<<but maybe there would be some resistance to the delay if removal was called straight after recording.>>
There certainly would be a lot of resistance for an auto invocation of DC-offset removal immediately after recording.  Many of us have recording chains which are DC-offset free, or carry such miniscule DC that it's not really worth bothering about.  The only way I could countenance having such an auto invocation is if we also introduced a Preference setting to enable/disable it.

<<Another issue is that some people use "Amplify" to do the volume adjustment so never even find "Normalize". >>
We try to mitigate this through the documentation - the sample work-flows in the manual for  LP transcription and 78s transcription for example.  We should probably also include DC-offset removal recommendations in the "Your first recording" and the "Basic recording, Editing and Exporting" tutorials.  And yes, I realize that assumes users RTFM ...

Also if we do implement the proposal to create a new separate effect for DC-offset removal than this should draw people's attention to it more.  This is one of the prime reasons for the DC offset proposal for a new effect:  to stop it being "hidden" in the Normalize (see footnote).

<<Also removal needs to be done on import doesn't it (or on processing of the first edit thereafter)?>>
As above I would not want this auto-invoked unless there was a preference to enable/disable it.  It takes long enough to import stuff anyway. 

Peter

Footnote:  I note from reading Carla Schroder's recently released "The Book Of Audacity" that she doesn't mention DC offset removal until late in the editing process as part of Normalization.  I suspect that this is mainly because the DC removal is "buried" in Audacity's Normalize function - leading folk (including Carla) to believe that DC removal is a late-stage process that should be done with normalization, whereas we know that it is much better to remove it at a very early stage in the editing process.  I have pointed this out to her and I believe she will change her recommendations in the next edition of her book.
 




From: Gale Andrews <gale@audacityteam.org>
To: audacity-quality <audacity-quality@lists.sourceforge.net>
Sent: Wed, June 15, 2011 8:50:29 PM
Subject: Re: [Audacity-quality] Proposal to rationalize and improve Normalize, Amplify & DC


| From Martyn Shaw <martynshaw99@gmail.com>
| Tue, 14 Jun 2011 23:19:33 +0100
| Subject: [Audacity-quality] Proposal to rationalize and improve Normalize, Amplify & DC
> On 14/06/2011 17:57, Gale Andrews wrote:
> >
> > | From Martyn Shaw<martynshaw99@gmail.com>
> > | Tue, 14 Jun 2011 00:17:46 +0100
> > | Subject: [Audacity-quality] Proposal to rationalize and improve Normalize, Amplify&  DC
> >> On 13/06/2011 16:09, Peter Sampson wrote:
> >>> But I also note that Normalize with DC removal seems to take the same
> >>> time as DC removal on is own, which is not what I would expect.
> >>
> >> Both need the pass over the audio to measure the dc offset.  The
> >> second pass applies the dc removal and gain at the same time.  So both
> >> these cases take 2 passes (not a separate one for dc removal and
> >> amplify).  Does that make sense?
> >
> > Largely so. But the second pass has "more to do" if applying gain as
> > well as offset removal.  If this doesn't add anything much to the time
> > taken then it suggests the best way to apply DC offset may yet be to
> > bundle it with other processes rather than have it as its own menu
> > item.
>
> Removing dc offset is a fundamental thing that should be done to audio
> data when it is captured.  Bundling offset removal with another effect
> would just mean that people should run that one once they have
> captured their data.  What effect would that be?  Adjusting the
> amplitude to a known level?  Good idea!  Let's call it 'Normalize'!

Well there are lots of ideas on the Wiki:
http://wiki.audacityteam.org/wiki/Proposal_DC_Offset_removal

but maybe there would be some resistance to the delay if removal
was called straight after recording. Another issue is that some
people use "Amplify" to do the volume adjustment so never even
find "Normalize".

Also removal needs to be done on import doesn't it (or on processing
of the first edit thereafter)?



Gale


> >>> ----------------------------------------------------------------------
> >>> *From:* Martyn Shaw<martynshaw99@gmail.com>
> >>> *To:* "for identification, characterization, and prioritization of
> >>> bugs."<audacity-quality@lists.sourceforge.net>
> >>> *Sent:* Mon, June 13, 2011 12:40:25 AM
> >>> *Subject:* Re: [Audacity-quality] Proposal to rationalize and improve
> >>> Normalize, Amplify&  DC
> >>>
> >>> Hi Peter
> >>>
> >>> Most of what you are measuring there are probably disk accesses, but
> >>> that is important. My claimed increase in performance did not involve
> >>> listening to my disk drive (and was only a minor claim).
> >>>
> >>> I have just committed something that should improve results iff you
> >>> are not doing dc removal (I removed a pass over the data in that case).
> >>>
> >>> If I am testing timings of functions A, B and C, I would test A then B
> >>> then C then A then B etc, and take at least 3 goes at each, to average
> >>> out changes in my PC (antivirus etc.). Are you doing that?
> >>>
> >>> On the Progress box, we normally do 2 passes over the audio for each
> >>> track, one for analysis and one for processing. The one for analysis
> >>> of amplitude is no longer required (in my changes) but the one for dc
> >>> offset still is. So removal of dc should take longer and just
> >>> normalising shouldn't be much different from Amplify. Is that what
> >>> you see once you get my recent changes?
> >>>
> >>> Thanks for your input here!
> >>>
> >>> TTFN
> >>> Martyn
> >>>
> >>>
> >>>
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