[PD] ring buffer with an array

Alexandre Torres Porres porres at gmail.com
Mon Jan 9 00:10:06 CET 2012

Well, this is for the phase vocoder patch, which is based on miller's I07

There's a counter that reads over the table, and I expanded the thing
allowing it to loop and other convenient sampling controls.

I never needed a perfect loop, cause I never loaded real perfectly looped
files in it, so I just check when the counter grows bigger than the table
size and restart it. As for recording on the tables, I do fade-in and
fade-out, because it would click anyway.

Now, for the ring buffer, it needs to be in perfect sync, so I can have
tables that are multiples of the block size and use [bang~], it's not that
much of a big restrain at all. You won't be able to specify an exact table
size, but the resolution is 64 samples, and that is like 1.45 miliseconds
(about nothing). So I got over it, did it, and it works!!!

I can adapt the thing for loaded samples, and have it the table size
rounded up to multiples of the block + 1. This is not a perfect loop, but
they weren't perfect before anyhow...

But why stop there? How to make it loop perfectly? This is the issue
now. *Checking
Miller's Phase Vocoder example. If you load a sample, how to make it loop

I know one could use phasor~ and other stuff to read the table. But for the
Phase Vocoder patch, we need that structure with the counter and everything.

Well, I'll keep thinking.


2012/1/8 Charles Henry <czhenry at gmail.com>

> On 1/8/12, Alexandre Torres Porres <porres at gmail.com> wrote:
> > Hi folks, I'm trying to implement a ring buffer with a table for a
> sampler
> > patch based on an array.
> >
> > But I'm having the hardest time cause it always "clicks" when I start
> > writing back on the beginning of the array.
> >
> > I made this simple test attached below using metro. But I'm figuring the
> > flaw is because is not trivial at all to keep control data in sync with
> > audio blocks
> >
> > any hints or ideas?
> I think you might be better able to keep the data in sync with a
> vline~/metro/tabread4~ construction, because it preserves the timing
> information in the messages.  Instead of vline~/metro, you could also
> use phasor~ which makes the looping implicit.
> To work around clicks, crossfading is what I hear about the most on
> list.  I'm not sure how it's implemented.
> When I think about coding in C, I always want to have N contiguous
> samples to avoid having to check against the end of the array.  To do
> that, you make the buffer 2*N-1 in length.  Then, on each write, you
> write to two locations (0,N), (1,N+1), (2,N+2)...  That ensures there
> is always N samples in a row to read from, and you just move the read
> pointer by 1 each time you get a vector of N samples long. (my
> personal method...nothing more).
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