[PD] Video synthesizer emulation

Ed Kelly morph_2016 at yahoo.co.uk
Thu Jul 12 19:44:42 CEST 2012

Perhaps a good place to start is to work out what the aliased value of 3.2MHz is - i.e. when you divide 3.2MHz by the number of lines over which the signal is spread (625 for the PAL system).
Patch enclosed,
Gemnotes-0.1alpha: Live music notation for Pure Data

 From: Off Screen <offscreen at personalreport.it>
To: pd-list at iem.at 
Sent: Thursday, 12 July 2012, 18:20
Subject: [PD] Video synthesizer emulation

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:

Here is a detailed description:

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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