Rockbox mail archiveSubject: Re: FS#10199: Limiter DSP function
Re: FS#10199: Limiter DSP function
From: Jeff Goode <jeffg7_at_gmail.com>
Date: Mon, 17 Aug 2009 10:36:16 -0400
Al Le wrote:
> Jeff, I read the patch description and tried to understand what it
> does but couldn't fully do it. (Disclaimer: I'm not a sound processing
> expert.) And I'm sorry for not having replied earlier.
> What I understood from reading the description is that it would have
> an effect as if you manually change the volume so that silent parts of
> the recording are loud but loud parts of it don't blow your ears. Is
> it a correct description? Of course, this volume adjustment is made
> automatically. What scenarios is this thought for? Because this would
> distort the song. Is it for text only "songs"?
I envisioned a use for listening to dynamic material in noisy
environments, i.e. material that is well-mastered, not overly compressed
as most modern discs are. Most of time you wouldn't need it, since a
lot of the time the mastering engineer is making it iPod friendly.
(That's not praise for the practice, BTW). But with dynamic material,
this function does on the fly what loudness warrior engineers do in the
studio: it crushes dynamic range to make the material more audible - and
seem louder overall.
> And how would you need to set the volume manually (before you start
> the playback)? I see two possibilities:
> 1. set it so that the silent parts are at desired volume, and the loud
> parts are made more quiet
> 2. Set it so that loud parts are at desired volume, and the silent
> parts are automatically made louder.
That's entirely up to you. The main volume control isn't affected. In
fact, the maximum available volume isn't raised either. It's just that
the quieter material is preferentially increased in amplitude and the
louder material is crushed against the clipping limit. If you want to
increase apparent loudness, increase the preamp and leave the volume
alone. If you want a "night mode" scenario, then increase the preamp
and turn down the master volume the same amount. That has the effect of
reducing the clipping limit (and reducing peaks) and leaves the quiet
Received on 2009-08-17