dsp.c

一个很好用的MPEG1/4的开源编码器的应用程序

/* 
 *    dsp.c
 *
 *	Copyright (C) Vivien Chappelier - 2000
 *
 *  This file is part of fame, a free MPEG encoder.
 *	
 *  fame is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2, or (at your option)
 *  any later version.
 *   
 *  fame is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *   
 *  You should have received a copy of the GNU General Public License
 *  along with GNU Make; see the file COPYING.  If not, write to
 *  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. 
 *
 */

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <linux/soundcard.h>
#include <sys/time.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <pthread.h>

#include "types.h"
#include "dsp.h"

input_dsp_context_t *dsp_init(void)
{
  int format;
  int caps;
  audio_buf_info info;
  int i;
  input_dsp_context_t *dsp;

  dsp = (input_dsp_context_t *) malloc(sizeof(input_dsp_context_t));

  if((dsp->fd = open("/dev/dsp", O_RDONLY)) < 0) {
    perror("/dev/dsp");
    free(dsp);
    return(NULL);
  }

  /* Reset he DSP */
  if(ioctl(dsp->fd, SNDCTL_DSP_RESET, 0) < 0) {
    perror("SNDCTL_DSP_RESET");
  }

  /* Set 16 bit signed audio format */
  i = AFMT_S16_LE;
  if(ioctl(dsp->fd, SNDCTL_DSP_SETFMT, &i) < 0) {
    perror("SNDCTL_DSP_SETFMT");
    free(dsp);
    return(NULL);
  }

  /* Set mono */
  i = 0;
  if(ioctl(dsp->fd, SNDCTL_DSP_STEREO, &i) < 0) {
    perror("SNDCTL_DSP_STEREO");
    free(dsp);
    return(NULL);
  }

  /* Set frequency */
  i = 44100;
  if(ioctl(dsp->fd, SNDCTL_DSP_SPEED, &i) < 0) {
    perror("SNDCTL_DSP_SPEED");
    free(dsp);
    return(NULL);
  }

  return(dsp);
}

void dsp_close(input_dsp_context_t *dsp)
{
  close(dsp->fd);
}

int dsp_read(input_dsp_context_t *dsp, void *buffer, int size) {
  return(read(dsp->fd, buffer, size));
}