[PD] pd book sprint

Alexandre Porres porres at gmail.com
Mon Mar 30 17:43:27 CEST 2009


Hi D.

Yeah, DC Offset could be covered in what is digital Audio, or maybe briefly
mentioned. The thing is that it needs patches to explain and show how
adjusting the DC Offset works.
I know things must be kept as simple as possible, but not simpler than that,
because it could be misleading. I had that problem myself when teaching with
Floss Manuals, students had doubts why the square and sawtooth oscilators
were different, or "wrong".

The DC Offset is an extremely important parameter that should be a part of
the synthesizer section of Floss Manuals. It could also be a part of the
Amplitude Modulation Examples. Actually, changing DC Offset is all it needs
to change from an Amplitude Modulation to a Ring Modulation. So having a DC
Offset parameter there can explain the differences between the two.

For instance, I find the osc7.pd example really misleading. At first, it is
supposed to be a Ring Modulation instead of an Amplitude Modulation, since
there is no DC offset in the modulator sigal. But, as the sawtooth wave
oscilator has a DC Offset (that shouldnt be tghere anyway, and it is not
even mentioned), it is actually an Amplitude modulation after all, with the
Remark that the Carrier signal has the role of the Modulator signal, and Not
the carrier signal itself. So, in any way (either presenting it as a Ring
Modulation or Amplitude Modulation) corrections should be made.

So I dont see a way of not editing these patches, because it could be even
more confusing if we would write a disconected chapter that complements and
gives the tools to correct things that could have been presented before.

I just don't see how simplicity here compensates the misleading way the
theory is presented.

The DC Offset is the main problem I see in Floss Manuals. And I actually
give my students an altered version of Floss Manuals to work with because of
that. I am developing a book of my own that complements well with the Floss
Manuals, but I still need to do make this Remark.

I could show my book, but it is in Portuguese only, so far...

by the way, we have people in Brazil who would like to collaborate and
translate this to portuguese.

I can send you a triangle wave oscilator right away.

cheers
alex


On Mon, Mar 30, 2009 at 11:56 AM, Derek Holzer <derek at umatic.nl> wrote:

> Actually, DC offset could be covered in "What is Digital Audio", since it
> is a concept that needs explaining. Then, my suggestion still is to include
> it after the basics of the Square Waves. I'd like to keep the patches there
> as simple as possible, and since the DC Offset can be done at the end, why
> not have it there?
>
> Triangle wave would also be good. Write it first and we'll see where
> exactly to put it.
>
> D.
>
>
> Alexandre Porres wrote:
>
>> sure, I could do both.
>>
>> But I think it would be inportant to start just after
>>
>>    * AUDIO TUTORIALS
>>    * SimpleSynthIntroduction
>>      <http://en.flossmanuals.net/PureData/SimpleSynthIntroduction>
>>
>>
>> and before the oscilators with the Short DC offset chapter.
>>
>> Then edit and correct the oscilator patches with values from -1 to 1
>>
>> I also can create and put in the oscilator chapter a Triangle wave
>> oscilator made with phasor
>>
>> what do you say?
>>
>> Cheers
>>
>>
>> On Mon, Mar 30, 2009 at 11:43 AM, Derek Holzer <derek at umatic.nl <mailto:
>> derek at umatic.nl>> wrote:
>>
>>    Alexandre,
>>
>>    Yes please, get on board!
>>
>>    In the case of the square wave chapter, I had assumed that doing it
>>    with digital logic would result in either 0 (no amplitude) or 1
>>    (full amplitude). So there shouldn't be any DC offset when it's at
>>    0. Of course, there are some other real-world problems with those
>>    patches, namely that there is also no antialiasing.
>>
>>    Since the FLOSS Manuals are "modular", they can be remixed as needed
>>    for any kind of workshop, class or curriculum, including or leaving
>>    out sections from all the different FLOSS Manuals as needed.
>>
>>    So my suggestion to you would be to write a short chapter on DC
>>    offset which can then be referred to in the square wave tutorial, or
>>    in any other tutorial or manual where such a situation might arise.
>>
>>    Likewise, I'd love it if someone could do a single chapter on the
>>    different antialiasing methods (Miller's, Frank's...). The idea
>>    would be to simplify the explanations so that one doesn't need a
>>    background in DSP or computer science in order to understand them.
>>
>>    Would you be interested to do either of those?
>>
>>    D.
>>
>>    Alexandre Porres wrote:
>>
>>        Hi, I am really interested in helping!
>>
>>        I actually have some stuff I wanted to "corrrect", or bring some
>>        attention to, like the DC OFFSET. You dont cover it, and when
>>        you show how to get a Square Wave, the DC Offset is not properly
>>        adjusted.
>>
>>        thanks
>>
>>        cheers
>>
>>        On Mon, Mar 30, 2009 at 11:20 AM, Derek Holzer <derek at umatic.nl
>>        <mailto:derek at umatic.nl> <mailto:derek at umatic.nl
>>
>>        <mailto:derek at umatic.nl>>> wrote:
>>
>>           Hey Alexandre,
>>
>>           I just posted the announcement of the Pd FLOSS Manuals Book
>>        Sprint:
>>
>>
>> http://lists.puredata.info/pipermail/pd-list/2009-03/069107.html
>>
>>           I was wondering if you'd be interested to help out next
>>        weekend? It
>>           shouldn't be a problem to contribute remotely, and it would
>>        really help
>>           build up the momentum to finish this manual.
>>
>>           Have a look over the topics and see if there is anything
>>        you'd like to
>>           cover and let me know.
>>
>>           Best!
>>           Derek
>>
>>           --    ::: derek holzer ::: http://blog.myspace.com/macumbista:::
>>           http://www.vimeo.com/macumbista :::
>>           ---Oblique Strategy # 11:
>>           "Always first steps"
>>
>>
>>
>>
>>
>>        --        Alexandre Torres Porres
>>        cel. (11)8179-6226
>>        Website: http://porres.googlepages.com/home
>>        http://www.myspace.com/alexandretorresporres
>>
>>
>>    --    ::: derek holzer ::: http://blog.myspace.com/macumbista :::
>>    http://www.vimeo.com/macumbista :::
>>    ---Oblique Strategy # 109:
>>    "Lost in useless territory"
>>
>>
>>
>>
>> --
>> Alexandre Torres Porres
>> cel. (11)8179-6226
>> Website: http://porres.googlepages.com/home
>> http://www.myspace.com/alexandretorresporres
>>
>>
> --
> ::: derek holzer ::: http://blog.myspace.com/macumbista :::
> http://www.vimeo.com/macumbista :::
> ---Oblique Strategy # 67:
> "Emphasize the flaws"
>



-- 
Alexandre Torres Porres
cel. (11)8179-6226
Website: http://porres.googlepages.com/home
http://www.myspace.com/alexandretorresporres
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