[PD] making puredata headphone-safe

[Ed Kelly]

Ah, guilty as charged.


Those LPC plugins don't work very well due to discuntinuities in the filter kernel across DSP block boundaries. It has been on my to-do list for a very long time to recode those objects using a different method. One way to guarantee that things will screw up is to change the number of poles rapidly.
The problem is that some objects can generate unstable errors that are orders of magnitude greater than normal audio signals. Then there is a signal that maybe goes between +/- 100000 rather than +/- 1, and the volume control makes little difference. Please don't ask me for specific instances - I can't remember any at the moment, but it's happened to me before.

I personally do not use PD with headphones unless it is a patch I know well, with reliable outputs.
Conversely, a lot of "noise" music created using PD is played permanently clipped to oblivion.


One thing you can do is to use a limiter before the dac~. If the problem persists then avoid this plugin.

The metastudio has lots of these. A limited volume control for stereo is enclosed (check the "limit" box, or send a [limit 1( message into the right inlet). 


Best wishes,
Ed Kelly


> On 2011-08-29 11:52, Hans-Christoph Steiner wrote:

>> 
>> On Aug 23, 2011, at 3:43 PM, Martin wrote:
>> 
>>> On 23/08/11 03:29 PM, Stephen Lavelle wrote:
>>>> I've managed to hurt my ears twice over the past two days when using
>>>> PD w/ headphones. Even at lowest system volumes, it seems that
>>>> Terrible Things can happen. Are there any precautions that I can take
>>>> to make it feel less like I'm taking my life into my hands when I
>>>> have to use headphones?
>>>> 
>>>> 
>>>> 
>>> 
>>> Try making a [noise~] connected directly to a [dac~] and set the
>>> headphone volume so you can live with that. Nothing will ever be
>>> louder than that.
>> 
>> 
>> Hmm, I don't think that's actually true in all cases. On a MacBook Pro
>> running Mac OS X, I've had the volume set to one above mute, but had
>> massive feedback from LPC patches that were very very loud. [noise~]
>> would be very comfortable at that volume setting. I think some platforms
>> do the output mixing in the digital domain, so my min volume would be
>> [*~ 0.01], so that this would still make a very loud sound:
>> 
>> [noise~]
>> |
>> [*~ 999999]
>> |
>> [*~ 0.01] (i.e. the Apple output mixing)
>> |
>> 
>> In this particular case, the sound output actually gets shutdown
>> entirely, so you have to reboot to get sound output again.
>> 
> 
> That make no sense. How can you have two sounds at the same level going into a mixer that come out at different levels? Or do you mean that a squealing sound is perceived to be louder than white noise? Maybe you could demonstrate with a patch?
> 
> Martin
> 
> "If it seems like magic your assumptions are wrong." Martin Peach

>I am taking a biologist's approach here: I've observed this happening multiple times in the wild, now I have to figure out why.  Its very reproducible, I've taken the 

>field mice into the lab and seen them reproduce ;)  Take Ed Kelly's fun LPC cross-synth example, in ekext/examples/lpc-cross-synthesis.pd.  Put some loud samples 

>into it and go crazy with the parameters and... MELTDOWN!  I've never heard my computer make a louder sound...  I knew that this patch has some feedback 

>aspect to it, so I was doing my standard practice, having the volume very low.

>.hc

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