[PD] sampstoms~ (was Re: weird behavior of [vd~] in phave vocoder (overlapping subpatches))

[Alexandre Torres Porres]

one thing related to what was discussed on that thread.

[cyclone/sampstoms~] and [cyclone/mstosamps~] will convert between ms and
samples account for the oversampling  of the overlaps in block

so it'll consider [block~ 2048 4] to have 4x the sample rate of what pd is
running.

This actually works great if you want to use that to feed ms to [vd~] and
[vline~], which need to be corrected for that matter. I still think
[vline~], [vd~], [phasor~] and all could behave in a way that they didn't
need to be corrected... but... whatever, at least documenting this is
important.

equally, it'd be nice to either change or document  [cyclone/sampstoms~]
and [cyclone/mstosamps~] (a minor mention or demo in the help file should
do it).

Do you get this Fred? Need me to help you with that? Here's a patch
attached.

cheers

2015-09-12 20:22 GMT-03:00 Alexandre Torres Porres <porres at gmail.com>:

> > But [vd~] itself does nothing regarding to overlap and that's
> > very important to understand. It just behaves like [tabread4~].
>
> I still like considering vd~ special, but I totally see and understand
> what you mean ;)
>
> > I think this is just an issue of proper documentation!
>
> Agreed, we should ask miller to document this somewhere ;)
>
> Have you tried listening to the difference by listening to the delay lines?
>
> I was testing something about these delays and I'm actually getting some
> parallel issues, I might and should open a new thread to discuss them.
>
> One last thing from the original post,. We've sorted the delay times and
> everything, but I was also asking why we have to multiply for the interval
> ratio to get the hop difference between the two windows in the phase
> vocoder.
>
> In fact, I actually know why, and the question needs to be rephrased. The
> proper question would have been why it DOESN'T have to multiply by the
> ratio in the other patch that wasn't a phase vocoder (if you go back to my
> very first attachment you'll see I had two patches and I was comparing
> them, this was one of the issues).
>
> And you "didn't have to" multiply it because it was working fine... But
> the truth is that it works better if you multiply it by the ratio, and it
> just can go unnoticed because it's not a phase vocoder, so it doesn't ruin
> things as is the case with the phase vocoder.
>
> Isn't it great to have it all sorted?
>
> Thanks for your great help
>
> ps. I noticed your last reply was off the list, so I got us back to settle
> and close the thread.
>
>
>
> 2015-09-12 6:23 GMT-03:00 Christof Ressi <christof.ressi at gmx.at>:
>
>> > But the point is, [tabread4~] won't automatically do anything, unlike
>> [vd~]. At least that is how I see it.
>>
>> Hmmm... maybe you might have to go back to my explanation of point 1) and
>> see how the overlapping only works fine all the time because the state of
>> the delay line outside the subpatches happens to change synchroniously with
>> the time the input buffer is taken for one of the overlapping windows.
>> Window2 will get the input buffer one hope size time later than window1,
>> and in that same time the delay line itself has moved for the same amount
>> of samples. So after overlapping again at the output, everything is fine
>> again. But [vd~] itself does nothing regarding to overlap and that's very
>> important to understand. It just behaves like [tabread4~].
>>
>> You're last patch shows that you fully understand how oscillators and
>> ramps work in overlapping subpatches. I've attached a patch where you can
>> have a look how a delay line actually looks like inside such a subpatch.
>> You can also see that a samplewise delay like [z~] (or [delay~]) is
>> equivalent to a sorted pair of [delwrite~] and [delread~] and acts the same
>> way. I've exchanged [vd~] for [delread~] to get rid of the problem with
>> index 0.
>>
>>
>> > or, in the meantime, can you explain why using a delay~ line is
>> different as you understand it? I mean, what problems does it generate and
>> all?
>>
>> So you from checking my patch you can see that they actually behave the
>> same way! In the case of my [cpitchshift~] patch, the difference arises
>> from the fact, that the [vd~] acts on a delay line outside the subpatch
>> where [z~] is a delay line which is fully located inside the subpatch. Note
>> that the delay time in samples is 1/4 window size, so it's 1 hop size and
>> doesn't create discontiuities. It is just a lazy way to guarantee that the
>> back window is 1 hop size behind :-). The problem only is: When you change
>> the pitch at a certain point of time, the buffer of [z~] has been filled at
>> a time where that pitch change has not occured yet. But after one window
>> calculation it's fine again (unless you've again changed the pitch and so
>> on...).
