The problem is though: I don't have a clue, where to start. I have your basic knowledge in C and SDL, but that's pretty much it
I admire your enthusiasm, but, If I had a pound / euro / dollar for every time I’ve seen similar posts on forums, by people who think that that somehow qualifies them to write plugins, I’d make considerably more money than the little I do from actually writing plugins…
To someone who has spent a long time learning how to (I hope) get this right, this trivialises what is a very complex discipline.
I don’t want to be negative, or discouraging - but if you want to write anything useful (other than a simple ‘gain’ plugin, and its possible to get that wrong in more ways than you might imagine possible, then you will need to spend a lot of time learning about the DSP that makes real plugins work before attempting anything or it will be a complete waste of time.
The GUI is optional but…
I prefer the complete consistency between plugin UIs that LADSPA gives you as well
That’ll be the same consistency that makes LADSPA UIs look completely different on different hosts (and sometimes on different versions of the same host) or at best renders all the controls in such a ‘generic’ way that it’s impossible to quickly identify one grey / blue slider from another - especially when some controls just have arbitary parameters (e.g. EQ frequency 0… to 1.0)
For a simple EQ or Gain it might just be ok, but I wonder how easy it would be to use something like my graphical EQ without the custom UI (ten bands, three parameters per band, and on / off / filter type for each band - so, well in excess of thirty sliders, which all look the same and are probably rendered in some completely arbitary order)
Some of the SWH LADSPA plugins are incredibly simple
Which is why almost all of the ones I’ve tried have some ‘warning’ about not doing something or other with them which might cause them to blow up or go unstable - in fairness, as I understand it, the SWH plugins were mostly designed as some very basic building blocks, but with all due respect, I would hesitate to recommend them as a template for a (professional) plugin design.
One type of plugin that is severely lacking in our community is a spectrum analyser plugin
True - and it would be a great addition to the stock of LV2 plugins (when I last looked at adding some similar functionality to my graphical EQ, I found that there was a significant problem with transfering the FFT data between the plugin UI and the DSP code using the LV2 mechanisms available. (I hope) that may have changed now, in which case it wouldn’t be too difficult for someone with DSP experience to do (but it’s also not too difficult for someone without DSP experience to get it badly wrong)