Multi-channel oscilloscope implementation

[mmontag]

Hi @tildearrow, I was wondering if you could describe your approach for exposing the per-channel scope data in Furnace. I've started reading code but it would help to have a brief high-level description.

I know this requires modification of emulation cores; @yoyofr has done similar work for the cool Modizer mobile app.

[tildearrow]

Brief desc of approach:

1. DivDispatch provides function to get chan osc
2. Emu cores modified to expose chan out
3. DivDispatch::acquire() collects chan outs and stores them into osc buffers
4. GUI gets osc bufs
5. Data is passed to FFTW
6. Phase info of fundamental is extracted and used to align waveform

[mmontag]

Thanks. Nice alignment technique. How do you determine the fundamental frequency?

[mmontag]

Cool, I found https://github.com/tildearrow/furnace/blob/master/src/gui/chanOsc.cpp#L456

You find the bin with max magnitude, with a scaling function (y=1/x^0.8) that favors low-frequency bins.
Nit: seems like the sqrt on line 462 is unnecessary, no?

[mmontag]

@tildearrow could you point to a representative commit where an emu core was modified to expose chan out?