autopilot;268175 Wrote: 
> But will an error that small even be perceivable to the human, or are we
> splitting hairs here?
Often, when EAC reports an error, the result is a "pop" on one of the
channels.  Zooming in on the error with the audio editor (I use Cool
Edit) usually reveals a single errant sample way out of line with the
rest of the curve.  The simple way to fix it is just to delete that
sample.  I've never been able to hear the result of a single deleted
sample.  Also, depending on how far out of line the errant sample is,
you may never hear it in the first place.

The latest batch of discs I'm reading has a Steppenwolf Greatest Hits
disc with 3 of 16 tracks with errors caused by pinholes in the aluminum
plating on the CD.  I've tried reading the tracks on 3 different drives
and am manually editing out the ticks where EAC didn't get a good
read.

With most discs, I get "All tracks accurately ripped", which I think is
pretty amazing!  Sometimes I get "Not in database" and every once in a
while I get "No tracks can be verified accurate; you may have a
different pressing".

One interesting thing I've noticed is on discs with mono tracks.  In
theory these discs could be self-checking since both channels should be
identical.  In practice, this is rarely the case; there is often a
slight channel imbalance coupled with high-frequency phase errors,
presumably caused because they were digitized by a stereo ADC.  However
a few times I have seen discs with (except for dither) numerically
identical channels.  And I've seen discs which AccurateRip verifies as
correct which have ocasional big blips when the channels are
differenced, indicating that the errors were written onto the disc by
the pressing plant.  Usually such errors are inaudible, which gives me
the idea that absolute numeric perfection is not really necessary nor
even always achieved with digital audio.

Some of the worst examples of very popular mono discs where the
channels don't even come close to matching are the early Beatles discs.
On certain tracks, the mono tape was played back on a stereo machine
with a stereo chain all the way to the ADC.  When the difference of the
channels is taken, every flaw in the master tape, folds, slices,
fingerprints, shedding oxide, etc is magnified.  The result is rather
bad!  EMI doesn't rate a very high score in my book for that one...


-- 
Timothy Stockman
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