>>
>>
>> > But then, I kinda think this is a bug! Not only a [vd~] bug, but also
>> [vline~] and [phasor~] / [osc~] (regarding frequency).
>>
>> Well, the oversampling is happening, if you want it or not :-). And I
>> think 1 second always should have as many samples as the sampling rate. I
>> guess most of the misunderstandings come from the fact that the
>> oversampling itself is not documented properly... and that [samplerate~]
>> behaves unlogically!
>> The phase correction for oscillators and ramps could be done internally
>> in the objects, but then this might lead to other weird behaviour instead
>> so it's kind of a trade off. Again, I think this is just an issue of proper
>> documentation!
>>
>> Cheers
>>
>>
>> *Gesendet:* Freitag, 11. September 2015 um 20:55 Uhr
>> *Von:* "Alexandre Torres Porres" <porres at gmail.com>
>> *An:* "Christof Ressi" <christof.ressi at gmx.at>
>> *Cc:* Pd-List <pd-list at lists.iem.at>
>> *Betreff:* Re: Re: Re: Re: Re: [PD] weird behavior of [vd~] in phave
>> vocoder (overlapping subpatches)
>> "*So when you send 1000 ms to a [vd~] in a subpatch with overlap 4, the
>> delay line will be read at sample 176400 (supposing the [delwrite~] is in a
>> subpatch with sample rate 44100). This is not an issue if both the
>> [delwrite~] and [vd~] are in the same subpatch. But if they are in
>> subpatches with different sample rates you have to make some adjustments.
>> If you're also aware of this behaviour than I don't know what else we
>> could've missed...*"
>>
>> Yeah, I wasn't really aware of this, and it seems to settle the whole
>> doubt about why do we have to divide all time values by the overlap with
>> [vd~].
>>
>> I surely had an idea that it made sense, but not exactly why, and now
>> that you've explained how time in ms is converted internally to sample
>> number it makes sense.
>>
>> But then, I kinda think this is a bug! Not only a [vd~] bug, but also
>> [vline~] and [phasor~] / [osc~] (regarding frequency).
>>
>> I still need to come back about the need to multiply for the window size
>> in order to back down an overlap, and wether using delay~ lines instead of
>> that is the exact same thing or wether is just not perceptually
>> different... just wait...
>>
>> or, in the meantime, can you explain why using a delay~ line is different
>> as you understand it? I mean, what problems does it generate and all?
>>
>> thanks
>>
>>
>> 2015-09-11 15:38 GMT-03:00 Alexandre Torres Porres <porres at gmail.com>:
>>>
>>> Thanks for the detailed explanation. It was very clear. A couple of
>>> other remarks, in 1) and 2) you have an output that is 4 times greater
>>> because they add up. If I'd used delread~ in 2) I'd have thought it was ok
>>> :) - it was weird to me why it wasn't working but now I get it.
>>>
>>> I had an idea why 1) worked, as I was saying from the beginning and we
>>> know well, it does the overlapping fine without discontinuities. So I was
>>> saying it dealt fine with overlapping, we can say it does it
>>> "automatically".
>>>
>>> Now, back to my saying how [vd~] and [tabread4~] behave differently.
>>> Attached I have an oscillator that was recorded into a buffer/array. Then
>>> I'm reading it from overlapping subpatches. So, now, there are
>>> discontinuities. They don't work the same way, and that was my point.
>>>
>>> I'm reading it with [tabplay~] and [tabread4~] driven by [vline~] (which
>>> has to be 4x faster for it to work).
>>>
>>> But then, as we also know, the deal is how [vline~] drives it. It'll
>>> generate a line without discontinuities and on the way out they'll be
>>> overlaped and added, and this ruins things. Same happens automatically in
>>> [tabplay~], no need for vline~ to ruin it.
>>>
>>> On the other hand, we can force [vline~] to overlap and make it alright.
>>>
>>> But the point is, [tabread4~] won't automatically do anything, unlike
>>> [vd~]. At least that is how I see it.
>>>
>>> But again, that is not what's most important about sorting out my patch,
>>> and now that this seems fine, I should get back to trying to sort that from
>>> the beginning all over again. Hopefully with more idea of what's going on.
