I recently wanted to play with some procedural audio generation in Racket. So, after some research, I found that there’s a port of the cross-platform audio I/O library Portaudio. However, installing it through raco was not doing the job for me, on Windows. I investigated the issue and figure a problem with the compiled libraries that were out of date with the Racket interface and then I rebuilt it and submitted to another repository. I created a Pull Request but still hasn’t been accepted.
There were very few people with the same issue, I imagine manipulating raw audio buffers in interpreted languages with garbage collectors is not really popular, but I hope this can help someone.
The main portaudio repo is fine, it’s just the dependent repo with the specific binary library for the Windows system that is broken, so we need to explicitly install that from my repository first:
raco pkg install https://github.com/CrociDB/portaudio-x86_64-win32.git
Then finally install portaudio. The dependency will be ignored, since it’s already installed:
raco pkg install portaudio
Packets can be installed through DrRacket as well, just by hitting File -> Install Package. But remember to do in the same order.
Running the Example
There are examples for both realtime streams and pre-allocated buffer play on the port docs page. And playing the copy version should work out of the box:
#lang racket
(require portaudio
ffi/vector)
(define pitch 426)
(define sample-rate 44100.0)
(define tpisr (* 2 pi (/ 1.0 sample-rate)))
(define (real->s16 x)
(inexact->exact (round (* 32767 x))))
(define vec (make-s16vector (* 88200 2)))
(for ([t (in-range 88200)])
(define sample (real->s16 (* 0.2 (sin (* tpisr t pitch)))))
(s16vector-set! vec (* 2 t) sample)
(s16vector-set! vec (add1 (* 2 t)) sample))
(s16vec-play vec 0 88200 sample-rate)