[PD] headroom in Pd

[peiman khosravi]

However, it's probably wise to clip the signal before sending it to dac~.
Entirely for health and safety reasons!




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On 21 December 2013 13:48, IOhannes m zmölnig <zmoelnig at iem.at> wrote:

> On 2013-12-20 23:34, Martin Peach wrote:
> > On 2013-12-20 16:55, Alexandre Torres Porres wrote:
> >> Hi there, where can I find info about headroom and clipping on Pd. Or
> >> can anyone tell me quickly how it goes?
> >>
> >> Does it always really clip over a maximum of 1, or is there some
> >> headroom? Does it depend on the audiocard or something?
> >
> > The soundcard will always clip above +1 and below -1, and sometimes even
>
> yes, but the output of Pd (what you send to [dac~]) is not necessarily
> sent directly to the soundcard: e.g when using jack, the samples will be
> passed as floating point values to the next client: so samples exceeding
> -1..+1 need not clip at all.
> you can confirm this by connecting the output of Pd to the input of Pd
> via jack, and send a [osc~ 440]*10 ...
>
> but when you connect this output to the system output, you will get
> clipping.
>
> afaik, you get something similar on OSX, where the (portaudio) API will
> take floating point samples, and the signal gets sent through a limiter
> to prevent obvious clipping.
>
> so the bottom line is: hardware always has a physical range limit (that
> is mapped to -1..+1).
> but Pd is software and some audio APIs can handle sample values in
> floating point format just fine. with these, you most likely don't get
> any *immediate* problems if the range exceeds -1..+1.
> however, how excessive samples are handled is highly depending on the
> audio API and eventually other components in the signal chain.
> so if you do want to output signals that are outside -1..+1, you are on
> your own (from Pd's perspective).
>
>
> > within those limits (if the interpolated waveform between samples goes
> > over the limit).
>
> well, the reconstruction filters in the DAC won't necessarily clip in
> this case.
>
>
> gfamdsr
> IOhannes
>
>
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