>>>
>>> cheers
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>> 2015-09-11 7:18 GMT-03:00 Christof Ressi <christof.ressi at gmx.at>:
>>>>
>>>> Luckily I can offer you (hopefully) clear explanations for all three
>>>> cases :-). Here we go:
>>>>
>>>> First some background information: In an subpatch with overlap 4, the
>>>> input and output buffers are overlapping, but internally the calculation of
>>>> the 4 windows happens sequentially. This is why a [phasor~] from a parent
>>>> patch will pass the subpatch unchanged (only the amplitude is four times
>>>> because of the summing), while a [phasor~] inside will look messed up after
>>>> the outlet. Ok, I know you know all this. But all this also applies to
>>>> delay lines. Now let's examine the three cases:
>>>>
>>>> 1) the [delwrite~] is in the parent patch. Let's suppose we have a
>>>> blocksize of 8 and overlap 4 (thus hopsize of 2). Because the [delwrite~]
>>>> is in the parent patch, it is just treated the same way as something coming
>>>> from the inlet. [vd~] reads the index 1 of the ringbuffer at the following
>>>> points of time:
>>>>
>>>> window 1: ----- 0    1   2    3    4     5     6    7
>>>> window 2: ----- 2    3   4    5    6     7     8    9
>>>> window 3: ----- 4    5   6    7    8    9    10   11
>>>> window 4: ----- 6    7   8    9   10  11   12  13
>>>>
>>>> Window2 reads 2 samples later than window1, window3 reads 2 samples
>>>> later than window2 and so on... If you overlap and sum it at the outlets,
>>>> you end up with everything aligned in the right way. This is exactly the
>>>> reason why you don't get any discontinuties.
>>>>
>>>> 2) both the [delwrite~] and [vd~] are in the subpatch. The delay line
>>>> inside the subpatch is written the following way:
>>>>
>>>> 0 1 2 3 4 5 6 7 (,) 2 3 4 5 6 7 8 9 (,) 4 5 6 7 8 9 10 11 (,) 6 7 8 9
>>>> 10 11 12 13 (,) 8 9 10 11 12 13 14 15 etc... where the numbers again
>>>> represent points of time in the input buffer.
>>>>
>>>> So the 4 windows are written sequentially into the delay line, because
>>>> internally window calculation happens sequentially (as I've mentioned
>>>> above). So there are indeed discontinuities which you have to take care of.
>>>> Now suppose you reed the delay line at index 0 for each window:
>>>> Because the delay line is constantly running, window 1 might start from
>>>> 0, window 2 then starts from 2 (because it's calculated after window1, so
>>>> in the meantime the ring buffer has moved by 8 samples), window3 from 4,
>>>> window4 from 6 etc... If you do the overlap, the delay line is again
>>>> preserved.
>>>> But what if you don't read at the ring buffer at index 0 for all
>>>> windows? Suppose [vd~] reads from index 7, than the output for window1
>>>> would be 6 7 2 3 4 5 6 7, window2 would be 8 9 4 5 6 7 8 9, so the output
>>>> is messed up!
>>>> Now if you think of it, the condition for preserving the delay line is
>>>> setting the index of [vd~] to a multiple of the hop size. Only then each
>>>> window will read a sequence from the buffer that is continious.
>>>> But wait, why didn't it work for you? It's just because in your patch
>>>> [vd~] was set to 0, but it can't read from index 0, instead it will read
>>>> from index 1, which screws everything up because it's not a multiple of the
>>>> hop size. I added sum message boxes where you can try out some good and
>>>> some bad numbers.
>>>> BTW: this behaviour of [delwrite~] inside an overlapping subpatch is
>>>> also the reason why you have to multiply the maximum buffer size by the
>>>> overlap factor, because it needs four times as much samples. Additionally
>>>> this explains why for a spectral delay, the delay time must be a multiple
>>>> of the window size time and not the hop size time, because only that way
>>>> continuity is garanteed.
>>>>
>>>> 3) This is just as messed up as I predicted, because you're simply
>>>> 'reading along' the 'weird' delay line above. :-)
>>>>
>>>> Don't worry, it took me some time to figure this all out, because this
>>>> is nowhere documented explicitly, it just follows implicitely from the
>>>> behaviour of overlapping subpatches (which is also not documented properly
>>>> at all... the oversampling and sequential calculation should be mentioned
>>>> in the helpfile of [block~] at least --> possible bug fix?)
>>>>
>>>> Tell me if that makes sense to you. When I find some time I could make
>>>> a nice graphic visualizing these issues in a better way.
