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bsp2 / VeeSeeVSTRack

Open-source virtual modular synthesizer
http://vcvrack.com/
BSD 3-Clause "New" or "Revised" License
259 stars 29 forks source link

bsp scanner "post" section #30

Open rafaelferreiraql opened 3 years ago

rafaelferreiraql commented 3 years ago

Yes, I'm still using VeeSeeVST! So, I've been reading up on the available modules, and this paragraph from bsp's own Scanner module caught my attention.

The post section is activated by pluggin a cable into the post output. It's basically an experiment where I wanted to hear how the shape window sounds when applied to audio data. I left it in since it turned out to be useful for synthesizing cymbal and hihat sounds (among other things). The knob selects the window shape (same as the main shape parameter), and the switch toggles a window offset (this used to be a bug in earlier versions but it sounded nice with some sounds).

I don't really get what that all means. What's the shape window applied to audio data? If the regular window shape appears to be affecting the Post output, does the knob add up to that shape window? ...And how can I synthesize cymbals with it, if I may ask?

From what I've understood (if anything), the Post output seems to be intended for position modulation feedback, so I can change the post window shape (?) without affecting the regular window shape, but there's a lot I don't understand.

bsp2 commented 3 years ago

Connecting the POST output activates a ring buffer (32 frames) which is filled with the OUT sample frames. The POST shape (controlled by the knob next to the POST output) is then applied to the ring buffer content and written to the POST output.

This is simply an experimental feature that could have been moved to a completely different module. So yes, it's a bit confusing.

There are a few examples patches in the release, btw (e.g. BSP scanner cy 1.vcv or BSP scanner hh 1.vcv).

The POST shape knob and offset switch (bottom left) basically give you different flavours of noise in these patches. And yeah, it aliases a lot so it makes a big difference which note is played. Makes nice sampler-fodder, though :-)

rafaelferreiraql commented 3 years ago

Ooh I haven't tried to dive into the example patches! Thanks for the tip!

I'm not sure if I understand the whole deal. The "shape" knob for the main output affects how the 16 inputs are scanned but, if the post shape knob is described as the same but for the "post" section, how would that work with the buffer? Do each of the frames/samples act as one input for the regular scanner? That's what I gather from it but I don't know if I'm on the right track.

bsp2 commented 3 years ago

There are two shape knobs: The first one controls the weights of the regular inputs, the second one (near the POST output) controls the weights of the sample frames in the output ringbuffer. The POST section is basically a 32-tap FIR filter whose coefficients (sample weights) are controlled by the (lower) shape knob.