A small subset of ALSA interface for Common Lisp.
PCM streams are encapsulated in ALSO-ALSA:PCM-STREAM instances.
To play random noise on one channel of default stereo device:
(defconstant +buffer-size+ 256)
(defconstant +sample-rate+ 8000)
(defconstant +channels+ 2)
(also-alsa:with-alsa-device (pcm "sysdefault" +buffer-size+ '(signed-byte 16) :direction :output
:channels-count +channels+ :sample-rate +sample-rate+)
(also-alsa:alsa-start pcm)
(loop repeat 2 do
(loop with buffer = (also-alsa:buffer pcm)
for pos from 0 below (* +channels+ (also-alsa:buffer-size pcm)) by (* 2 +channels+)
for sample = (coerce (- (random 65535) 32767) '(signed-byte 16)) do
(setf (aref buffer pos) (logand sample #xff))
(setf (aref buffer (1+ pos)) (logand (ash sample -8) #xff))
(multiple-value-bind (avail delay) (also-alsa:get-avail-delay pcm)
(also-alsa:alsa-write pcm)))))