On Sun, 07 Sep 2014 16:40:06 +0100, Jim Lesurf
wrote:

I can illustrate the real challenge here with an example.

http://jcgl.orpheusweb.co.uk/temp/ZoomCircled.png

This shows the start of side 2 of an LP of Brahms 1st Piano Concerto
(Barbirolli, Barenboim on EMI 1967) Its a lovely LP but has various various
'ticks' that are clearly audible in the quiet passages.

The tick shown here at about 6.42 sec from the start is audible with the
piano. Note the low modulation levels. The music is below about -25dB as
recorded (0dBFS was about +17dBRIAA) and the tick is smaller in amplitude
than the music.

This one is relatively easy to find by ear-eye *but* you have to zoom the
time and amplitude scales to be able to see it. If you don't the ripple at
the bottom of the previous cycle looks like the cause because it sticks out
of the displayed waveform, but it isn't.

Other ticks are harder to find. But even this one seems a challenge to find
by an 'automated' locator.

Doing an automatic locator for loud bangs is easy. But then so is seeing
them with Audacity! Question is if this kind of example can be detected by
something of the kind I've mentioned. Ideally a program that generates a
list of 'click candidates' that would find this but not be swamped with
false positives. I suspect its almost impossible, but wonder what people
think.

IIRC (its been quite a while since I last did such processing), the
declick function in CoolEdit Pro lists the number of clicks and pops
it finds in a selection before allowing you to apply the removal
process itself.

If the click/pop count looks suspiciously on the high side you can
try the effect and audition it afterward (I've assumed you would have
already auditioned it beforehand). If there's no obvious improvement,
or worse still, a degradation, you can simply undo the action.

I do recall, however, that I tended to avoid auto repair and manually
deal with the quieter sections where such noise would be a real
intrusion (after dealing with the grosser, obvious by eye, clicks and
pops). Here, when the small selected portion was largely the same low
level amplitude, I found I could get away with using auto-declicking
in most cases. Any recalcitrant clicks that escaped their well
deserved fate I would home in on and manually edit the sound samples,
if need be.

Any other larger clicks hiding amongst the louder passages were
usually undetectable by ear. In any case, I figured this would be a
problem best left to my grandchildrens' progeny to solve. :-)

There's only so much you can do before the benefit to effort ratio
falls to a vanishingly small value where you begin to question your
very existence. Hell! If I was content to listen to this stuff (warts
and all) before, the result I've got so far aught to be more than
enough to improve my listening pleasure. Enough already! Just give it
a rest and be happy! \-)

If you mess around enough with such processing, you'll find out what
that last paragraph is all about soon enough.



Took me hours to do side 1! 8-] Its only something I'd do for 'special
cases' where I really want to clean up as much as possible particularly
enjoyable examples. ... and this is a 2 LP set. 8-]


I think you're already getting a notion of what I was going on about
two paragraphs back. I think we all start off with an idealistic zeal
for 'perfection' (at least that was true enough in my case) before the
realism kicks in when the enormity of the task finally sinks in.

Just deal with the most obvious defects and leave the rest for future
generations to deal with when they might have access to better tools
by which to complete the task. After all, you've already completed the
most important task of digitising it in the first place even if you
never process it any further than topping and tailing the tracks.
--
J B Good