Re: [linux-audio-dev] Paper on dynamic range compression

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To: The Linux Audio Developers' Mailing List <linux-audio-dev@...>
Date: Wednesday, October 18, 2006 - 12:02 pm

On Wed, Oct 18, 2006 at 10:45:02AM +0100, Steve Harris wrote:

I was referring to aliasing in the compressed audio. Harmonic distortion
is introduced during the attack (and decay, but usually to a lesser extent
because it's slower).

Consider a sine wave audio input. In the attack, the gain is decreasing,
so the rising parts of each input half-cycle are reduced in slope, and
the falling parts are increased in slope. The audio waveform starts to take
on a sawtooth shape if the rate of gain change is high enough.

This is a form of harmonic distortion and happens with any compressor,
analog or digital. In a digital compressor aliasing will occur if the sample
frequency is insufficient to deal with the introduced harmonics (which
have been added _inside_ the digital domain remember, so no amount
of anti-aliasing filtering on an input ADC will have any effect on it).
It will only last for the duration of the attack/decay, but that doesn't
make it inaudible. A small amount of harmonic distortion on its own is not
objectionable, but when it is accompanied by aliasing it's bad news.

John

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Messages in current thread:
[linux-audio-dev] Paper on dynamic range compression, Andres Cabrera, (Thu Oct 5, 3:50 am)
Re: [linux-audio-dev] Paper on dynamic range compression, Alfons Adriaensen, (Thu Oct 5, 8:46 am)
Re: [linux-audio-dev] Paper on dynamic range compression, Andres Cabrera, (Thu Oct 5, 1:44 pm)
Re: [linux-audio-dev] Paper on dynamic range compression, Andres Cabrera, (Thu Oct 5, 2:01 pm)
Re: [linux-audio-dev] Paper on dynamic range compression, Andres Cabrera, (Fri Oct 6, 2:25 am)
Re: [linux-audio-dev] Paper on dynamic range compression, Andres Cabrera, (Thu Oct 5, 2:14 pm)
Re: [linux-audio-dev] Paper on dynamic range compression, Alfons Adriaensen, (Thu Oct 5, 3:29 pm)
Re: [linux-audio-dev] Paper on dynamic range compression, Andres Cabrera, (Fri Oct 6, 2:48 am)
Re: [linux-audio-dev] Paper on dynamic range compression, Fons Adriaensen, (Thu Oct 5, 5:05 pm)
Re: [linux-audio-dev] Paper on dynamic range compression, Erik de Castro Lopo, (Tue Oct 17, 9:18 pm)
Re: [linux-audio-dev] Paper on dynamic range compression, Erik de Castro Lopo, (Tue Oct 17, 10:28 pm)
Re: [linux-audio-dev] Paper on dynamic range compression, Jens M Andreasen, (Wed Oct 18, 5:23 am)
Re: [linux-audio-dev] Paper on dynamic range compression, Erik de Castro Lopo, (Wed Oct 18, 8:50 am)
Re: [linux-audio-dev] Paper on dynamic range compression, Fons Adriaensen, (Wed Oct 18, 11:33 am)
Re: [linux-audio-dev] Paper on dynamic range compression, Fons Adriaensen, (Wed Oct 18, 4:35 pm)
Re: [linux-audio-dev] Paper on dynamic range compression, Erik de Castro Lopo, (Wed Oct 18, 11:21 am)
Re: [linux-audio-dev] Paper on dynamic range compression, Steve Harris, (Wed Oct 18, 11:08 am)
Re: [linux-audio-dev] Paper on dynamic range compression, Steve Harris, (Wed Oct 18, 10:42 am)
Re: [linux-audio-dev] Paper on dynamic range compression, Paul Winkler, (Tue Oct 17, 11:00 pm)
Re: [linux-audio-dev] Paper on dynamic range compression, Steve Harris, (Wed Oct 18, 10:58 am)
Re: [linux-audio-dev] Paper on dynamic range compression, Fons Adriaensen, (Tue Oct 17, 9:54 am)
Re: [linux-audio-dev] Paper on dynamic range compression, Fons Adriaensen, (Tue Oct 17, 2:41 pm)
Re: [linux-audio-dev] Paper on dynamic range compression, David Olofson, (Tue Oct 17, 4:51 pm)
Re: [linux-audio-dev] Paper on dynamic range compression, Fons Adriaensen, (Tue Oct 17, 5:05 pm)
Re: [linux-audio-dev] Paper on dynamic range compression, John Rigg, (Wed Oct 18, 12:02 pm)
Re: [linux-audio-dev] Paper on dynamic range compression, Dominique Michel, (Wed Oct 18, 3:40 pm)
Re: [linux-audio-dev] Paper on dynamic range compression, Steve Harris, (Wed Oct 18, 10:54 am)
Re: [linux-audio-dev] Paper on dynamic range compression, Steve Harris, (Tue Oct 17, 12:06 pm)
Re: [linux-audio-dev] Paper on dynamic range compression, Alfons Adriaensen, (Fri Oct 6, 9:00 am)
Re: [linux-audio-dev] Paper on dynamic range compression, Alfons Adriaensen, (Thu Oct 5, 2:22 pm)
Re: [linux-audio-dev] Paper on dynamic range compression, Andres Cabrera, (Fri Oct 6, 3:47 am)
Re: [linux-audio-dev] Paper on dynamic range compression, Andres Cabrera, (Fri Oct 6, 2:31 pm)