VMS 80 Style Pitch Control
Again, I've had a really productive evening of development. Earlier today while having a smoke it came to me how Neumann and Flo are able to nestle grooves and only have a Land specification (no Base Pitch). Once you understand the trick, and it is very much a magicians trick, it is painfully obvious and simple to implement. I was wayyyyyy overthinking it previously. As I said in the video last night, I thought it was a very complex calculation. I also thought it would be an iterative process whose process time would depend on the complexity of the two segments being aligned. Nope! Feel free to comment below and see if you know how its done. I'll answer right or wrong.
I also fixed how I was displaying waves. Now, the top row of Quarter Turns have the wave displayed vertically mirrored to last night. This way it actually looks like how the groove would when you look at the four quarter turns on top. And, with the Fifth or overlap quarter turn under the first, it is a much better approximation of how the groove overlaps itself after 5 quarter turns.
Couple things to note... I haven't been processing the audio with Inverse RIAA recording curve. So, I will need to do that. I'll also need to adjust some constants after that happens. Additionally, I have not implemented any concept of depth control. I'm displaying out of phase results in the rendered grooves and respecting that data in the pitch calculations. But, I've not implemented a correction routine yet. I still have some questions about this topic myself. So, I need to do a little more digging before I can actually implement that. But, once I get some answers, writing that code will be very simple.
Upcoming videos should show me doing the filtering, depth corrections, porting to the VST Effect, communicating pitch and depth values to the USB eval board, creating two PWM signals from those values, and finally driving motors. Stay Tuned!