1 /*

     2  *     $Id: recording.c,v 1.1.1.1 2008-04-28 17:32:53 mbroeker Exp $

     3  * $Source: /development/c/demos/recording.c,v $

     4  *

     5  * Program to illustrate /dev/dsp device

     6  * Records several seconds of sound, then echoes it back.

     7  * Runs until Control-C is pressed.

     8  */

     9 

    10 #include <unistd.h>

    11 #include <fcntl.h>

    12 #include <sys/types.h>

    13 #include <sys/ioctl.h>

    14 #include <stdlib.h>

    15 #include <stdio.h>

    16 #include <linux/soundcard.h>

    17 

    18 #define LENGTH 3                /* how many seconds of speech to store */

    19 #define RATE 8000               /* the sampling rate */

    20 #define SIZE 8                  /* sample size: 8 or 16 bits */

    21 #define CHANNELS 1              /* 1 = mono 2 = stereo */

    22 

    23      /*

    24       * this buffer holds the digitized audio

    25       */

    26 unsigned char buf[LENGTH * RATE * SIZE * CHANNELS / 8];

    27 

    28 int main (int argc, char **argv)

    29 {

    30     int fd;                     /* sound device file descriptor */

    31     int arg;                    /* argument for ioctl calls */

    32     int status;                 /* return status of system calls */

    33 

    34     /*

    35      * open sound device

    36      */

    37 

    38     if (argc != 2) {

    39         printf ("Usage: %s <DEVICE>\n", argv[0]);

    40         printf ("Example: %s /dev/dsp\n", argv[0]);

    41         printf ("Example: %s /dev/dsp1\n", argv[0]);

    42         return EXIT_SUCCESS;

    43     }

    44 

    45     fd = open (argv[1], O_RDWR);

    46     if (fd < 0) {

    47         perror ("open of sound device failed");

    48         return EXIT_FAILURE;

    49     }

    50 

    51     /*

    52      * set sampling parameters

    53      */

    54     arg = SIZE;                 /* sample size */

    55     status = ioctl (fd, SOUND_PCM_WRITE_BITS, &arg);

    56     if (status == -1)

    57         perror ("SOUND_PCM_WRITE_BITS ioctl failed");

    58     if (arg != SIZE)

    59         perror ("unable to set sample size");

    60 

    61     arg = CHANNELS;             /* mono or stereo */

    62     status = ioctl (fd, SOUND_PCM_WRITE_CHANNELS, &arg);

    63     if (status == -1)

    64         perror ("SOUND_PCM_WRITE_CHANNELS ioctl failed");

    65     if (arg != CHANNELS)

    66         perror ("unable to set number of channels");

    67 

    68     arg = RATE;                 /* sampling rate */

    69     status = ioctl (fd, SOUND_PCM_WRITE_RATE, &arg);

    70     if (status == -1)

    71         perror ("SOUND_PCM_WRITE_WRITE ioctl failed");

    72 

    73     while (1) {                 /* loop until Control-C */

    74         printf ("Say something:\n");

    75         status = read (fd, buf, sizeof (buf));  /* record some sound */

    76         if (status != sizeof (buf))

    77             perror ("read wrong number of bytes");

    78         printf ("You said:\n");

    79         status = write (fd, buf, sizeof (buf)); /* play it back */

    80         if (status != sizeof (buf))

    81             perror ("wrote wrong number of bytes");

    82         /*

    83          * wait for playback to complete before recording again

    84          */

    85         status = ioctl (fd, SOUND_PCM_SYNC, 0);

    86         if (status == -1)

    87             perror ("SOUND_PCM_SYNC ioctl failed");

    88     }

    89     return EXIT_SUCCESS;

    90 }