[Ardour-Users] Ardour-Users Digest, Vol 76, Issue 5

Tue May 18 19:22:34 PDT 2010

On Tue, May 18, 2010 at 8:45 PM, Ross Johnson
<Ross.Johnson at homemail.com.au>wrote:

>
> But these are both different purposes to finding zero-crossings, which is
> to find points where the track may be cut without introducing transients - a
> pretty common requirement but possibly not trivial to do properly.
>
>
actually, its not possible to do it properly unless you do destructive
editing. to get true "click" free edits means that there can be no
discontinuity between adjacent samples. in the context of the question,
there are only two ways to do this:

    1) find places where the sample value is itself zero
OR
    2) find places where two adjacent sample values are positive and
negative and change one of them to zero, and do the edit immediately before
or after that

given that the incidence of samples that are precisely valued at zero, its
pretty clear that (1) is not a realistic option. and if you don't want to
make changes to the audio data (something ardour works very hard to avoid
every doing), (2) is also not an option.

now, clearly, if you knew the material that was going to be placed on either
side of a "junction" before doing the cuts, you could look for places where
the sample values of the left-hand side piece and right-hand side piece are
compatible. unfortunately knowing this ahead of time is pretty limiting to
editing workflow.

fundamentally, any time you "cut" audio, you will induce transients unless
the signal has some rather unusual properties. whether these transients
matter depends on the material and the context. in general, its much better
to apply a short fade (which generates some harmonic noise of its own) than
try to do a cut in "the right place".

--p

>
>  Best,
>> P
>>
>>
>>
>>
>> On 18 May 2010, at 21:01, ardour-users-request at lists.ardour.org wrote:
>>
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>>> Today's Topics:
>>>
>>>  1. zero crossings when editing audio (Paul Schwebel)
>>>  2. Re: zero crossings when editing audio (J?rn Nettingsmeier)
>>>  3. Re: zero crossings when editing audio (Ray Rashif)
>>>
>>>
>>> ----------------------------------------------------------------------
>>>
>>> Message: 1
>>> Date: Mon, 17 May 2010 22:33:03 -0700 (PDT)
>>> From: Paul Schwebel <pschwebe at yahoo.com>
>>> To: ardour-users at lists.ardour.org
>>> Subject: [Ardour-Users] zero crossings when editing audio
>>> Message-ID: <787382.6972.qm at web111504.mail.gq1.yahoo.com>
>>> Content-Type: text/plain; charset=us-ascii
>>>
>>> When editing audio, is there a way to easily set the edit area to a zero
>>> crossing? I can't find any such option and the tutorial doesn't really cover
>>> edits of this kind.
>>>
>>> Thank you,
>>> -Paul
>>>
>>>
>>> ------------------------------
>>>
>>> Message: 2
>>> Date: Tue, 18 May 2010 08:59:46 +0200
>>> From: J?rn Nettingsmeier  <nettings at stackingdwarves.net>
>>> To: ardour-users at lists.ardour.org
>>> Subject: Re: [Ardour-Users] zero crossings when editing audio
>>> Message-ID: <4BF23AE2.6080808 at stackingdwarves.net>
>>> Content-Type: text/plain; charset=ISO-8859-1
>>>
>>> On 05/18/2010 07:33 AM, Paul Schwebel wrote:
>>>
>>>> When editing audio, is there a way to easily set the edit area to a zero
>>>> crossing? I can't find any such option and the tutorial doesn't really cover
>>>> edits of this kind.
>>>>
>>>
>>> afaik, there isn't. but it doesn't help much, anyways. the problem is
>>> that there will be clicks whenever the waveform has a "sharp corner",
>>> and this can happen even when both spliced ends are at a zero crossing.
>>> ardour will use very short fades to get rid of clicks, which works
>>> better.
>>>
>>> hth,
>>>
>>> j?rn
>>>
>>>
>>> --
>>> J?rn Nettingsmeier
>>> Lortzingstr. 11, 45128 Essen, Tel. +49 177 7937487
>>>
>>> Meister f?r Veranstaltungstechnik (B?hne/Studio), Elektrofachkraft
>>> Audio and event engineer - Ambisonic surround recordings
>>>
>>> http://stackingdwarves.net
>>>
>>>
>>>
>>> ------------------------------
>>>
>>> Message: 3
>>> Date: Tue, 18 May 2010 16:00:19 +0800
>>> From: Ray Rashif <schivmeister at gmail.com>
>>> To: ardour-users <ardour-users at lists.ardour.org>
>>> Subject: Re: [Ardour-Users] zero crossings when editing audio
>>> Message-ID:
>>>    <AANLkTikZkrzmgM9uzBnu8v48X7HwZMrZRyRJV9q-NeAI at mail.gmail.com>
>>> Content-Type: text/plain; charset=ISO-8859-1
>>>
>>> On 18/05/2010, J?rn Nettingsmeier <nettings at stackingdwarves.net> wrote:
>>>
>>>> On 05/18/2010 07:33 AM, Paul Schwebel wrote:
>>>>
>>>>> When editing audio, is there a way to easily set the edit area to a
>>>>> zero
>>>>> crossing? I can't find any such option and the tutorial doesn't really
>>>>> cover edits of this kind.
>>>>>
>>>>
>>>> afaik, there isn't. but it doesn't help much, anyways. the problem is
>>>> that there will be clicks whenever the waveform has a "sharp corner",
>>>> and this can happen even when both spliced ends are at a zero crossing.
>>>> ardour will use very short fades to get rid of clicks, which works
>>>> better.
>>>>
>>>
>>> Is there even such a thing as set-edit-on-zero-crossing? I've always
>>> done seek-fix-and-match for regions that do not have a continuous
>>> waveform, i.e clicks. But often times you need sample-level zoom
>>> factor to fix the tricky ones.
>>>
>>>
>>> --
>>> GPG/PGP ID: B42DDCAD
>>>
>>>
>>> ------------------------------
>>>
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>>>
>>> End of Ardour-Users Digest, Vol 76, Issue 5
>>> *******************************************
>>>
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