Re: [LAD] Mixing audio: Noiseless volume changes

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To: <linux-audio-dev@...>
Date: Tuesday, March 19, 2013 - 3:08 pm

On Tue, Mar 19, 2013 at 03:02:19PM +0100, Tim Goetze wrote:

> > for (i = 0; i < nframes; i++)

Yes. In this case it's possible to remove one multiplication:

a = 0.07f;
b = 1 + a;

// ...

gm = b * gt;
for (i = 0; i < nframes; i++)
{
g1 += w * (gm - g1 - a * g2);
g2 += w * (g1 - g2);
out [i] = g2 * in [i];
}

But CPU usage is not the point. For a biquad the result
can depend on small differences between the coefficients,
with consequent loss of precision. It's a problem mainly
with LF filters. Try a 10 Hz highpass at 96 kHz.

Ciao,

--
FA

A world of exhaustive, reliable metadata would be an utopia.
It's also a pipe-dream, founded on self-delusion, nerd hubris
and hysterically inflated market opportunities. (Cory Doctorow)

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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)