>>>>
>>>> Cheers
>>>>
>>>>
>>>>
>>>> *Gesendet:* Freitag, 11. September 2015 um 08:06 Uhr
>>>> *Von:* "Alexandre Torres Porres" <porres at gmail.com>
>>>> *An:* "Christof Ressi" <christof.ressi at gmx.at>
>>>> *Cc:* Pd-List <pd-list at lists.iem.at>
>>>> *Betreff:* Re: Re: Re: Re: [PD] weird behavior of [vd~] in phave
>>>> vocoder (overlapping subpatches)
>>>> I had said
>>>>
>>>> "*So I was thinking and then thought that the other patch was working
>>>> because it wasn't a phase vocoder, so the phase alignment was not
>>>> important. But now that you say this and showed your patch, I can see that
>>>> you need not worry if you are using a delay. And I was actually using a
>>>> delay in my non fft patch.*
>>>>
>>>> *In the end my patches were different but equivalent and now I get why.
>>>> It's cool to know and learn that if you are using delay you don't need to
>>>> care about it.*"
>>>>
>>>> And I was just wrong! I wasn't using a delay line in the same way you
>>>> were. I just confused.
>>>>
>>>> And the more I dig, the more my head hurts and the more confused I
>>>> am... I guess I'm back to square one...
>>>>
>>>> Or worse, I guess I have more doubts now than at first :)
>>>>
>>>> My first surprise was to see that if you had a delread~ in a parent
>>>> patch and a [vd~] into a subpatch with overlap is that it wouldn't generate
>>>> discontinuities... and I'm not sure why is that...
>>>>
>>>> Now, you say
>>>>
>>>> "*Having [delwrite~] and [vd~] in the same overlapping subpatch (as
>>>> you would in a spectral delay) is also not a problem. But having the
>>>> [delwrite~] in the overlapping subpatch and the [vd~] outside will cause
>>>> weirdness :-).*"
>>>>
>>>> And I tested it. And hmm, I'm not sure what you mean, cause it only
>>>> works when you have a delread~ in a parent patch and a [vd~] into a
>>>> subpatch with overlap. I do have spectral delay patches and they just work,
>>>> but if you are listening to what comes out of both delread~ and vd~ in a
>>>> subpatch, it's just bad.
>>>>
>>>> Check my attached patch. I don't really get why it works in the first
>>>> one and it doesn't in the other two. Maybe this is a first step before
>>>> venturing into the other implications of all this mess ;)
>>>>
>>>> cheers
>>>>
>>>>
>>>>
>>>> 2015-09-10 22:53 GMT-03:00 Christof Ressi <christof.ressi at gmx.at>:
>>>>>
>>>>> Thanks for testing! I was suspecting that the difference might only be
>>>>> a very subtle one. But I'll check as well in next days. BTW: Your 'speed'
>>>>> control looks very cool, I'm gonna try this myself.
>>>>>
>>>>> I think I understand your questions better now, so I'll try to give
>>>>> some more concrete answers again:
>>>>>
>>>>> > My point was just that [vd~] acts in a special way when in an
>>>>> overlapping subpatch, and that is it'll output the audio
>>>>> > without discontinuities or pitch shifting because of interpreting
>>>>> the overlap as oversampling. That behaviour is special
>>>>> > when compared to [osc~], [phasor~]
>>>>>
>>>>> I don't understand what you mean here. [osc~] and [phasor~] also
>>>>> interpret the overlap as oversampling, as do all objects which rely on time
>>>>> information (ms, hz). In fact, overlapping is achieved by oversampling. The
>>>>> reason why there won't be any discontinuities with [vd~] is because it is
>>>>> only a reading object like [tabread4~] and the delay line itself is not
>>>>> affected by the overlapping. You only have to be careful when dealing with
>>>>> milliseconds and different sample rates. Having [delwrite~] and [vd~] in
>>>>> the same overlapping subpatch (as you would in a spectral delay) is also
>>>>> not a problem. But having the [delwrite~] in the overlapping subpatch and
>>>>> the [vd~] outside will cause weirdness :-).
>>>>>
>>>>> There are actual two 'problems' with [phasor~], [osc~] and [vline~] in
>>>>> overlapping subpatches:
>>>>>
>>>>> 1) looking from the outside they seem to run too slowly because they
>>>>> rely on a higher sample rate within in the subpatch, but contrary to
>>>>> deliberate upsampling, e. g. [block~ 64 1 4], the output doesn't get
>>>>> downsampled at the outlets. So with overlap 4 the sample rate is 176400 Hz
>>>>> instead of 44100 Hz. That means a [phasor~] with a speed of 44100 Hz has a
>>>>> period of 4 samples. When it goes through the outlets it still has a period
>>>>> of 4 samples but now the sample rate is 44100 Hz and its 'speed' is
>>>>> therefore interpreted as only 11025 Hz. You also have to be careful with
>>>>> milliseconds because they also depend on the sample rate.
