[PD] headroom in Pd

Miller Puckette msp at ucsd.edu
Sun Dec 29 18:42:00 CET 2013


This is frightening - if I were a musician reading this I'd be frightened
to ever use Appe software in a serious project.

(Of course, we do't know what happens in Windows under the hood either.  The
only way you can truly know what you're getting is to use an open-source
OS.

cheers
Miller

On Sun, Dec 29, 2013 at 12:12:04PM -0500, Martin Peach wrote:
> 
> On 2013-12-29 10:08, Alexandre Torres Porres wrote:
> >here's the deal, if I have a square wave in Pd running at 1 -1 peak to
> >peak, then you say that should be my maximum output, right?
> >
> >Thing is that if I give it an extra boost (say, multiply it by 2) I
> >can clearly listen an increase in loudness. Hence, something in my
> >system is allowing some headroom to be output.
> >
> >I got a macbook air from 2010 running 10.7.5... if Pd is not
> >responsible for this, maybe my hardware + Mac OS is?
> >
> 
> Yes it's a Mac-specific issue. On Win7 I get no difference above 1.0.
> The Apple audio driver is responsible for "clipping" values outside
> of [-1.0..1.0] as they arrive from possibly multiple applications.
> The docs state that clipping can be done in a "soft" way, so I
> suspect that the default driver (for the headphone output) is doing
> some sort of compression. Possibly if you use an external interface
> this won't happen (?).
> 
> (see for example https://developer.apple.com/library/mac/documentation/DeviceDrivers/Conceptual/WritingAudioDrivers/ImplementDriver/ImplementDriver.html#//apple_ref/doc/uid/TP30000732-BAJCBIAF
> )
> Martin
> 
> 
> >here's the patch, try yourselves and tell me what you get please.
> >
> >Cheers
> >
> >
> >#N canvas 653 26 257 182 10;
> >#X obj 79 97 dac~;
> >#X obj 85 41 square~ 440;
> >#X floatatom 125 72 5 0 0 0 - - -;
> >#X obj 85 70 *~;
> >#X connect 1 0 3 0;
> >#X connect 2 0 3 1;
> >#X connect 3 0 0 0;
> >#X connect 3 0 0 1;
> >
> >2013/12/21, IOhannes m zmölnig <zmoelnig at iem.at>:
> >>On 2013-12-21 14:58, peiman khosravi wrote:
> >>>However, it's probably wise to clip the signal before sending it to dac~.
> >>>Entirely for health and safety reasons!
> >>
> >>this really depends...a clipping sine will have loads of high
> >>frequencies that might be equally damaging to your audience.
> >>
> >>if you want to be safe, use math to make sure that your signal won't
> >>exceed -1..+1 before sending to the [dac~].
> >>
> >>or use a limiter (zexy has a handy one).
> >>
> >>fgmrdsa
> >>IOhannes
> >>
> >>
> >
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> >
> 
> 
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