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

[Alexandre Torres Porres]

here's another example, there's a delay line with a size of 2048 samples,
in patch with a block size of 2048, and the delay line is only able to
delay a maximum of 64 samples

2015-09-22 14:07 GMT-03:00 Alexandre Torres Porres <porres at gmail.com>:

>
>
> 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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