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 <[email protected]>: > > 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 <[email protected]>: > >> > 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" <[email protected]> >> *An:* "Christof Ressi" <[email protected]> >> *Cc:* Pd-List <[email protected]> >> *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 <[email protected]>: >>> >>> 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 <[email protected]>: >>>> >>>> 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" <[email protected]> >>>> *An:* "Christof Ressi" <[email protected]> >>>> *Cc:* Pd-List <[email protected]> >>>> *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 <[email protected]>: >>>>> >>>>> 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" <[email protected]> >>>>> *An:* "Christof Ressi" <[email protected]> >>>>> *Cc:* Pd-List <[email protected]> >>>>> *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 <[email protected]>: >>>>> >>>>>> >>>>>> 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 <[email protected]>: >>>>>>> >>>>>>> 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" <[email protected]> >>>>>>> *An:* "Christof Ressi" <[email protected]> >>>>>>> *Cc:* Pd-List <[email protected]> >>>>>>> *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 <[email protected]>: >>>>>>>> >>>>>>>> "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" <[email protected]> >>>>>>>> *An:* "Christof Ressi" <[email protected]> >>>>>>>> *Cc:* Pd-List <[email protected]>, "Gerd Schuller" < >>>>>>>> [email protected]> >>>>>>>> *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 <[email protected]>: >>>>>>>>> >>>>>>>>> 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. >>>>>>>>> >>>>>>>> >
sampstoms.pd
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