[PD] How does vline~ work under the hood?

[Matt Barber]

It'll have more to do with how large the increment is, and what an
increment means psychoacoustically. If you ramp over the range of a piano
in pitch over a second, incrementing every 64 samples, each increment will
be about 12.5¢, which is likely to be audible. Or if you ramped from 20hz
to 20khz in frequency, you'd be adding some 28hz per increment, which is a
lot of pitch at the low end.
Doesn't the audibility of zipper noise depend on the duration of the ramp?

I seem to remember some Supercollider tutorials that used Line.kr with
a duration of a second or so, and I don't remember hearing zipper noise.
(Also
made a little Pd demo using [bang~] and a counter, but I don't know what I
did with it.)

-Jonathan



On Friday, October 2, 2015 7:41 PM, Matt Barber <brbrofsvl at gmail.com> wrote:


You'll get zipper noise with the samphold per block approach.
Cost to dereference a struct member is probably a little more than just
using or getting a value. It's possible it'll be cached, though.
On Oct 2, 2015 5:26 PM, "Jonathan Wilkes via Pd-list" <pd-list at lists.iem.at>
wrote:

There are probably a lot more ways to implement ramps.  For example, you
could increment only at block boundaries and just repeat that value for the
rest of the block.  That would looks a lot like Supercollider's "kr"
ugens.  (I
actually thought that's how [line~] worked until I looked at the code.)

Btw-- does it cost anything significant to dereference x->x_inc inside the
while loop of line_tilde_perform?  Or is the compiler able to somehow
optimize that?

-Jonathan



On Friday, October 2, 2015 11:36 AM, i go bananas <hard.off at gmail.com>
wrote:


Hi, me again.

Thanks for the discussion.  It has really opened my eyes.

So, i got my naive c++ implementation of line~ basically working.

And of course, just running a for loop incrementing by ticks, i run into
the exact precision error that this block quantizing seems to avoid.  My
line from 0 to 100 over 44100 samples only gets to 99.93

So, i also need to add something like pd's block quantization to make sure
my line goes all the way to the specified value.

My questions then are 2:

Is pd's method the way i should do it?  Or is there a better alternative?

And, if i do it the pd way, how does that work?  Does the increment get
updated every block?   Or is it just the last block that is stretched?



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