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

[Alexandre Torres Porres]

in max, these objects won't convert differently in overlapping subpatches
for fft, so it's a global pd thing, it'll interfere in the way many objects
work, like vline~ / phasor~ / whatever... sampstoms~ is just another one,
but it may be come in hand to deal with wrong time computations.

anyway, maybe leave it as it is, or maybe a mention in the help file would
be nice.

cheers

2015-09-12 20:32 GMT-03:00 Alexandre Torres Porres <porres at gmail.com>:

> 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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