From: Alexander Schreiber (als_at_thangorodrim.de)
Date: Tue Feb 17 2004 - 10:47:35 PST
On Tue, Feb 17, 2004 at 07:10:30PM +0100, Robert Benschop wrote:
> On 17-feb-04, at 18:14, David M. Ensteness wrote:
> > I also am unclear how laser size would impact it since the same
> > amount of data is present on the copy as the original.
>
> Picture the data written in a choppy way, ever seen a CD player insides
> when it turns?
> Probably one of worst designs in mechanical engineering, still beats
> how they got it to sway so much.
It's consumer equipment were every cent saved counts and you still
expect quality?
> Some high-end CD players will tell you when they do fault corrections,
Which would be practically always. Keep in mind, that on an audio CD,
there is already a lot of raw capacity used for error correction codes.
And that is only to keep the final error rate acceptably low for audio.
Fortunately, since we are dealing with audio data, any remaining spikes
can be hammered flat enough with low pass filters.
There are, btw, several steps to handling data errors in audio:
- fix with the error correction codes (happens practically all the
time and only the circuits doing it notice),
- interpolate samples (several methods),
- mute this sector (== 1/75 s silence),
I guess that only the last one would be noticable and its probably this
step that causes the "damn, too many errors"-light on your player to
light up.
Data CDs have a second error correction layer _on_ _top_ of that - thats
what most of the difference between 2352 byte audio and 2048 byte data
sector size is used for.
> if they're sensitive enough they'll come on more often with certain
> copied discs.
> Try and burn a CD on top speed and one on 1x and see if you can hear
> the difference.
That is more a function of:
- the quality of your CD-burner (bad CD burners have seriously
exploding write error rates upon getting close to maximum speed),
- the overall digital recording quality of your CD burning setup
(writing with 40x speed _requires_ a guaranteed constant dataflow
of 6000 kilobytes/second - if this drops too much (not all that much,
since CD burners tend to be low on buffer memory), you'll get drop
outs in the recording),
Of course, using low quality CD-Rs isn't going to help here. The
chemistry of the organic dye in the CD-Rs is _not_ something you can
brew up in your garden shack and expect to get stable results ;-)
Regards,
Alex.
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