[PD] oscilloscope raster with audio signals
Derek Holzer
macumbista at gmail.com
Sat Aug 25 20:06:33 CEST 2018
A suggestion from Johannes Taelman solved the issue:
"Make sure the number of audio samples used per scanline is a whole number."
Thanks for having a look in any case!
Derek
On 25/08/2018 20.44, Derek Holzer wrote:
> Dear Pd folks,
>
> I've written about this before here, and I still have not found a
> solution. I've been chasing the same bug in my Vector Synthesis code for
> a year now. The purpose of this code is to draw a "video raster" on an
> X/Y oscilloscope screen with audio signals from a DC coupled MOTU audio
> interface. The brightness of this raster will be modulated by
> information from [pix_data]. Because I am redrawing the raster from
> scratch and the pix information is not tied to the video frame/line rate
> at all, this raster can be of arbitrary frame rate and line numbers
> which remain within audio range. This part works fine and I have no
> questions about that.
>
> My problem is with creating the raster. No matter how I create my raster
> signals, I get the same phase-related offset on my horizontal lines. The
> amount of offset is dependent on the relationship between the vertical
> and horizontal rate. You can see this in the video linked at the bottom
> of this email. Please view that before posting any replies.
>
> The Pure Data patch I am using, which includes three different equally
> flawed methods of making this raster, is available at:
>
> http://macumbista.net/wp-content/uploads/2018/08/oscilloscope-raster-test.txt
>
>
> (Change .txt extension to .pd)
>
> Video demo is here:
>
> https://vimeo.com/286687337/0b865bd76c
>
> I'm guess there is something in the DSP that I have overlooked. I'm also
> guessing it will take some kind of guru to work it out. If you think you
> are that guru, please let me know.
>
> Thank you for your kind attention,
> Derek
--
derek holzer
noise.art.technology
http://macumbista.net
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