly reproduced. The other is the fact that
music with limited dynamic range can be more suitable when listening to
music is not the most important thing that the listener is doing.

In rec.audio.tech Jim Lesurf wrote:
In article , Don Pearce
wrote:
[snip]

I just don't understand why these sorts of CDs need to be mastered into
clipping. I can understand a CD being normalised to 0dBFS, but that
would mean one hit at 0dBFS once per CD, or at worse once per track, if
tracks are mastered individually. There's just no excuse for it.

ahem Anyone in the UK who is interested in this may find the December
issue of 'Hi Fi News' worth a read. Should be out in a couple of weeks.
:-)

Note also that even just one sample of a sequence at or near the 0dBFS
level may mean a reconstructed waveform with an excusion *above* this.


True dat. This article may be old news to some readers here, but it
explains intersample overs (0dB+ levels)

http://www.tcelectronic.com/media/ni...0_0dbfs_le.pdf


Alas, my recent experience confirms that a number of CDs have successions
of samples well within 0.05dB or so of the peak values allowed on CD-A.
Level compression seems much more common, but flat-top clipping seems far
from rare. As you say, this seems utterly insane when many rock/pop CDs
squash the sound into a range of about 10dB - on a medium that should be
able to offer a range over a million times greater!


It's even more discouraging to find it on supposedly 'hi rez' media like
DVD-A

This page shows various digital remasters of 'Roundabout' by Yes over the
years. The DVD-A version doesn't clip, and doesn't have 'flat top' peaks,
but it *has* been compressed to all heck all the same.

http://www.m-ideas.com/sullivan/audition/roundabout.htm

(The last one is just crazy -- and that's from the currently-available
"Fragile" CD from Rhino.)


___
-S
"As human beings, we understand the world through simile, analogy,
metaphor, narrative and, sometimes, claymation." - B. Mason