anchor.diff:                                (lambda (sink)
                                   (buffer-empty sink))
                                 *sinks*))
  +               (when (endp *sinks*)
  +                 (setf (sup:event-state *sinks-present-event*) nil))
                  ;; Samples have been consumed, wake fillers.
                  (mezzano.supervisor:condition-notify *sink-cvar* t)
                  ;; Leave the card running.
  
positive.code: (defvar *cards* '())
  
  (defvar *sinks* '())
  (defvar *sink-lock* (mezzano.supervisor:make-mutex "Sound output sink lock"))
  (defvar *sink-cvar* (mezzano.supervisor:make-condition-variable "Sound output sink cvar"))
  
  (defvar *master-volume* 1.0)
  
  
negative.code:     total-copied))
  
  (defgeneric sound-card-run (card buffer-fill-callback))
  (defgeneric sound-card-presence-event (card)
    (:method (card) nil))
  
  (defun refill-sound-output-buffer (buffer start end)
    (check-type buffer (simple-array single-float (*)))
  