>>>>> (Oddly enough, [samplerate~] always outputs the global samplerate and
>>>>> not the actual rate the subpatch is running at. This is why there is the
>>>>> [iem_samplerate~] object in iemlib, which always gives the actual
>>>>> samplerate.)
>>>>>
>>>>> 2) they run continously across blocks but because of overlapping they
>>>>> are not phase aligned after the outlet.
>>>>>
>>>>> The oversampling is the only reason for all the corrections you had to
>>>>> do in you patch. I attached a copy where I made some comments. I hope this
>>>>> helps. If you have any more questions you can ask me.
>>>>>
>>>>> Cheers
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> *Gesendet:* Donnerstag, 10. September 2015 um 23:00 Uhr
>>>>> *Von:* "Alexandre Torres Porres" <porres at gmail.com>
>>>>> *An:* "Christof Ressi" <christof.ressi at gmx.at>
>>>>> *Cc:* Pd-List <pd-list at lists.iem.at>
>>>>> *Betreff:* Re: Re: Re: [PD] weird behavior of [vd~] in phave vocoder
>>>>> (overlapping subpatches)
>>>>> naaah, yeah, they're different.. oops... but doesn't really make any
>>>>> difference perceptually... let me check it some more...
>>>>>
>>>>> 2015-09-10 17:49 GMT-03:00 Alexandre Torres Porres <porres at gmail.com>:
>>>>>
>>>>>>
>>>>>> yeah, I have to sit again with some time and figure it out, I should
>>>>>> do some tests to better understand how many objects behave. But, in the
>>>>>> meantime, lets talk about something important here.
>>>>>>
>>>>>> > Delaying the back window [z~] is a rather lazy trick and it won't
>>>>>> > give accurate results each time you change the pitch shifting
>>>>>> > factor, but after one fft-window it settles. The question is if you
>>>>>> > can actually here this error. When I find some time I'll make a
>>>>>> > comparison between our both solutions.
>>>>>>
>>>>>> Are you really sure about this? Cause I've been testing it and
>>>>>> thinking about it and, in my opinion, both are exactly the same thing,
>>>>>> equally equivalent, and I can't hear any difference as well.
>>>>>>
>>>>>> Lets sort this out ;)
>>>>>>
>>>>>> I think that the second delay makes it a simpler patch and easier to
>>>>>> understand. I'm using [cyclone/delay~] by the way, which works with samples
>>>>>> - must be the same thing as [z~].
>>>>>>
>>>>>> cheers
>>>>>>
>>>>>> 2015-09-10 14:23 GMT-03:00 Christof Ressi <christof.ressi at gmx.at>:
>>>>>>>
>>>>>>> Hmmm, since we basically agree on all these things I was thinking if
>>>>>>> I missed a point, because I simply don't believe that [vd~] behaves
>>>>>>> differently than [tabread4~] and there is any unlogical or 'special'
>>>>>>> behaviour with [vd~] within an upsampled subpatch. Maybe one thing: The
>>>>>>> input of [vd~] is a time in milliseconds which is interpreted according to
>>>>>>> the actual sample rate (because internally the delay lines work on samples,
>>>>>>> of course). In that way it behaves like [phasor~], [vline~], [osc~]. So
>>>>>>> when you send 1000 ms to a [vd~] in a subpatch with overlap 4, the delay
>>>>>>> line will be read at sample 176400 (supposing the [delwrite~] is in a
>>>>>>> subpatch with sample rate 44100). This is not an issue if both the
>>>>>>> [delwrite~] and [vd~] are in the same subpatch. But if they are in
>>>>>>> subpatches with different sample rates you have to make some adjustments.
>>>>>>> If you're also aware of this behaviour than I don't know what else we
>>>>>>> could've missed...
>>>>>>>
>>>>>>> Cheers
>>>>>>> *Gesendet:* Donnerstag, 10. September 2015 um 18:10 Uhr
>>>>>>> *Von:* "Alexandre Torres Porres" <porres at gmail.com>
>>>>>>> *An:* "Christof Ressi" <christof.ressi at gmx.at>
>>>>>>> *Cc:* Pd-List <pd-list at lists.iem.at>
>>>>>>> *Betreff:* Re: Re: [PD] weird behavior of [vd~] in phave vocoder
>>>>>>> (overlapping subpatches)
>>>>>>> yeah, it'll consider the signal input is 0 so it'll output the
>>>>>>> corresponding index - which is "1" because of the interpolation.
>>>>>>>
>>>>>>> and yeah, I'm aware they're both buffer readers, delwrite~ / vd~
>>>>>>> being a circular / ring buffer. And my point was this difference between
>>>>>>> them, where delay lines will always read/output at regular speed.
