[PD] Delay time limit bug (was: PVoc patch "bug"?)

[Alexandre Torres Porres]

2015-09-22 5:56 GMT-03:00 Christof Ressi <christof.ressi at gmx.at>:

> 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.
>

well, I still consider it to be a bug, it's not that it is misleading, it
is just not happening because of bug. There's nothing to prevent you from
reading a delay line to the maximum of what it was specified, if it can't,
then the object is buggy. If it has some limitation of a block less or so,
then there's a simple way to fix it, just add an extra block to the delay
line and make it work. Anyway, I filed this as a bug report yesterday, I
hope it gets checked upon soon, hopefully it'll work for the next Pd
release (0.47).



> 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.
>

Again, i think you can always code it to work around these issues. But in
this case, I don't see why not have them both in the same block.



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

yep, check the patch I sent, works on vanilla.

cheers



> *Gesendet:* Montag, 21. September 2015 um 23:05 Uhr
> *Von:* "Alexandre Torres Porres" <porres at gmail.com>
> *An:* "Christof Ressi" <christof.ressi at gmx.at>, "Miller Puckette" <
> mpuckett at imusic1.ucsd.edu>, "pd-list at lists.iem.at" <pd-list at 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 at 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 at gmail.com>
>> *An:* "Christof Ressi" <christof.ressi at gmx.at>, "pd-list at lists.iem.at" <
>> pd-list at 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 at 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 at gmail.com>
>>> *An:* "Christof Ressi" <christof.ressi at gmx.at>, "pd-list at lists.iem.at" <
>>> pd-list at 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 at 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 at gmail.com>
>>>> *An:* "pd-list at lists.iem.at" <pd-list at lists.iem.at>, "Christof Ressi" <
>>>> christof.ressi at 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
>>>>
>>>
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