Re: [LAD] Mixing audio: Noiseless volume changes

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To: Tim E. Real <termtech@...>
Cc: <linux-audio-dev@...>
Date: Monday, March 18, 2013 - 10:47 pm

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On Mon, Mar 18, 2013 at 5:50 PM, Tim E. Real wrote:

> Hi again. Looking for any advice, tips, tricks, anecdotes etc.

You cannot avoid artifacts in the audio. The only question is what is the
nature of the artifacts.

> If I use a zero-crossing/zero-value detector and apply volume changes

Zero crossing stuff is a completely bogus idea that needs to be eliminated
from the lexicon of audio software. You will not be accomplishing anything
trying to use such a technique, other than introduce even more artifacts
(and rather horrendous ones at that). Even zero-valued samples are not
particularly useful - keep in mind that what defines transducer (read:
speaker) behaviour is power, not instantaneous volume.

Just use sensibly short ramped changes. For the record, Ardour uses 64 or a
JACK period size, whichever is, hmm, larger or smaller, can't recall.

--p

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On Mon, Mar 18, 2013 at 5:50 PM, Tim E. =
Real <termtech@rogers.com> wrote:
Hi again. Looking for any advice, tips, tricks, anecdotes etc.

I want to eliminate or reduce 'zipper' noise on volume changes.
So I'm looking at two techniques:
Zero-crossing / zero-value signal detection, and slew-rate limiting.
Code is almost done, almost ready to start testing each technique.
Each technique has some advantages and disadvantages.

If I use a slew-rate limiter, I figure for a sudden volume factor change
=A0from 0.0 to 1.0, if I limit the slew rate to say 0.01 per sample then af=
ter
=A0100 samples the ramp will be done.
But even with a fine ramp, this still might introduce artifacts in the audi=
o.You cannot avoid artifacts in the audio. The on=
ly question is what is the nature of the artifacts. =A0=A0

If I use a zero-crossing/zero-value detector and apply volume changesZero crossing stuff is a completely bogus idea that nee=
ds to be eliminated from the lexicon of audio software. You will not be acc=
omplishing anything trying to use such a technique, other than introduce ev=
en more artifacts (and rather horrendous ones at that). Even zero-valued sa=
mples are not particularly useful - keep in mind that what defines transduc=
er (read: speaker) behaviour is power, not instantaneous volume.=A0
Just use sensibly short ramped changes. For the record, Ardour uses 64 =
or a JACK period size, whichever is, hmm, larger or smaller, can't reca=
ll.--p

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Messages in current thread:
[LAD] Mixing audio: Noiseless volume changes, Tim E. Real, (Mon Mar 18, 9:50 pm)
Re: [LAD] Mixing audio: Noiseless volume changes, Fons Adriaensen, (Mon Mar 18, 11:05 pm)
Re: [LAD] Mixing audio: Noiseless volume changes, Paul Davis, (Mon Mar 18, 10:47 pm)
Re: [LAD] Mixing audio: Noiseless volume changes, Tim E. Real, (Mon Mar 18, 11:05 pm)
Re: [LAD] Mixing audio: Noiseless volume changes, Tim E. Real, (Mon Mar 18, 11:43 pm)
Re: [LAD] Mixing audio: Noiseless volume changes, Fons Adriaensen, (Mon Mar 18, 11:58 pm)
Re: [LAD] Mixing audio: Noiseless volume changes, Tim E. Real, (Tue Mar 19, 12:31 am)
Re: [LAD] Mixing audio: Noiseless volume changes, James Morris, (Mon Mar 18, 11:28 pm)
Re: [LAD] Mixing audio: Noiseless volume changes, Fons Adriaensen, (Mon Mar 18, 11:45 pm)
Re: [LAD] Mixing audio: Noiseless volume changes, Harry van Haaren, (Tue Mar 19, 2:09 am)
Re: [LAD] Mixing audio: Noiseless volume changes, Tim Goetze, (Tue Mar 19, 3:17 am)
Re: [LAD] Mixing audio: Noiseless volume changes, Fons Adriaensen, (Tue Mar 19, 1:02 pm)
Re: [LAD] Mixing audio: Noiseless volume changes, Tim Goetze, (Tue Mar 19, 1:53 pm)
Re: [LAD] Mixing audio: Noiseless volume changes, Fons Adriaensen, (Tue Mar 19, 3:08 pm)
Re: [LAD] Mixing audio: Noiseless volume changes, Tim Goetze, (Tue Mar 19, 3:37 pm)
Re: [LAD] Mixing audio: Noiseless volume changes, Fons Adriaensen, (Tue Mar 19, 4:31 pm)
Re: [LAD] Mixing audio: Noiseless volume changes, Tim Goetze, (Tue Mar 19, 7:06 pm)
Re: [LAD] Mixing audio: Noiseless volume changes, Charles Z Henry, (Tue Mar 19, 10:26 pm)
Re: [LAD] Mixing audio: Noiseless volume changes, Fons Adriaensen, (Tue Mar 19, 10:57 pm)
Re: [LAD] Mixing audio: Noiseless volume changes, Charles Z Henry, (Tue Mar 19, 11:12 pm)
Re: [LAD] Mixing audio: Noiseless volume changes, Fons Adriaensen, (Tue Mar 19, 11:30 pm)
Re: [LAD] Mixing audio: Noiseless volume changes, Fons Adriaensen, (Tue Mar 19, 10:26 pm)
Re: [LAD] Mixing audio: Noiseless volume changes, Harry van Haaren, (Tue Mar 19, 1:31 pm)
Re: [LAD] Mixing audio: Noiseless volume changes, Harry van Haaren, (Tue Mar 19, 4:30 am)
Re: [LAD] Mixing audio: Noiseless volume changes, Tim Goetze, (Tue Mar 19, 3:22 am)