[PD] new clear function for delwrite~

IOhannes m zmölnig zmoelnig at iem.at
Fri Oct 20 22:30:41 CEST 2017

On 10/20/2017 07:49 PM, Matt Davey wrote:
> How does the new clear function work for delay lines?
> Is it just zero-ing out the whole delay line with a for loop?

basically yes.
is there anything else that needs to be done?

> Is there a lot of cpu used, for example, to clear a 2 minute delay line?
plenty. miller was very reluctant to add this feature to [delay] exactly
because it breaks realtime safety.

a 2 minute delay line has 5292000 samples (when running at 44.1kHz)
which is 21168000 bytes.
so if deleting a single byte takes a single machine instruction on your
architecture, this would some up 21168000 instructions to be called. on
a decently modern i486 with turbo speed enabled, this might take up to
0.14 seconds. so make sure that you set the audio buffer high enough¹.


¹ on my currently-breaking-apart laptop it takes usually under 3ms; but
this is arcane technology (and judging from the sound of the harddisk
these measurements might be void in a few weeks)

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