[PD] pix2sig and back

cyrille henry ch at chnry.net
Tue Oct 24 13:32:02 CEST 2017

Le 24/10/2017 à 13:18, Peter P. a écrit :
> Hi list,
> I am trying to convert an audio signal to pixel data using pix_sig2pix~
> and then back to audio data using pix_pix2sig~ without further
> manipulations. Please see attached patch.
> I do scale the audio signal from -1 to 1 to lie in a range compliant
> to pixel data, which I assume to be 0 to 1.
> Not having connected an input to the subpatch, this signal will hence be
> 0.5 and will display in the red color channel.
> Converting that red channel back to audio signals and doing the opposite
> scaling operation, I am getting a 51dB constant signal at the output
> even without having attached a signal to the input of pix_sig2pix~.
> Checking with a snapshot~ object indicates a constant signal of 0.003921
> I assume this to be due to limited resolution numbers in the pixel data
> and wonder what their resolution is?

8 bits / channels

so resolution is 1/256 = 0.0039...

You can code MSB in Red, and LSB in green is you want 16 bits...

> Then I texture the pixel data onto a rectangle. This rectangle
> does flicker and flip diagonally from time to time and I wonder if it is
> an error on my machine only and where it could come from.

I don't see any flicker in your patch. (linux / intel GPU)


> Also, I am getting an error message in the Pd console upon creating a
> single pix_sig2pix~ object in an empty patch:
> 	GEM: Someone sent a bogus pointer to copy2Image
> and am curious if this red error message is related to the above problem...
> Thank you for all ideas and advice!
> Peter
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