mci-record

Arguments: device &key from to notify-p wait-p insert-p overwrite-p

Records audio that may be saved as a .wav file by calling mci-save. device is an mci-wave-audio instance. from may be nil to default to recording at the end of the already-recorded audio on this device (if any), or else an integer indicating the starting position within the already-recorded audio (see mci-device-set-time-format and tmsf-to-integer) from which to begin overwritting. to may be either nil to default to recording indefinitely until mci-stop is called, or else a position indicating the position at which to stop recording automatically.

If the wait-p argument is specified true, this function will not return until the action is completed. If nil, this function is run asynchronously. If notify-p is true, mci-notify will be called when this function completes.

See cg-mci.htm for information about MCI support in Common Graphics.

Example

Here is a sample recording session as a series of top-level forms that may be evaluated sequentially in the IDE editor, for example. Note that mci-record returns immediately though recording continues until the mci-stop call is made. A real application would typically have widgets that make these calls.

When recording audio, a microphone or other audio input must be connected to a sound card, with a driver for that sound card selected as the default audio device in Control Panel. The sound card may have a mixer applet in which you must select the current recording input jack(s) and level.

(use-package :cg)

;; Create and open a wave audio device for recording.
(setq wav (make-instance 'mci-wave-audio))
(mci-open wav)

;; Check the default audio quality (low).
(mci-device-bits-per-sample wav) ;; ==> 8
(mci-device-samples-per-second wav) ;; ==> 11025
(mci-device-channels wav) ;; ==> 1 (monophonic)

;; Set higher quality audio before recording.
(mci-set-wave-options wav
                      :bits-per-sample 16
                      :samples-per-second 48000
                      :channels 1)   ;; still monophonic for now

;; Try a recording.
(mci-record wav)           ;; recording starts now (start talking ...)
(mci-stop wav)             ;; recording stops now
(mci-record wav)           ;; append more recording to the end
(mci-stop wav)             ;; stop again

;; Save the recording so far to a .wav file.
(mci-save wav :file "c:\\temp1.wav")

;; Play back what we've recorded.
(mci-seek wav :seek-to-start-p t)   ;; rewind to beginning
(mci-play wav)                      ;; play from current position
(mci-stop wav)                      ;; interrupt a long playback

;; Start over, re-using the same device.
(mci-delete wav)           ;; delete everything recorded so far
(mci-set-wave-options wav  ;; try a stereo recording this time
                      :bits-per-sample 16
                      :samples-per-second 48000
                      :channels 2) ;; stereo
(mci-record wav)           ;; record from scratch
(mci-stop wav)             ;; stop recording

;; Try "editing out" a middle section of the recording.
(mci-seek wav :seek-to-start-p t)    ;; rewind to beginning
(mci-play wav)             ;; play the recording for a little while
(mci-stop wav)             ;; stop in the middle of playback
(setq from (mci-device-position wav))  ;; remember where we stopped
(mci-play wav)             ;; play back a bit further
(mci-stop wav)             ;; stop playback again
(setq to (mci-device-position wav))  ;; remember where we stopped again
(mci-delete wav :from from :to to)   ;; delete the middle section
(mci-seek wav :seek-to-start-p t)    ;; rewind to beginning
(mci-play wav)             ;; play the edited recording

;; Save the edited recording over the file that was saved earlier.
(mci-save wav :file "c:\\temp1.wav")
(mci-close wav)            ;; close the device when we're done with it

Copyright (c) 1998-2022, Franz Inc. Lafayette, CA., USA. All rights reserved.
This page was not revised from the 10.0 page.
Created 2019.8.20.