[PD-dev] What goes on during dsp ticks?

[PSPunch]

Hi,


I would highly appreciate some assistance in grasping how signals are
processed in DSP objects.


Working on the following template, I will demonstrate variations in the
<PROCESS BLOCK>. As results do not appear as the way I expect, there
must be something I am not understanding correctly.


========== Template ==========

t_int *foobar_tilde_perform(t_int *w)
{
  t_sample  *in  =    (t_sample *)(w[1]);
  t_sample  *out =    (t_sample *)(w[2]);
  int          n =         (int)(w[3]);

  <PROCESS BLOCK>

  return (w+4);
}


=====================
== PROCESS BLOCK.1 ==
=====================

  while (n--) {
	*out++ = *in++;
  }


Remarks: Simple THRU... works as expected.


=====================
== PROCESS BLOCK.2 ==
=====================

  while (n--) {
//	*out++ = *in++;
  }


Remarks: Action is commented out but signal goes through.. Why?


=====================
== PROCESS BLOCK.3 ==
=====================

  while (n--) {
	*out++ = *in++ * -1;
  }


Remarks: Inverse signal, as expected


=====================
== PROCESS BLOCK.4 ==
=====================

  n--;
  *out++ = 0;
  while (n--) {
	*out++ = *in++;
  }


Remarks: Expecting first sample of the block to be zero and others
delayed by 1 sample. Instead, I get an constant output of zero.



I hope what I am missing is something obvious to those with insight.

Thanks.

--
David Shimamoto