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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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March 18, 2013 06:47:16 PM you wrote:
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n Mon, Mar 18, 2013 at 5:50 PM, Tim E. Real <termtech@rogers.com> wrote:

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i again. Looking for any advice, tips, tricks, anecdotes etc.I want to eliminate or reduce 'zipper' noise on volume changes.=

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