Live coding with Sporth and Vim

2016-08-01

This past month, I've been working on improving live coding in Sporth. At the moment, these improvements only apply to Linux users who use JACK. If you happen to fall in this category, read on...

The Before Times

Prior to this month, live coding in Sporth was a hacked together thing I did. After code re-evaluation was made possible in Sporth, I quickly wrote a small utility called "jacksporth" which not only could run Sporth patches in realtime with JACK audio, but could also re-compile Sporth strings via OSC. I used this utility with Vim and some shell scripts to create a live coding environment for myself.

This worked well enough, but it had many limitations. Comments did not work and would "short circuit" and disable anything which came after it. The command line interface was really awkward, not utilizing any command line flags from the standard sporth command line utility. jacksporth had read a file, even it was nothing.

The Better Times

How do you make a Sporth live coding better? I will tell you, in bullet point form:

merge the "jacksporth" utility into the sporth CLI (as optional, of course)
add the sporth vim keybindings and shell scripts to the util folder instead of a random folder on my computer
add an option to start sporth without a file
give the ability to change p-values over OSC
give the ability to process one channel of realtime audio input using the "in" ugen
give the ability to spawn multiple instances of sporth in realtime

All of the above improvements have made it much easier to get started live coding!

Setup

Firstly, you'll need to make sure you have JACK and liblo installed. If you plan on using Vim, you'll need to ensure that you have installed oscsend, a commandline tool which should have come installed with liblo. All of these dependencies are needed on top of the usual dependencies for Sporth.

Next, you'll need to enable jack. In config.mk, uncomment the line that says "BUILD_JACK=1". Then run "make clean", "make", and "sudo make install"..

Inside the util folder, there is a file called sporth.vim. Place this in the directory where you intend to do live coding.

Running

To start Sporth for live coding, go into the directory you plan to run code on, and run the following command:

 sporth -b jack -c 2 -0

Next, open up Vim and run ":so sporth.vim"(sporth.vim should be in the current working directory).

Now write some sporth code:

 (
 440 0.5 sine
 dup
 )

This code can be evaluated by pressing space+s.

Alternate instances of Sporth

Any number of sporth instances can spawned. My current Sporth + Vim live coding setup has key bindings for two instances. To start the alternate instance, run this command:

 sporth -o alternate -p 6450 -b jack -c 2 -0

This will create a jack client called "alternate", with an OSC server on port 6450. IIn the vim setup, code can be evaluated to this alternate instance with they keyboard shortcut space+l.

Audio input

The "in" ugen in Sporth has been overridden to take in one audio input from JACK.

For instance:

 in 0.8 0.75 dup delay 0.5 * + dup

Adds a feedback delay to an input signal. Clock and gate signals also work in addition to audio signals.