We need to expirement with modifying the following files:

  /rockbox/firmware/pcm_playback.c
  /rockbox/firmware/pcm_record.c

We want to modify dma_start to drop the input audio to our function to phase shift the input audio, and then drop the shifted audio to dma for audio output.

We can create a plugin for this whole thing, or we can rip into the Rockbox code directly
Pros of a plugin:

• Not modifying existing code
• Less risk in tearing up code that is depended upon by other modules or code that could crash Rockbox

Cons of a plugin: * Possible performance limited * Possibly more difficult to integrate other functions that will run threads in parallel with our plugin

We could also re-implement the Rockbox code directly:
Pros of direct code modification:

• Potentially faster code execution
• More flexibility with how our version of Rockbox could run since we wouldn't be limited to how Rockbox handles plugins only

Cons of direct code modification:

• Could easily break the whole system if code is modified that is depended upon by other code we don't know about
• May not save much in processing speed, or could even negatively impact already optimized Rockbox code