>>>>>>>
>>>>>>> But that is not the core of the discussion, and we actually agree on
>>>>>>> it, so I'm not sure what we're talking about here.
>>>>>>>
>>>>>>> My point was just that [vd~] acts in a special way when in an
>>>>>>> overlapping subpatch, and that is it'll output the audio without
>>>>>>> discontinuities or pitch shifting because of interpreting the overlap as
>>>>>>> oversampling. That behaviour is special when compared to [osc~], [phasor~]
>>>>>>> and I also tried a buffer reader like [tabplay~] and got "bad" results.
>>>>>>> They all don't work well in it, and so does not [vline~] by the way. There
>>>>>>> might be other relevant objects to test but I'm just not thinking about it.
>>>>>>> Nevertheless, I have the idea most will have problems, while some, like
>>>>>>> [vd~], will be be fine.
>>>>>>>
>>>>>>> The thing about [tabread~] is that it solely depends on external
>>>>>>> sources to read the buffers, while [vd~] doesn't, and that makes quite a
>>>>>>> practical difference in my opinion. The deal with [tabread~] is that the
>>>>>>> issue is more about what object is driving it and how it behaves (such as
>>>>>>> [vline~] and [phasor~], which don't behave well with overlapping
>>>>>>> subpatches).
>>>>>>>
>>>>>>> But again, not a relevant discussion. But I do feel like making more
>>>>>>> tests, I just don't know if there is a possible to test to check how the
>>>>>>> behaviour or [vd~] and [tabread4~] could relate between themselves.
>>>>>>>
>>>>>>> > For me its sometimes a trial and error game to find all
>>>>>>> > those parameters which have to be divided/multiplied
>>>>>>> > by the overlap factor. But after a while of thinking
>>>>>>> > everything turns out to make sense.
>>>>>>>
>>>>>>> yeah, it was trial and error, but I'm still not 100% sure how it
>>>>>>> makes sense... hence this thread :) - but I guess I'll keep thinking more
>>>>>>> about it.
>>>>>>>
>>>>>>> > Delaying the back window [z~] is a rather lazy trick and
>>>>>>> > it won't give accurate results each time you change the
>>>>>>> > pitch shifting factor,
>>>>>>>
>>>>>>> that's important to note, and that's why miller's patch may not have
>>>>>>> been using this procedure.
>>>>>>>
>>>>>>> thanks
>>>>>>>
>>>>>>>
>>>>>>> 2015-09-10 6:39 GMT-03:00 Christof Ressi <christof.ressi at gmx.at>:
>>>>>>>>
>>>>>>>> "Oops, now I'm the one to say you can't compare them as equal. You
>>>>>>>> see, [tabread~] needs to have an audio input to read through the array, but
>>>>>>>> [vd~] is always "reading" the buffer at normal speed - so this makes them
>>>>>>>> quite different. Since [tabread~] only react if some signal is feeding it,
>>>>>>>> then it depends solely on that incoming signal; and thus the object who's
>>>>>>>> outputting it, which could be [phasor~] or [vline~]. So it's more about
>>>>>>>> which object who's driving it than itself."
>>>>>>>>
>>>>>>>> Again, I insist that the behaviour of [tabread4~] and [vd~] is
>>>>>>>> equivalent ;-). When you don't feed any input to [tabread4~] it outputs the
>>>>>>>> value at index 1. Now try to think of a delay line as simply a table which
>>>>>>>> content is constantly updated at a time interval of 1/SR (SR = the actual
>>>>>>>> sample rate of the subpatch containing the [delwirte~]). If you don't send
>>>>>>>> any signal to [vd~], it behaves just as [tabread4~], only that the value at
>>>>>>>> index 1 always changes, so it only appears that [vd~] itself is reading
>>>>>>>> along a buffer. (Note that both objects can't read index 0 because of the
>>>>>>>> 4-point interpolation algorithm. So with [vd~] you will never get less than
>>>>>>>> a one sample delay.)
>>>>>>>> To make sloppy analogy:  [tabread4~] would be a band machine where
>>>>>>>> the tape itself stands still why the tape head can be freely moved, whereas
>>>>>>>> [vd~] would be one where the tape runs at a fixed speed and additionally
>>>>>>>> the tape head can be moved too. Well, I don't know if this makes sense :-).
