Does some live audio processing of guitar input. Features:
- Compressor
- Distortion
- Looping
- Metronome
cargo run --release [--bpm]
This program creates JACK clients with ports that must be connected using a JACK server management tool. It expects midi input to control the looping and effects. With the current configuration of constants in src/lib.rs:
C2 through B3 are loop "registers" pressing one of these keys will start recording a loop at that register is it is empty, start playing a loop if it is stopped, and stop playing a loop if it is active. This all happens on the start of the next measure. Loop index 0, or C2, is the metronome. To stop recording the loop a midi event for pressing the sustain pedal is expected. A loop continues recording until the end of the current measure. Loops are active immediately after they are recorded and will play on the next measure.
These can be altered by changing constants in lib.rs but default settings are:
To toggle distortion: midi note 95 (B6)
To toggle compressor: midi note 96 (C7)
Number of loops: 24, midi notes 36 (C2) to 59 (B3)
JACK Audio Connection Kit
- Maybe improve compressor algorithm?
- Better distortion algorithm?
- Create TUI
- Make metronome use different output port?
There aren't any formal tests but running the application and using it seems to run with the current configuration. When I broke things it crashes fairly quickly as this application is fairly simple. I am not sure how I would simulate usage to write automated tests for this application.
I originally planned to do Wah as well but realized I need a pedal with some sort of modulation and creating that hardware wasn't reasonable right now. Making the looping mechanism turned out to be much more difficult than I expected and the solution I came up with doesn't seem incredibly robust. I learned a lot about audio and JACK, though, and am excited to do more audio related projects.
Overall, I am satisfied that it works as well as it does. Working with live signals is different from any other development I have experienced. If I were to do it again I am not sure what I would change structurally, but I am sure it could be much better.
I am very unsatisfied with the distortion effect I came up with, it sounds like garbage. I tried a few different approaches and they were all terrible with weird aliasing. I read a few papers about modeling effects of analog circuits but they were all beyond my comprehension. I could try to minimize the aliasing with oversampling techniques but this wont improve the otherwise low quality of the effect and might not even be reasonable in a live setting. The rest of the code has some TODO comments where I had thoughts of making changes or improvements but they are quite specific.
MIT License
Copyright (c) 2020 Austen Jay Nelson
See license file.