[PD-dev] dynamic patching - is iemguts the way to go?

[Nick Porcaro]

Hi Miller-

> On Aug 20, 2019, at 7:08 PM, Miller Puckette <msp at ucsd.edu <mailto:msp at ucsd.edu>> wrote:
> 
> actually I wrote that before I thought the whole thing out :)
> 
> No, if you "tick" a pdlib instance you tick all the patches in it - so teh
> way to get different patches in different orders is to call up a separate
> Pd instance for each of them, and use "adc~" and "dac~" objects to get
> audio in and out - that incurs zero latency (once you've buffered 64
> samples in the first place).

I tried this two ways:  

- Create separate Pd  instances for each patch wrapped in adc~ and dac~

- Use a single Pd  instance with multiple patches,  with each patch wrapped in adc~ and dac~

Then I have a simple JUCE app (based on the sampler example) that drives
these pd patches.

There is no problem with doing switch~ and such, but I am 
getting distortion that seems like clipping in both cases (one pd instance with many patches
or multiple pd instances with one patch)

To be more clear these wrapper patches are like:

Patch 1:     [adc~]   ->   [lop~ 200] -> [dac~]
Patch 2:     [adc~]   ->   [hip~ 200] -> [dac~]

These wrapper patches also have a loadbang to pd dsp 1;

Then the code that calls these patches does something like this calling libpd:

for (each buffer from the audio callback) {
    for (a smaller buffer that’s the pd block size (eg 64)) {
        pd->processFloat (oneTick, smallBufferIn, smallBufferOut);
  }
}

I tried scaling the input and output to these  wrapper patches after the adc~ and before the dac~
and that does not solve the distortion/clipping problem either.

There are a couple of more things I can try:

   - make the wrapper patches even simpler, just scaling instead of the filters.
   - dump the samples to a file and maybe that will shed some light on the problem.
   - making a much simpler example program that I can share will you all.

I have libpd and pd source directly compiled into my example

Any other ideas would be greatly appreciated!


> 
> OR, within one pd instance, in libpd or in Pd, you can use switch~ objects,
> switched off, to control each sub-patch.  Send the switch~ objects bangs in
> whatever orders you wish.  In this scenario, tabsend~ and tabreceive~ would
> be the simplemt way to pass signals between them.  In libpd you can do this
> zero-latency (just stuff your inpuits into arrays before sending all the
> tick messages and copy the results out afterward).

This approach works well, but the problem is I can’t insert non-Pd signal processing
anywhere I’d like in the Pd patch so that’s why I went with the first approach.

> 
> Within the Pd app, you can do teh same thing but you incur one tick extra
> latency, because copying the autio into the tables has to happen on the
> previous tick form the one on which you get the outputs back.
> 
> If you like danger, you can write an external tilde object that, for its
> "dsp" action, sends a message to teh patch that can "tick" the switch~
> objects right in the middle of Pd/s DSP tick.  This is not part of Pd
> because it could cause major confusion if general-purpose Pd messages
> got sent around in mid-tick.
> 
> cheers
> Miller
> 
> On Tue, Aug 20, 2019 at 11:55:58PM +0200, Roman Haefeli wrote:
>> On Tue, 2019-08-20 at 12:09 -0700, Miller Puckette wrote:
>>> I think the way to do this in libpd is to open them all as separate
>>> patches
>>> within one instance of Pd (so that symbols are shared) and use
>>> "tabsend"
>>> and "tabreceive" to route signals to/from them, using shared names
>>> like
>>> "channel1" as both inputs and outputs so you can rearrange them in
>>> any
>>> order.
>>> 
>>> (Beware of allowing patches to _write_ andy of their output channels
>>> before
>>> reading all the input channels, if you're re-using the same channels
>>> as 
>>> inputs and outputs :)
>> 
>> Do I understand right: When loading them as separate patches, you can
>> dynamically re-order the signal flow by using [tabsend~]/[tabreceive~]
>> (which you could with abstractions, too) _without_ adding latency?
>> 
>> And: When changing the symbol of [tabsend~] or [tabreceive~], is the
>> DSP graph re-calculated?
>> 
>> Roman
> 
> 
> 
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