>>>>>>>>
>>>>>>>> Since you took the word "reading" in quotation marks you might be
>>>>>>>> aware of all this. In that case the confusion might arise from the fact
>>>>>>>> that you have to consider the relation between the 'speed' of the delay
>>>>>>>> line (depending on the sample rate of the subpatch containing the
>>>>>>>> [delwrite~]) and the 'speed' of the object providing the input for the
>>>>>>>> [vd~].
>>>>>>>>
>>>>>>>> Please anyone correct me if I'm wrong on these points!
>>>>>>>>
>>>>>>>> For me its sometimes a trial and error game to find all those
>>>>>>>> parameters which have to be divided/multiplied by the overlap factor. But
>>>>>>>> after a while of thinking everything turns out to make sense.
>>>>>>>> Delaying the back window [z~] is a rather lazy trick and it won't
>>>>>>>> give accurate results each time you change the pitch shifting factor, but
>>>>>>>> after one fft-window it settles. The question is if you can actually here
>>>>>>>> this error. When I find some time I'll make a comparison between our both
>>>>>>>> solutions.
>>>>>>>>
>>>>>>>> Cheers, Christof
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> *Gesendet:* Donnerstag, 10. September 2015 um 07:51 Uhr
>>>>>>>> *Von:* "Alexandre Torres Porres" <porres at gmail.com>
>>>>>>>> *An:* "Christof Ressi" <christof.ressi at gmx.at>
>>>>>>>> *Cc:* Pd-List <pd-list at lists.iem.at>, "Gerd Schuller" <
>>>>>>>> studio at gerdschuller.com>
>>>>>>>> *Betreff:* Re: [PD] weird behavior of [vd~] in phave vocoder
>>>>>>>> (overlapping subpatches)
>>>>>>>> >>> unlike [osc~], [vd~] will get the continuities between blocks
>>>>>>>> right!"
>>>>>>>>
>>>>>>>> > You can't really compare these two objects.
>>>>>>>>
>>>>>>>> Sure I can :) i'll insist on it by the way. Again, [vd~] will not
>>>>>>>> generate discontinuities with the overlaps, unlike other objects such as
>>>>>>>> [osc~] and [phasor~]. Moreover, and as a logical result, it won't change
>>>>>>>> the pitch because of the oversampling. It'll just work fine.
>>>>>>>>
>>>>>>>> > [vd~] is actually the same thing as [tabread4~]
>>>>>>>>
>>>>>>>> Oops, now I'm the one to say you can't compare them as equal. You
>>>>>>>> see, [tabread~] needs to have an audio input to read through the array, but
>>>>>>>> [vd~] is always "reading" the buffer at normal speed - so this makes them
>>>>>>>> quite different. Since [tabread~] only react if some signal is feeding it,
>>>>>>>> then it depends solely on that incoming signal; and thus the object who's
>>>>>>>> outputting it, which could be [phasor~] or [vline~]. So it's more about
>>>>>>>> which object who's driving it than itself.
>>>>>>>>
>>>>>>>> When it comes to [vd~], the pithc shifting and time stretching also
>>>>>>>> depends on the object that's driving the input, which could be again
>>>>>>>> [phasor~] or [vline~] and need to deal with their behaviour.
>>>>>>>>
>>>>>>>> > you have to divide by the overlap factor, because then
>>>>>>>> > you read less samples and therefore virtually slow the
>>>>>>>> > [vline~] down. In a subpatch with overlap 4 everything
>>>>>>>> > happens 4 times as fast because instead of only 1 block
>>>>>>>>
>>>>>>>> yeah, sure, I've pointed it in my 1st message. I get that.
>>>>>>>>
>>>>>>>> But as I asked, I don't really get how ALL parameters need to
>>>>>>>> divided by 4, not only the [vline~] time, that is not clear yet. Sorry.
>>>>>>>>
>>>>>>>> And by the way, my patch does also time stretching, so it's
>>>>>>>> different than yours and is dealing with more parameters and issues than
>>>>>>>> you. So you are addressing the [vline~] issue only (replaced by [phasor~]
>>>>>>>> in your patch) - but that was the only parameter that I really understood
>>>>>>>> anyway.
>>>>>>>>
>>>>>>>> > When using [z~] to delay the back window simply by the
>>>>>>>> > fft hop size you don't have to care about  window sizes
>>>>>>>>
>>>>>>>> hmm, my problem was more why were my two patches different, the one
>>>>>>>> with fft needed to care about it, but the other one didn't. I actually get
>>>>>>>> why that thing needs to be done to properly phase align the windows.
>>>>>>>>
>>>>>>>> So I was thinking and then thought that the other patch was working
>>>>>>>> because it wasn't a phase vocoder, so the phase alignment was not
>>>>>>>> important. But now that you say this and showed your patch, I can see that
>>>>>>>> you need not worry if you are using a delay. And I was actually using a
>>>>>>>> delay in my non fft patch.
