Hello! I'm new here and I'm a Pure Data beginner. I'm stuck with an issue that I can't resolve, maybe someone could help me! I'd like to control a Stereo Delay effecting an audio file in real time with knobs (ctlin 34) but when I change the amount of Time Delay I hear some clicks/steps. I tried somehow to use a (line) object but I failed...

Thanks a lot, Leila.

@Zooquest You will hear clicks because there will be jumps between samples.... if the playback was at a sample level of 0 and you change the delay time to a point where the level is 1 then the click will be loud.
You will hear "steps" as the playback point is probably being changed repeatedly by the ctrl messages.

You could experiment with a [lop~] filter in the delayed sound output, with a high value e.g... [lop~ 5000] but you will lose some high frequencies in the echo.
That might sound natural though, like an old tape echo, but you will probably still hear the clicks a little.

Or you could "duck" the echoes by not changing the delay time immediately, reducing the echo volume to zero in say 3msecs using using [vline~] and not bringing the echo volume back up to 1 (in, say, 3msecs again) until you have NOT received a ctrl message to change the delay time...... for again 3msecs.
The last part of that would need a [delay 3] using the property that any new bang arriving at its inlet will cancel the previously scheduled bang.

You would need to duck the FB signal as well though, and all that that might sound worse than the [lop~].

I cannot remember well...... but this "sampler_1.pd" might contain elements useful to demonstrate "ducking" https://forum.pdpatchrepo.info/topic/13641/best-way-to-avoid-clicks-tabread4/12

Or do a crossfade between separate delays once the incoming control messages have stopped..... https://forum.pdpatchrepo.info/topic/12357/smooth-delay-line-change-without-artifacts ..... as you can then avoid the "duck"ing effect.
David.

@whale-av thanks a lot! I tried the [lop~] but as you said I still hear the clicks, so I will try the crossfade. I'd really like to re-create the stompbox delay/echo effect: send a short sound and change the delay time fast, with feedback

If you prefer the simple approach with doppler,
try to slow down too sudden changes in delay-time
for example like this:

[ctlin]
|
[* 7.8]
|
[sig~]
|
[lop~ 0.5]
|
[delread~]

Additionally you can reduce artefacts (the sizzle, not the doppler) of fast (but not immediate) changes by upsampling the delayline.
I think the sizzle is ether caused by aliasing or a combination of interpolation artefacts with aliasing.

thanks @lacuna I tried your solution but [delread~] doesn't accepts audio signal, right?
How can I try to upsample the delayline?

@Zooquest [unsig~] from the iemlib library will convert audio to control rate...
It's an abstraction..... just a [metro] and [snapshot~]......
unsig~.pd
unsig~-help.pd

But [delread4~] will read from the [delwrite~] buffer, and take an audio signal as a delay control, and it also interpolates.
In older versions of Pd it was named [vd~]

@lacuna's post will slow the rate of change of the delay time...... https://forum.pdpatchrepo.info/topic/11850/explanation-for-lop-object-in-this-patch-requested

David.

yes, sorry, mistake in a rush, meant to use [delread4~] as it 4-point interpolates between samples. Sorry for distraction,

Don't use control-rate here.
It is audio being continously and smoothly modulated in signal-rate.
Could be done with [vline~] somehow, but imho more complicated than [sig~] and [lop~] (<---play with it's cuttoff frequency)

slow the rate of change of the delay time...... https://forum.pdpatchrepo.info/topic/11850/explanation-for-lop-object-in-this-patch-requested

this

( And slightly offtopic, because it is not about the clicks you heared in your patch (caused by sudden jumps in the delay-line) :

How can I try to upsample the delayline?

Try the patch, does this sound like what you where looking for?
And if there is sizzle in the highs, you want to clean, you can try to upsample.
See
help > helpbrowser > puredata > 3.Audio.examples > J07.oversampling

Put [delwrite~] and [delread4~] in a [pd subpatch] with [inlet~ lin] and [block~ 64 1 16] and an anti-aliasing filter as shown in J07.oversampling )

@Zooquest said:

I'd really like to re-create the stompbox delay/echo effect: send a short sound and change the delay time fast, with feedback

Does that change the pitch on a stomp box?
If it does then this might be better.... https://forum.pdpatchrepo.info/topic/13234/tape-loop-effect/8 ... although it needs to be run in Pd 0.47 (32-bit for [ipoke~] and with [text] built-in) unless you can build a 64-bit [ipoke~] for your system.
The other option is to use @jameslo's 64 bit virtual ipoke~ which I have added to the bottom of that thread, on an up-to-date version of Pd.
But that might bring the clicks back.
David.