pitch shifting using Fourier transform and the Propeller 1
In today's episode of SCIENCE!!!, I am considering building a pitch shifter using a PCM5102 DAC, an MCP4725 ADC, and a Propeller 1 development board, in a similar vein to the Digitech Drop pedal, the ultimate goal of which would be to create a pedal based interface that would allow me to change the tuning of my guitar in a live setting. The interface would use pushbutton switches to change parameters on the pedal, LEDs or an LCD to provide visual feedback, and a 3 pole double throw "Stomp" switch to bypass the pedal when not in use.
I know that the Coyote pedal exists, which uses a similar concept. I also know that the Spin objects in question would require Fourier transform math in order to accomplish the pitch shift, as well as Spin objects to drive the ADC and DAC, but I do have some other questions.
*Would I need to build a preamp to amplify the incoming signal in order to facilitate the conversion?
*How many Cogs would I need in order to implement this?
*What external components would be required for this, other than what is mentioned above, the input and output jacks, and possibly an SD card reader?
*What kind of Audio latency can I expect from this?
*Has anything like this been tried before? I know that there are folks that have experimented with the Prop 1 for MIDI applications, not so sure about straight audio.
*Are there any sample Spin objects that can be modified in order to facilitate this?
Edit: I realized after writing this that the MCP4725 is actually a DAC. Mea Culpa. I'll be searching for an actual audio ADC as I conduct my experiments.