>>>>>>>>
>>>>>>>> In the end my patches were different but equivalent and now I get
>>>>>>>> why. It's cool to know and learn that if you are using delay you don't need
>>>>>>>> to care about it.
>>>>>>>>
>>>>>>>> thanks
>>>>>>>>
>>>>>>>> ps. I'm still curious on sorting out the behaviour of [vd~] though
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> 2015-09-09 7:54 GMT-03:00 Christof Ressi <christof.ressi at gmx.at>:
>>>>>>>>>
>>>>>>>>> Hi Alexandre,
>>>>>>>>>
>>>>>>>>> I'm new on this list, but I think I can help you on this because
>>>>>>>>> recently I tried to do the same thing. I can't fully test your patch
>>>>>>>>> because I'm missing the cyclone library (and don't bother to install it
>>>>>>>>> :-p).  I try to give an answer to the following questions:
>>>>>>>>>
>>>>>>>>> "Other issues related to overlapping besides this "oversampling"
>>>>>>>>> is that some objects won't make it right, they'll chop the blocks with
>>>>>>>>> discontinuities, such as the case with [osc~]. But as it turns out, unlike
>>>>>>>>> [osc~], [vd~] will get the continuities between blocks right!"
>>>>>>>>>
>>>>>>>>> You can't really compare these two objects. [vd~] is actually the
>>>>>>>>> same thing as [tabread4~], only that it reads from a ring buffer rather
>>>>>>>>> from a table. So the critical thing is only which object you use as the
>>>>>>>>> input for [vd~]. You are using [vline~] whereas I'm using [phasor~]. Both
>>>>>>>>> are equivalent. For the reading index for [vd~] you have to divide by the
>>>>>>>>> overlap factor, because then you read less samples and therefore virtually
>>>>>>>>> slow the [vline~] down. In a subpatch with overlap 4 everything happens 4
>>>>>>>>> times as fast because instead of only 1 block, 4 blocks have to be
>>>>>>>>> processed - in the same time!). My approach is to have a [phasor~] run from
>>>>>>>>> 0 to 1 (or 1 to 0) for every block so I have to multiply it's speed by
>>>>>>>>> four. Than I multiply the output by the windows size. Note that in my patch
>>>>>>>>> I get the second window one hop size behind by simply delaying it with [z~]
>>>>>>>>> whereas you've chosen to use a second [vd~] with a wrapping object. (I
>>>>>>>>> guess you're way actually saves some memory as you don't need a second
>>>>>>>>> delay line).
>>>>>>>>>
>>>>>>>>> "And even more weirdly, in the Pvoc patch I have to multiply the
>>>>>>>>> difference between the front and back windows to the ratio of
>>>>>>>>> transposition. This is even crazier than the last issue, and I have no idea
>>>>>>>>> why that has to be this way..."
>>>>>>>>>
>>>>>>>>> When you're transposing you're actually reading more samples for
>>>>>>>>> upwards pitchshifting and less samples for downwards pitchshifting. So you
>>>>>>>>> basically stretch or compress the window size. This means also that the
>>>>>>>>> time difference between two windows changes if you want them to be phase
>>>>>>>>> aligned. If the window gets larger, the time difference to the last window
>>>>>>>>> also gets larger and vice verca. You might be aware of this: The window in
>>>>>>>>> the back has to be phase aligned with the front window because you need it
>>>>>>>>> as a reference to calculate the difference from the actual phase of the
>>>>>>>>> previous output window.
>>>>>>>>>
>>>>>>>>> When using [z~] to delay the back window simply by the fft hop
>>>>>>>>> size you don't have to care about window sizes and time differences at all.
>>>>>>>>> It is, however, also a bit incorrect for the first analysis window after a
>>>>>>>>> change of pitch so I might change it and try it your way!
>>>>>>>>>
>>>>>>>>> You can have a look at my solution and compare it to yours. From
>>>>>>>>> what I've seen both work the same way though I couldn't test your patch.
>>>>>>>>> However, I think that my patch could be conceptually easier to understand,
>>>>>>>>> but I might be wrong :-).
>>>>>>>>>
>>>>>>>>> Cheers, Christof
>>>>>>>>>
>>>>>>>>> PS: Ignore the right half of [pd read-windows] with the two
>>>>>>>>> [tabread4~], this is only needed for the freeze effect.
>>>>>>>>>
>>>>>>>>
>
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