You're totally right that the sentence >The delay time is always at least one sample and at most the length of the delay line (specified by the delwrite~)< is misleading.

But the reason why it can't be exactly the length of the delay line is quite simple: Because in Pd audio is computed in blocks, the [delwrite~] is actually updated every M samples, where M is the blocksize of the subpatch where the [delwrite~] is located. [delread~] and [vd~] always get the N last samples of the delay line, starting from the index you're sending to the object, where N is the blocksize of the subpatch where the reading object is located. So if the reading index would be exactly at the last sample, you could only read that single sample for the whole block.

BTW: There's a funny issue when the blocksize of the [delread~] is smaller than the blocksize of the [delwrite~]: In that case the [delread~] is reading more often than the delay line itself is actually updated, so you get repetitions of blocks.

> actually, I made some tests and it is the (buffersize - windows size + one block 0f 64 samples).

Are you sure? Maybe it only appears like that because there's an inherent 'delay' of 64 samples between a parent patch of bocksize 64 and a subpatch with a higher blocksize. I should do some testing about that.

Gesendet: Montag, 21. September 2015 um 23:05 Uhr
Von: "Alexandre Torres Porres" <porres@gmail.com>
An: "Christof Ressi" <christof.ressi@gmx.at>, "Miller Puckette" <mpuckett@imusic1.ucsd.edu>, "pd-list@lists.iem.at" <pd-list@lists.iem.at>
Betreff: Delay time limit bug (was: PVoc patch "bug"?)

> the actual limit of the delay line is the buffersize minus the windows size

actually, I made some tests and it is the (buffersize - windows size + one block 0f 64 samples).

But anyway, this limitation is what I perceived, but I fail to see why any such limitation should happen. If the delay is "x" long, we should be able to read from "x" behind in time... if not, there's a bug in it. That's how I see it, and why I marked this issue as a potential bug.

From the [vd~] help file, it says

"The delay time is always at least one sample and at most the length of the delay line (specified by the delwrite~)"

So if we can't read it at most from the specified delay line, there's a bug!

> since the delay line is only written for every block and you want to read

> the last N samples from the delay line, [vd~] simply clips to the

> maximum reading index.

Again, I fail to see a reason here. If such a limitation happens, maybe the object could be coded in a way that it allows an extra something to make it possible a total length read out.

But I thought that maybe the order forcing of delay objects could be something to take into consideration. Well, I did the order forcing and many such tests, but nothing really changed!

I have then the latest version attached. I'm copying miller here and also sending to the list. I'll also post this as a bug report.

cheers

2015-09-21 16:45 GMT-03:00 Christof Ressi <christof.ressi@gmx.at>:

Hey, as I suspected, you are simply hitting the limit of the delay line. You can test this on your own with the patch I've sent you. Note that the actual limit of the delay line is the buffersize minus the windows size, since the delay line is only written for every block and you want to read the last N samples from the delay line. [vd~] simply clips to the maximum reading index. Note that there isn't any phase difference anymore between the two windows after both have exceeded the limit.

Cheers

Gesendet: Montag, 21. September 2015 um 19:53 Uhr
Von: "Alexandre Torres Porres" <porres@gmail.com>
An: "Christof Ressi" <christof.ressi@gmx.at>, "pd-list@lists.iem.at" <pd-list@lists.iem.at>
Betreff: Re: Re: PVoc patch "bug"?

I've simplified the patch a lot so many things can be discarded.

The window size shouldn't affect anything as the reading point in the delay line is fixed. Now I don't have [vline~] or anything, just a steady signal fed to [vd~], when we get close to the end of the delay line it just gets ruined, and that's all that there is to it. There's no flaw in the patch, nothing I didn't think of. It's really something very mysterious or perhaps a bug.

The patch is now simpler and also vanilla compatible. I tried it in the new Pd Vanilla 0.46-7 and I got the same weird behaviour.

Check attachment please

cheers

2015-09-21 14:12 GMT-03:00 Christof Ressi <christof.ressi@gmx.at>:

Well, I just think you're hitting the limit of the delay line. Your window size is 2048 samples, so inside the subpatch that's 2048/(44,1*4) = 11,6 ms. But one window is one hop size (2,9 ms) behind, therefore 11,6 ms + 2,9 ms = 14,5 ms and 1000 ms - 14,5 ms = 985,5 ms --> that's pretty much the limit you were experiencing. Hope that helps.

Cheers

Gesendet: Montag, 21. September 2015 um 18:27 Uhr
Von: "Alexandre Torres Porres" <porres@gmail.com>
An: "Christof Ressi" <christof.ressi@gmx.at>, "pd-list@lists.iem.at" <pd-list@lists.iem.at>
Betreff: Re: PVoc patch "bug"?

my patch has a little issue, I'm saying the delay line is 60000 ms (this is for the wrapping objects) when it's only 4000, but that is not a problem for what I'm asking here as the wrapping doesn't influence anything. It's just something weird that happens even without the wrapping.

I wonder what's the principle you'd have for not using cyclone :)

2015-09-21 12:32 GMT-03:00 Christof Ressi <christof.ressi@gmx.at>:

Hey,

the first thing I noticed: your [delwrite~] is at 4000 ms, but [s $0-buff_size] is still fed with 60000 ms... Is this on purpose?

The second thing: Even if you got the range for [pong~] right, my guess is that this will create a sudden jump from the end of the delay line to the beginning. You'd need some kind of enveloping to mask the discontinuity. Maybe this won't be noticeable if you pass the 'problematic' area quickly, but might sound terrible if you stay there. In your case, however, it seems that the delay line is simply clipped since you've sent a wrong value to [pong~].

This is just some remote diagnostics, though, since I don't use any cyclone objects as a matter of principle :-D.

Cheers

PS: I didn't put this on the list on purpose, because it's only about a specific patch and not something more general.

Gesendet: Montag, 21. September 2015 um 06:48 Uhr
Von: "Alexandre Torres Porres" <porres@gmail.com>
An: "pd-list@lists.iem.at" <pd-list@lists.iem.at>, "Christof Ressi" <christof.ressi@gmx.at>
Betreff: PVoc patch "bug"?

Hi there, still struggling with my circular buffer Phase Vocoder, now I've found an issue that has no apparent reason.

Check the attached patch please

the speed is 100% and pitcnh shift is "0", so the signal from vline~ stands still in one particular point in the buffer (read from [vd~]).

buffer size is 4000 ms, into the PVoc subpatch is supposed to be "1000" for it does oversampling with the overlap of 4 (we've discussed this before). Anyway, I'm using sampstoms~ and mstosamps~ to convert in a way that works for the patch.

The point is, when getting close to the end of the delay line, things get ruined for no reason! The end of the buffer is 1000 ms, not 4000 ms as pointed above. You can check my patch and see how that goes.

If the reading point is at somewhere just after the buffer size less a window size plus a hop size (around 985 ms) things get bad.

I can't find a reason for that in a million years. Please help

thanks