linux下实现录音和播放

linux下编写本地录音和播放demo测试代码：

1. 通过读.wav格式的音频流，将音频流写入DMA缓存区，实现语音播放；

2. 通过读DMA缓存区的音频流，实现录音。

首先要配置硬件参数，包括设置采样位数、通道数、采样率等，然后向DMA缓存区写或者读，实现播放和录音，具体见下文：

/************************************************************************* 
  > File Name: local_player.c 
  > Desc.    : Read from file and playback, or capture and write to file.
  > Author   : horistudio@163.com
  > Date     : 2020/05/26
 ************************************************************************/ 
/* Use the newer ALSA API */
#define ALSA_PCM_NEW_HW_PARAMS_API

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <alsa/asoundlib.h>

int main(int argc, char *argv[]) {
#if 1
  int rc;
  int size;
  snd_pcm_t *handle;
  snd_pcm_hw_params_t *params;
  unsigned int val;
  int dir;
  snd_pcm_uframes_t frames;
  char *buffer;

#if 0
  /* Open PCM device for playback. */
  rc = snd_pcm_open(&handle, "default",
                    SND_PCM_STREAM_PLAYBACK, 0);
#endif

  /* Open PCM device for capture. */
  rc = snd_pcm_open(&handle, "default",
                    SND_PCM_STREAM_CAPTURE, 0);
  if (rc < 0) {
    fprintf(stderr,
            "unable to open pcm device: %s/n",
            snd_strerror(rc));
    exit(1);
  }

  /* Allocate a hardware parameters object. */
  snd_pcm_hw_params_alloca(&params);

  /* Fill it in with default values. */
  snd_pcm_hw_params_any(handle, params);

  /* Set the desired hardware parameters. */

  /* Interleaved mode */
  snd_pcm_hw_params_set_access(handle, params,
                      SND_PCM_ACCESS_RW_INTERLEAVED);

  /* Signed 16-bit little-endian format */
  snd_pcm_hw_params_set_format(handle, params,
                              SND_PCM_FORMAT_S16_LE);

  /* Two channels (stereo) */
  snd_pcm_hw_params_set_channels(handle, params, 8);

  /* 44100 bits/second sampling rate (CD quality) */
  val = 48000;
  snd_pcm_hw_params_set_rate_near(handle, params,
                                  &val, &dir);

  /* Set period size to 32 frames. */
  frames = 32;
  snd_pcm_hw_params_set_period_size_near(handle,
                              params, &frames, &dir);

  /* Write the parameters to the driver */
  rc = snd_pcm_hw_params(handle, params);
  if (rc < 0) {
    fprintf(stderr,
            "unable to set hw parameters: %s/n",
            snd_strerror(rc));
    exit(1);
  }

  /* Use a buffer large enough to hold one period */
  snd_pcm_hw_params_get_period_size(params, &frames,
                                    &dir);
  size = frames * 4; /* 2 bytes/sample, 2 channels */
  buffer = (char *) malloc(size);
  printf("------>frames:%d, size:%d\n",frames,size);
#endif

#if 1
  	//************************[3.文件操作]*******************************
	#if 0
  /*通过主函数传参，传入.wav格式文件名*/
	FILE *fp_r 	= NULL;
	int ret 	= 0;
	fp_r = fopen(argv[1], "rb");
	if(fp_r == NULL) {
		printf("open file fail!\n");
		exit(1);
	}
	#endif

	/* 打开一个文件，将录音音频流写入文件 */ 
	FILE *fp = NULL;
	int file_len = 0;

	fp = fopen("record_dump.raw", "a+");
	if(fp == NULL) {
		printf("open file fail!\n");
		exit(1);
	}

	printf("Configurations are finished......\n");
	
    while (1) {
	  	/* 1.read from file and playback */
		 #if 0
	    //read audio file 
	    memset(buffer,0,size);
		  rc = fread(buffer, 1, size, fp_r);
	    if (rc == 0) {
	      fprintf(stderr, "end of file on input/n");
	      break;
	    } else if (rc != size) {
	      fprintf(stderr,
	              "short read: read %d bytes/n", rc);
	    }
		
	    rc = snd_pcm_writei(handle, buffer, frames);
	    if (rc == -EPIPE) {
	      /* EPIPE means underrun */
	      fprintf(stderr, "underrun occurred/n");
	      snd_pcm_prepare(handle);
	    } else if (rc < 0) {
	      fprintf(stderr,
	              "error from writei: %s/n",
	              snd_strerror(rc));
	    }  else if (rc != (int)frames) {
	      fprintf(stderr,
	              "short write, write %d frames/n", rc);
	    }
		#endif

		/* 2.capture and write to file */
		#if 1
		/* capture */
		memset(buffer, 0, size);
		rc = snd_pcm_readi(handle, buffer, frames);
	    printf("snd_pcm_readi,frames:%d, buffer:%s\n",frames, buffer);
	    if (rc == -EPIPE)
	    {
	        /* EPIPE means overrun */
	        fprintf(stderr, "overrun occurred\n");
	        snd_pcm_prepare(handle);
	    } else if (rc < 0) {
	        fprintf(stderr,
	                "error from read: %s\n",
	                snd_strerror(rc));
	    } else if (rc != (int)frames) {
          fprintf(stderr, 
	        	"short read, read %d frames\n", rc);
	    }
		
		if (fp) {
	        file_len = fwrite(buffer, 1, size, fp);
			printf("fwrite:%d bytes \n", file_len);
		 	
		} else {
		  printf("%s[%d] file open fail\n",__func__,__LINE__);
		}
		#endif
  }
#endif

  fclose(fp);
  //close(fd_f);
  snd_pcm_drain(handle);
  snd_pcm_close(handle);
  free(buffer);

  return 0;
}

*上述代码，可以根据需要解开注释或者打上注释，分别测试录音或者播放

编译时，需要引入alsa库，-L指定具体的alsa-utils-x.x.x类库的asound等，编译方法方法：

gcc -o local_player local_player.c -L XXX/alsa-utils-1.1.5 -lasound -lm -ldl

测试方法：

播放 通过喇叭是否正常播放音频文件，确认是否播放成功；

录音 通过dump出来的文件，用audiocity或其他软件打开并播放，确认录音是否正常

 

      * 上文代码的意义是可以问语音通话做准备，读取打开的.wav音频流其实是模拟读取网络发来的音频流buffer，将录音音频流写入文件是模拟向网络发送buffer写入