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 <[email protected]>: > 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. >>>>>>>>>> >>>>>>>>> >> > > _______________________________________________ > [email protected] mailing list > UNSUBSCRIBE and account-management -> > http://lists.puredata.info/listinfo/pd-list > >
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