[PD] Video synthesizer emulation

Off Screen offscreen at personalreport.it
Fri Jul 13 11:10:12 CEST 2012

Ed: I don't really get what is your conversion for, can you elaborate a bit
Tim: I've been already using [pix_sig2pix~] :)

That said, thanks to rdz and matju on IRC I've managed to solve the high
frequency issue. Actually the problems were two: me considering a crazy
thing to set a sample rate in the mhz domain and the hardcoded limitation
in the portaudio api of 2 mhz (if you go past this value it will reset the
sample rate without telling you, that's why my first experiments were

Right now [pix_sig2pix~] is now working as aspected, 1 mhz frequency is
enough to have all the vertical bars and stuff. I'll need to fine tune
[block~] but I think it will work quite nicely in the end.

Thanks everybody for the help!

2012/7/12 tim vets <timvets at gmail.com>

> 2012/7/12 tim vets <timvets at gmail.com>
>> [sig2pix~] ?
>> sorry, that shoulld be: [pix_sig2pix~]
>> 2012/7/12 Off Screen <offscreen at personalreport.it>
>>>  Hello everybody,
>>> I'm trying to emulate an analogue video synthesizer using GEM. My
>>> starting point is the LZX system, an old school analogue video synth which
>>> has been rebuilt today using modern circuitry components. Obviously that
>>> wonderful tool is way too expansive for me so I thought I could build
>>> something similar using Pd.
>>> My first goal is to succesfully emulate the Video Waveform Generator:
>>> http://www.youtube.com/watch?v=pbpFgvttBZw
>>> Here is a detailed description:
>>> http://www.lzxindustries.net/modules/video-waveform-generator
>>> I've tried to use [pix_sig2pix~], it works quite nicely and the patterns
>>> I get are almost identical to the ones in the video (including all the fm
>>> and pwm stuff). The problems are in the second part of the video, when they
>>> use high frequencies (~ 3mhz) to generate vertical bands. I'm pretty sure I
>>> can't use the same approach with Pd.
>>> The other option would be to use GLSL shaders, but it has two major
>>> drawbacks: first, it won't be using raw signal but control messages (no
>>> sound generation); second, it won't be patchable, once the parameters are
>>> converted into an image all the informations about frequencies are lost and
>>> I won't be able to use it to modulate another shader.
>>> I'd like to know from somebody who has much more experience than me what
>>> would be the best approach. Are there any limitations or constraints within
>>> the [pix_sig2pix~] object or Pd itself that I should be aware of? Any
>>> advice will be extremely appreciated.
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