Re: [LAD] Mixing audio: Noiseless volume changes

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To: <linux-audio-dev@...>
Date: Monday, March 18, 2013 - 11:05 pm

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On March 18, 2013 06:47:16 PM you wrote:

On Mon, Mar 18, 2013 at 5:50 PM, Tim E. Real 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
from 0.0 to 1.0, if I limit the slew rate to say 0.01 per sample then after
100 samples the ramp will be done.
But even with a fine ramp, this still might introduce artifacts in the audio.

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

Wow, surprising answer.
Can you elaborate a wee bit on the bogus point? What worse artifacts?
Popping noise will be heard if sudden volume change is applied while
the signal data value is currently non-zero.
Is it not better to apply (register) the changes during zero or near-zero
signal data values?

After all, some electronic systems employ it:
http://en.wikipedia.org/wiki/Zero_crossing
http://electronicdesign.com/analog/digital-volume-control-eliminates-zip...
noise

Thanks.
Tim.
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On =
March 18, 2013 06:47:16 PM you wrote:

O=
n Mon, Mar 18, 2013 at 5:50 PM, Tim E. Real <termtech@rogers.com> wrote:
H=
i 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 signa=
l detection, and slew-rate limiting.Code is almost done, almost r=
eady to start testing each technique.Each technique has some adva=
ntages and disadvantages.If I use a slew-rate limiter, I fi=
gure for a sudden volume factor change=A0from 0.0 to 1.0, if I li=
mit the slew rate to say 0.01 per sample then after=A0100 samples=
the ramp will be done.But even with a fine ramp, this still migh=
t introduce artifacts in the audio.
<=
br />You cannot avoid artifacts in the audio. The only question is what=
is the nature of the artifacts. =A0
=A0=

I=
f I use a zero-crossing/zero-value detector and apply volume changes
<=
br />Zero crossing stuff is a completely bogus idea that needs to be el=
iminated from the lexicon of audio software. You will not be accomplish=
ing anything trying to use such a technique, other than introduce even =
more artifacts (and rather horrendous ones at that). Even zero-valued s=
amples are not particularly useful - keep in mind that what defines tra=
nsducer (read: speaker) behaviour is power, not instantaneous volume.=A0=
Just use sensibly short ramped changes. For the record, Ar=
dour uses 64 or a JACK period size, whichever is, hmm, larger or smalle=
r, can't recall.--p
Wow=
, surprising answer.
Can=
you elaborate a wee bit on the bogus point? What worse artifacts?
Pop=
ping noise will be heard if sudden volume change is applied while
th=
e signal data value is currently non-zero.
Is =
it not better to apply (register) the changes during zero or near-zero<=
/p>
si=
gnal data values?
 
Aft=
er all, some electronic systems employ it: http://en.wikipedia.or=
g/wiki/Zero_crossing
htt=
p://electronicdesign.com/analog/digital-volume-control-eliminates-zippe=
r-noise
Tha=
nks.
Tim=
.
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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)